Custom function about my_basic

[paladin-t]

Hi,

It's not able to call a non-static method without an instance in C++, I mean you can't simply do that. But we are still able to do it with some tricks. The problem is C++ needs to know which instance a method will execute with, so we can store an instance and tell C++.

With MY-BASIC, for example, assume we got a C++ class:

class AClass {

public:
    void foo(void) const;

};

Now I'd define some bridge function:

int _a_new_instance(mb_interpreter_t* s, void** l) {
    // Creates an instance of AClass.

    mb_value_t ret;

    ...

    mb_check(mb_attempt_open_bracket(s, l));

    mb_check(mb_attempt_close_bracket(s, l));

    ret.type = MB_DT_USERTYPE;
    ret.value.usertype = (void*)(new AClass);

    ...
}

int _a_foo_bridge(mb_interpreter_t* s, void** l) {
    // Calls the foo method of an AClass instance.

    mb_value_t ret;
    AClass* inst = NULL;

    ...

    mb_check(mb_attempt_open_bracket(s, l));

    mb_check(mb_pop_value(s, l, &a));

    mb_check(mb_attempt_close_bracket(s, l));

    inst = (AClass*)a.value.usertype;
    inst->foo();

    ...
}

Don't forget to register them. Then in MY-BASIC code:

a = a_new_instance()
a_foo_bridge(a) ' Calls the foo method.

This is not the only way to call a non-static C++ method with C, it's just a simple practice. You could find a proper way by searching something like "call c++ method from c". There are also many ways to store a non-static method and its corresponding instance in a variable, you may would like to take a look at "function bind" if you were using C++11, or use the famous very lightweight Fastdelegate lib for C++.

BTW. MB_DT_USERTYPE_REF is more intelligent than MB_DT_USERTYPE, because MY-BASIC can manage the deallocation of a referenced object with Reference Counting and GC.

Best
WRX