mirror of
https://github.com/ThePhD/sol2.git
synced 2024-03-22 13:10:44 +08:00
330df79ab9
Added new examples to illustrate a few things people were wondering about HEAVILY fixed up usertypes and inheritance. Again. Sigh. One day it'll all be correct.
600 lines
15 KiB
ReStructuredText
600 lines
15 KiB
ReStructuredText
tutorial: quick 'n' dirty
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=========================
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These are all the things. Use your browser's search to find things you want.
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You'll need to ``#include <sol.hpp>``/``#include "sol.hpp"`` somewhere in your code. Sol is header-only, so you don't need to compile anything.
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opening a state
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---------------
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.. code-block:: cpp
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int main (int argc, char* argv[]) {
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sol::state lua;
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// open some common libraries
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lua.open_libraries(sol::lib::base, sol::lib::package);
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lua.script( "print('bark bark bark!')" );
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}
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sol::state on lua_State*
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------------------------
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For your system/game that already has lua, but you'd like something nice:
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.. code-block:: cpp
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int pre_existing_system( lua_State* L ) {
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sol::state_view lua(L);
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lua.script( "print('bark bark bark!')" );
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return 0;
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}
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running lua code
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----------------
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.. code-block:: cpp
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sol::state lua;
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// load and execute from string
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lua.script("a = 'test'");
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// load and execute from file
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lua.script_file("path/to/luascript.lua");
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// run a script, get the result
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int value = lua.script("return 54");
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// value == 54
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// load file without execute
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sol::load_result script1 = lua.load_file("path/to/luascript.lua");
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script1(); //execute
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// load string without execute
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sol::load_result script2 = lua.load("a = 'test'");
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script2(); //execute
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sol::load_result script3 = lua.load("return 24");
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int value2 = script3(); // execute, get return value
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// value2 == 24
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set and get variables
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---------------------
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You can set/get everything.
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.. code-block:: cpp
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sol::lua_state lua;
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lua.open_libraries(sol::lib::base);
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// integer types
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lua.set("number", 24);
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// floating point numbers
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lua["number2"] = 24.5;
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// string types
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lua["important_string"] = "woof woof";
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// non-recognized types is stored as userdata
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// is callable, therefore gets stored as a function
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lua["a_function"] = [](){ return 100; };
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// make a table
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lua["some_table"] = lua.create_table_wth("value", 24);
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Equivalent to loading a lua file with:
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.. code-block:: lua
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number = 24
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number2 = 24.5
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important_string = "woof woof"
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a_function = function () return 100 end
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some_table = { value = 24 }
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Retrieve these variables using this syntax:
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.. code-block:: cpp
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// implicit conversion
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int number = lua["number"];
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// explicit get
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auto number2 = lua.get<double>("number2");
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// strings too
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std::string important_string = lua["important_string"];
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// dig into a table
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int value = lua["value"]["value"];
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// get a function
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sol::function a_function = lua["a_function"];
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int value_is_100 = a_function();
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// get a std::function
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std::function<int()> a_std_function = lua["a_function"];
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int value_is_still_100 = a_std_function();
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Retrieve Lua types using ``object`` and other ``sol::`` types.
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.. code-block:: cpp
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sol::state lua;
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// ... everything from before
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sol::object number_obj = lua.get<sol::object>( "number" );
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// sol::type::number
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sol::type t1 = number_obj.get_type();
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sol::object function_obj = lua[ "a_function" ];
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// sol::type::function
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sol::type t2 = function_obj.get_type();
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bool is_it_really = function_obj.is<std::function<int()>(); // true
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// will not contain data
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sol::optional<int> check_for_me = lua["a_function"];
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You can erase things by setting it to ``nullptr`` or ``sol::nil``.
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.. code-block:: cpp
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sol::state lua;
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lua.script("exists = 250");
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int first_try = lua.get_or<int>( 322 );
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// first_try == 250
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lua.set("exists", sol::nil);
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int second_try = lua.get_or<int>( 322 );
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// second_try == 322
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Note that if its a :doc:`userdata/usertype<../api/usertype>` for a C++ type, the destructor will run only when the garbage collector deems it appropriate to destroy the memory. If you are relying on the destructor being run when its set to ``sol::nil``, you're probably committing a mistake.
