How does char pointer reference to function name in C++ [duplicate]

Question

I am very kindergartener to C++. Hope someone can help me out with my problem.

Assume there is a function defined in one class.

void __foo__(int x, int y){
      //do something
}

In another class, there is a char pointer that holds the value of the function name.

static const char *func = "__foo__";

How do I call the function by using the "func" like func(0, 0)?

C++ doesn't have reflection, so you have to write the code to call the function based on the name yourself — Mooing Duck
– Mooing Duck, Commented May 21, 2021 at 17:56
On a side note, identifiers containing a double underscore are reserved. — G.M.
– G.M., Commented May 21, 2021 at 17:58
Rather than suggest writing your own reflection code, I'm going to suggest not using strings to call functions in the first place. #include the class and call the function on an instance of it. And underscores like that are reserved. Use snake_case, camelCase or PascalCase (in my decreasing order of preference). — user14217014
– user14217014, Commented May 21, 2021 at 17:59
It's very important to clarify why you're trying to do that. — Aykhan Hagverdili
– Aykhan Hagverdili, Commented May 21, 2021 at 18:09

Aykhan Hagverdili · Accepted Answer · 2021-05-21 18:10:10Z

1

C++ doesn't have reflection, so you have to write the code to call the function based on the name yourself

void fall_function_based_on_name(const char* func_name, classWithMethod* self, lint x, int y) {
    if (strcmp(func_name, "__foo__")==0)
        self->__foo__(x, y);
    else 
        throw std::logic_error("method name not found");
}

edited May 21, 2021 at 18:10

Aykhan Hagverdili

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answered May 21, 2021 at 17:59

Mooing Duck

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3 Comments

user4581301 Over a year ago

Aside: std::map and std::unordered_map can be useful here if you have a medium-large list of named functions or a use case that prizes ease of writing over performance.

user3842642 Over a year ago

Appreciate it so much for the help, @Mooing Duck. I guess the reason why it was given with the char pointer is that the foo__() will be given in the separate file during the runtime. Therefore, by calling _foo__() will produce "_foo was not declared in this scope" error in compile time.

Mooing Duck Over a year ago

@user3842642: Standard C++ doesn't have the concept of functions that don't exist at compile time, but most Operating Systems have ways of loading "dynamic libraries" at runtime (dlls on Windows). That's OS-specific though.

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