lua_class inherit cpp_class cannot register new function

[longlt3]

cpp:

struct State { };

lua:

state_sleep = State.new()
function state_sleep:execute()
-- do smt
end

above code caused a crash.

does sol2 can do these stuff ?

[ThePhD]

No. sol2 cannot register a new function on an instance. It can only register on a new class. Use State:execute to add to the class.

You can also achieve this functionality by having a table that defers its unknown operations to State's metatable. You can do this by creating a table and then setting its __newindex and __index functions appropriately.

[ThePhD]

Now with a clarification and a reader's note: http://sol2.readthedocs.io/en/latest/api/usertype.html?highlight=usertype#runtime-functions

There's also an example in the repository illustration this concept directly:
https://github.com/ThePhD/sol2/blob/develop/examples/runtime_additions.cpp

[longlt3]

I got it now
Thank you :)

[longlt3]

@ThePhD Could you please make more clear about

You can also achieve this functionality by having a table that defers its unknown operations to State's metatable. You can do this by creating a table and then setting its __newindex and __index functions appropriately.

I tried this way, but no luck
cpp:

    struct Base
    {
        int m_val;
        void base_func() { printf("base_func\n"); }
    };
    sol::state l_sol;
    l_sol.open_libraries( sol::lib::base, sol::lib::ffi, sol::lib::jit, sol::lib::io );

    l_sol.new_usertype<Base>( "Base"
        , "base_func", &Base::base_func
        , "m_val", &Base::m_val
        );

lua:

Derived = {}
Derived.__index = Base.__index
Derived.__newindex = Base.__newindex

function Derived:new (o)
    o = o or {}
    setmetatable(o, self)
    return o
end

function Derived:derived_func()
    print(tostring(self).." Derived:derived_func")
end

local l_ins = Derived:new()
l_ins:derived_func()

-- l_ins:base_func() // crashed
-- print(l_ins.m_val) // crahsed

Thank you very much