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tables
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------
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:doc:`sol::state<../api/state>` is a table too.
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.. code-block:: cpp
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sol::state lua;
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// Raw string literal for easy multiline
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lua.script( R"(
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abc = { [0] = 24 }
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def = {
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ghi = {
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bark = 50,
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woof = abc
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}
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}
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)"
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);
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sol::table abc = lua["abc"];
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sol::table def = lua["def"];
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sol::table ghi = lua["def"]["ghi"];
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int bark1 = def["ghi"]["bark"];
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int bark2 = lua["def"]["ghi"]["bark"];
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// bark1 == bark2 == 50
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int abcval1 = abc[0];
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int abcval2 = ghi["woof"][0];
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// abcval1 == abcval2 == 24
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If you're going deep, be safe:
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.. code-block:: cpp
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sol::state lua;
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sol::optional<int> will_not_error = lua["abc"]["DOESNOTEXIST"]["ghi"];
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// will_not_error == sol::nullopt
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int will_not_error2 = lua["abc"]["def"]["ghi"]["jklm"].get_or<int>(25);
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// is 25
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// if you don't go safe,
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// will throw (or do at_panic if no exceptions)
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int aaaahhh = lua["abc"]["hope_u_liek_crash"];
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make tables
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-----------
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Make some:
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.. code-block:: cpp
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sol::state lua;
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lua["abc"] = lua.create_table_with(
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0, 24
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);
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lua.create_named_table("def",
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"ghi", lua.create_table_with(
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"bark", 50,
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// can reference other existing stuff too
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"woof", lua["abc"]
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)
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);
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Equivalent Lua code:
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.. code-block:: lua
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abc = { [0] = 24 }
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def = {
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ghi = {
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bark = 50,
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woof = abc
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}
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}
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You can put anything you want in tables as values or keys, including strings, numbers, functions, other tables.
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Note that this idea that things can be nested is important and will help later when you get into :ref:`namespacing<namespaceing>`.
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functions
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---------
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They're great. Use them:
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.. code-block:: cpp
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sol::state lua;
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lua.script("function f (a, b, c, d) return 1 end");
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lua.script("function g (a, b) return a + b end");
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// fixed signature std::function<...>
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std::function<int(int, double, int, std::string)> stdfx = lua["f"];
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// sol::function is often easier:
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// takes a variable number/types of arguments...
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sol::function fx = lua["f"];
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int is_one = stdfx(1, 34.5, 3, "bark");
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int is_also_one = fx(1, "boop", 3, "bark");
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// call through operator[]
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int is_three = lua["g"](1, 2);
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// is_three == 3
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double is_4_8 = lua["g"](2.4, 2.4);
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// is_4_8 == 4.8
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If you need to protect against errors and parser problems and you're not ready to deal with Lua's `longjmp` problems (if you compiled with C), use :doc:`sol::protected_function<../api/protected_function>`.
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You can bind member variables as functions too, as well as all KINDS of function-like things:
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.. code-block:: cpp
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void some_function () {
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std::cout << "some function!" << std::endl;
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}
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void some_other_function () {
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std::cout << "some other function!" << std::endl;
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}
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struct some_class {
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int variable = 30;
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double member_function () {
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return 24.5;
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}
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};
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sol::state lua;
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lua.open_libraries(sol::lib::base);
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// put an instance of "some_class" into lua
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// (we'll go into more detail about this later
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// just know here that it works and is
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// put into lua as a userdata
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lua.set("sc", some_class());
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// binds a plain function
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lua["f1"] = some_function;
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lua.set_function("f2", &some_other_function);
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// binds just the member function
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lua["m1"] = &some_class::member_function;
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// binds the class to the type
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lua.set_function("m2", &some_class::member_function, some_class{});
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// binds just the member variable as a function
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lua["v1"] = &some_class::variable;
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// binds class with member variable as function
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lua.set_function("v2", &some_class::variable, some_class{});
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The lua code to call these things is:
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.. code-block:: lua
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f1() -- some function!
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f2() -- some other function!
