diff options
| author | Andy <drumsetmonkey@gmail.com> | 2019-08-29 13:07:45 -0400 |
|---|---|---|
| committer | Andy <drumsetmonkey@gmail.com> | 2019-08-29 13:07:45 -0400 |
| commit | 4ac4b280abf2ffa28caa5a532353115a3033444f (patch) | |
| tree | 2a13d658bb454360b2faf401244bb0321d3460d4 /lib/sol2/examples/source/metatable_customization.cpp | |
| parent | e9758416b18b27a65337c28d9641afc0ee89b34b (diff) | |
| parent | 7a46fa2dd3dad3f038bf8e7339bc67abca428ae6 (diff) | |
Started creating scripting library/namespace and added sol2 for interfacing
Diffstat (limited to 'lib/sol2/examples/source/metatable_customization.cpp')
| -rw-r--r-- | lib/sol2/examples/source/metatable_customization.cpp | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/lib/sol2/examples/source/metatable_customization.cpp b/lib/sol2/examples/source/metatable_customization.cpp new file mode 100644 index 0000000..c259598 --- /dev/null +++ b/lib/sol2/examples/source/metatable_customization.cpp @@ -0,0 +1,151 @@ +#define SOL_ALL_SAFETIES_ON 1
+#include <sol/sol.hpp>
+
+#include <iostream>
+
+struct thing {
+ int member_variable = 5;
+
+ double member_function() const {
+ return member_variable / 2.0;
+ }
+};
+
+#define TEMPLATE_AUTO(x) decltype(x), x
+
+// cheap storage: in reality, you'd need to find a
+// better way of handling this.
+// or not! It's up to you.
+static std::unordered_map<sol::string_view, sol::object> thing_function_associations;
+static std::unordered_map<sol::string_view, sol::object> thing_variable_associations;
+
+void register_thing_type(sol::state& lua) {
+ thing_variable_associations.emplace_hint(thing_variable_associations.cend(),
+ "member_variable", sol::object(lua.lua_state(), sol::in_place, &sol::c_call<TEMPLATE_AUTO(&thing::member_variable)>)
+ );
+ thing_function_associations.emplace_hint(thing_function_associations.cend(),
+ "member_function", sol::object(lua.lua_state(), sol::in_place, &sol::c_call<TEMPLATE_AUTO(&thing::member_function)>)
+ );
+
+ struct call_handler {
+ static int lookup_function(lua_State* L) {
+ sol::stack_object source(L, 1);
+ sol::stack_object key(L, 2);
+ if (!source.is<thing>()) {
+ return luaL_error(L, "given an incorrect object for this call");
+ }
+ sol::optional<sol::string_view> maybe_svkey = key.as<sol::optional<sol::string_view>>();
+ if (maybe_svkey) {
+ {
+ // functions are different from variables
+ // functions, when obtain with the syntax
+ // obj.f, obj.f(), and obj:f()
+ // must return the function itself
+ // so we just push it realy into our target
+ auto it = thing_function_associations.find(*maybe_svkey);
+ if (it != thing_function_associations.cend()) {
+ return it->second.push(L);
+ }
+ }
+ {
+ // variables are different than funtions
+ // when someone does `obj.a`, they expect
+ // this __index call (this lookup function) to
+ // return to them the value itself they're seeing
+ // so we call out lua_CFunction that we serialized earlier
+ auto it = thing_variable_associations.find(*maybe_svkey);
+ if (it != thing_variable_associations.cend()) {
+ // note that calls generated by sol3
+ // for member variables expect the stack ordering to be
+ // 2(, 3, ..., n) -- value(s)
+ // 1 -- source
+ // so we destroy the key on the stack
+ sol::stack::remove(L, 2, 1);
+ lua_CFunction cf = it->second.as<lua_CFunction>();
+ return cf(L);
+ }
+ }
+ }
+ return sol::stack::push(L, sol::lua_nil);
+ }
+
+ static int insertion_function(lua_State* L) {
+ sol::stack_object source(L, 1);
+ sol::stack_object key(L, 2);
+ sol::stack_object value(L, 3);
+ if (!source.is<thing>()) {
+ return luaL_error(L, "given an incorrect object for this call");
+ }
+ // write to member variables, etc. etc...
+ sol::optional<sol::string_view> maybe_svkey = key.as<sol::optional<sol::string_view>>();
+ if (maybe_svkey) {
+ {
+ // variables are different than funtions
+ // when someone does `obj.a`, they expect
+ // this __index call (this lookup function) to
+ // return to them the value itself they're seeing
+ // so we call out lua_CFunction that we serialized earlier
+ auto it = thing_variable_associations.find(*maybe_svkey);
+ if (it != thing_variable_associations.cend()) {
+ // note that calls generated by sol3
+ // for member variables expect the stack ordering to be
+ // 2(, 3, ..., n) -- value(s)
+ // 1 -- source
+ // so we remove the key value
+ sol::stack::remove(L, 2, 1);
+ lua_CFunction cf = it->second.as<lua_CFunction>();
+ return cf(L);
+ }
+ else {
+ // write to member variable, maybe override function
+ // if your class allows for it?
+ (void)value;
+ }
+ }
+ // exercise for reader:
+ // how do you override functions on the metatable with
+ // proper syntax, but error when the type is
+ // an "instance" object?
+ }
+ return 0;
+ }
+ };
+
+ lua.new_usertype<thing>("thing");
+ sol::table metatable = lua["thing"];
+
+ metatable[sol::meta_method::index] = &call_handler::lookup_function;
+ metatable[sol::meta_method::new_index] = &call_handler::insertion_function;
+}
+
+void unregister_thing_type(sol::state&) {
+ thing_function_associations.clear();
+ thing_variable_associations.clear();
+}
+
+int main() {
+
+ std::cout << "=== metatable with custom-built (static) handling ===" << std::endl;
+
+
+ sol::state lua;
+ lua.open_libraries(sol::lib::base);
+
+ // register custom type + storage
+ register_thing_type(lua);
+
+ lua.script(R"(t = thing.new()
+ print(t.member_variable)
+ print(t:member_function())
+ t.member_variable = 24
+ print(t.member_variable)
+ print(t:member_function())
+ )");
+
+ // clear storage
+ unregister_thing_type(lua);
+
+ std::cout << std::endl;
+
+ return 0;
+}
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