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-- need class instance if you don't bind it with the function
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print(m1(sc)) -- 24.5
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-- does not need class instance: was bound to lua with one
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print(m2()) -- 24.5
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-- need class instance if you
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-- don't bind it with the function
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print(v1(sc)) -- 30
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-- does not need class instance:
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-- it was bound with one
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print(v2()) -- 30
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-- can set, still
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-- requires instance
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v1(sc, 212)
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-- can set, does not need
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-- class instance: was bound with one
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v2(254)
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print(v1(sc)) -- 212
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print(v2()) -- 254
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Can use ``sol::readonly( &some_class::variable )`` to make a variable readonly and error if someone tries to write to it.
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self call
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---------
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You can pass the 'self' argument through C++ to emulate 'member function' calls in Lua.
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.. code-block:: cpp
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sol::state lua;
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lua.open_libraries(sol::lib::base, sol::lib::package, sol::lib::table);
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// a small script using 'self' syntax
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lua.script(R"(
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some_table = { some_val = 100 }
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function some_table:add_to_some_val(value)
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self.some_val = self.some_val + value
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end
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function print_some_val()
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print("some_table.some_val = " .. some_table.some_val)
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end
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)");
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// do some printing
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lua["print_some_val"]();
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// 100
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sol::table self = lua["some_table"];
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self["add_to_some_val"](self, 10);
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lua["print_some_val"]();
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multiple returns from lua
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-------------------------
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.. code-block:: cpp
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sol::state lua;
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lua.script("function f (a, b, c) return a, b, c end");
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std::tuple<int, int, int> result;
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result = lua["f"](100, 200, 300);
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// result == { 100, 200, 300 }
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int a, int b;
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std::string c;
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sol::tie( a, b, c ) = lua["f"](100, 200, "bark");
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// a == 100
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// b == 200
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// c == "bark"
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multiple returns to lua
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-----------------------
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.. code-block:: cpp
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sol::state lua;
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lua["f"] = [](int a, int b, sol::object c) {
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// sol::object can be anything here: just pass it through
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return std::make_tuple( a, b, c );
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};
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std::tuple<int, int, int> result = lua["f"](100, 200, 300);
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// result == { 100, 200, 300 }
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std::tuple<int, int, std::string> result2;
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result2 = lua["f"](100, 200, "BARK BARK BARK!")
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// result2 == { 100, 200, "BARK BARK BARK!" }
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int a, int b;
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std::string c;
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sol::tie( a, b, c ) = lua["f"](100, 200, "bark");
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// a == 100
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// b == 200
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// c == "bark"
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C++ classes from C++
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--------------------
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Everything that is not a:
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* primitive type: ``bool``, ``char/short/int/long/long long``, ``float/double``
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* string type: ``std::string``, ``const char*``
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* function type: function pointers, ``lua_CFunction``, ``std::function``, :doc:`sol::function/sol::protected_function<../api/function>`, :doc:`sol::coroutine<../api/coroutine>`, member variable, member function
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* designated sol type: :doc:`sol::table<../api/table>`, :doc:`sol::thread<../api/thread>`, :doc:`sol::error<../api/error>`, :doc:`sol::object<../api/object>`
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* transparent argument type: :doc:`sol::variadic_arg<../api/variadic_args>`, :doc:`sol::this_state<../api/this_state>`
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* usertype<T> class: :doc:`sol::usertype<../api/usertype>`
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Is set as a :doc:`userdata + usertype<../api/usertype>`.
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.. code-block:: cpp
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struct Doge {
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int tailwag = 50;
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}
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Doge dog{};
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// Copy into lua: destroyed by Lua VM during garbage collection
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lua["dog"] = dog;
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// OR: move semantics - will call move constructor if present instead
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// Again, owned by Lua
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lua["dog"] = std::move( dog );
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lua["dog"] = Doge{};
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lua["dog"] = std::make_unique<Doge>();
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lua["dog"] = std::make_shared<Doge>();
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// Identical to above
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Doge dog2{};
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lua.set("dog", dog2);
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lua.set("dog", std::move(dog2));
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lua.set("dog", Doge{});
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lua.set("dog", std::unique_ptr<Doge>(new Doge()));
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lua.set("dog", std::shared_ptr<Doge>(new Doge()));
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``std::unique_ptr``/``std::shared_ptr``'s reference counts / deleters will :doc:`be respected<../api/unique_usertype_traits>`. If you want it to refer to something, whose memory you know won't die in C++, do the following:
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.. code-block:: cpp
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struct Doge {
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int tailwag = 50;
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}
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sol::state lua;
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lua.open_libraries(sol::lib::base);
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Doge dog{}; // Kept alive somehow
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// Later...
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// The following stores a reference, and does not copy/move
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// lifetime is same as dog in C++
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// (access after it is destroyed is bad)
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lua["dog"] = &dog;
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// Same as above: respects std::reference_wrapper
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lua["dog"] = std::ref(dog);
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// These two are identical to above
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lua.set( "dog", &dog );
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lua.set( "dog", std::ref( dog ) );
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Get userdata in the same way as everything else:
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.. code-block:: cpp
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struct Doge {
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int tailwag = 50;
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}
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sol::state lua;
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lua.open_libraries(sol::lib::base);
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Doge& dog = lua["dog"]; // References Lua memory
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Doge* dog_pointer = lua["dog"]; // References Lua memory
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Doge dog_copy = lua["dog"]; // Copies, will not affect lua
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Note that you can change the data of usertype variables and it will affect things in lua if you get a pointer or a reference from Sol:
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.. code-block:: cpp
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struct Doge {
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int tailwag = 50;
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}
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sol::state lua;
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lua.open_libraries(sol::lib::base);
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Doge& dog = lua["dog"]; // References Lua memory
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Doge* dog_pointer = lua["dog"]; // References Lua memory
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Doge dog_copy = lua["dog"]; // Copies, will not affect lua
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dog_copy.tailwag = 525;
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// Still 50
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lua.script("assert(dog.tailwag == 50)");
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dog.tailwag = 100;
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// Now 100
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lua.script("assert(dog.tailwag == 100)");
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C++ classes put into Lua
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------------------------
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See this :doc:`section here<cxx-in-lua>`.
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namespacing
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-----------
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You can emulate namespacing by having a table and giving it the namespace names you want before registering enums or usertypes:
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.. code-block:: cpp
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struct my_class {
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int b = 24;
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int f () const {
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return 24;
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}
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void g () {
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++b;
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}
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};
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sol::state lua;
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lua.open_libraries();
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// set up table
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sol::table bark = lua.create_named_table("bark");
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bark.new_usertype<my_class>( "my_class",
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"f", &my_class::f,
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"g", &my_class::g
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); // the usual
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// 'bark' namespace
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lua.script("obj = bark.my_class.new()" );
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lua.script("obj:g()");
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my_class& obj = lua["obj"];
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// obj.b == 25
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This technique can be used to register namespace-like functions and classes. It can be as deep as you want. Just make a table and name it appropriately, in either Lua script or using the equivalent Sol code. As long as the table FIRST exists (e.g., make it using a script or with one of Sol's methods or whatever you like), you can put anything you want specifically into that table using :doc:`sol::table's<../api/table>` abstractions.
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|
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advanced
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--------
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Some more advanced things you can do/read about:
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* :doc:`metatable manipulations<../api/metatable_key>` allow a user to change how indexing, function calls, and other things work on a single type.
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|
* :doc:`ownership semantics<ownership>` are described for how lua deals with (raw) pointers.
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|
* :doc:`stack manipulation<../api/stack>` to safely play with the stack. You can also define customization points for ``stack::get``/``stack::check``/``stack::push`` for your type.
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* :doc:`make_reference/make_object convenience function<../api/make_reference>` to get the same benefits and conveniences as the low-level stack API but put into objects you can specify.
|
|
* :doc:`stack references<../api/stack_reference>` to have zero-overhead Sol abstractions while not copying to the Lua registry.
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* :doc:`unique usertype traits<../api/unique_usertype_traits>` allows you to specialize handle/RAII types from other frameworks, like boost, and Unreal, to work with Sol.
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* :doc:`variadic arguments<../api/variadic_args>` in functions with ``sol::variadic_args``.
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* :doc:`this_state<../api/this_state>` to get the current ``lua_State*``.
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* :doc:`resolve<../api/resolve>` overloads in case you have overloaded functions; a cleaner casting utility.
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