How Can I Call Functions by Name (Stored in a std::string) in C ?

Calling Functions by Name (std::string) in C

In C , one cannot directly call a function by name stored in a string. However, workarounds exist to achieve this functionality.

Basic Approach

The basic approach involves using a series of "if-else" statements or a "switch-case" construct, explicitly checking for the function name stored in the string and calling the corresponding function. As demonstrated in the provided code snippet, this method requires manually maintaining a list of functions and their names.

Reflection

The approach suggested in the question is referred to as reflection, which involves dynamically accessing and manipulating program elements at runtime. While reflection is not natively supported in C , some libraries provide limited reflection capabilities.

Workaround Using std::map

One workaround involves creating a std::map that associates function names (std::string keys) with function pointers (int (*FnPtr)(int, int) values). This allows for efficient retrieval and invocation of functions based on their names.

The provided code snippet illustrates this approach:

<code class="c++">#include <iostream>
#include <map>

int add(int i, int j) { return i + j; }
int sub(int i, int j) { return i - j; }

typedef int (*FnPtr)(int, int);

int main() {
    std::map<std::string, FnPtr> myMap;
    myMap["add"] = add;
    myMap["sub"] = sub;

    std::string s("add");
    int res = myMap[s](2, 3);
    std::cout << res;
}</code>

In this example, the myMap[s](2, 3) expression retrieves the function pointer associated with the string "add" and invokes it with arguments 2 and 3, resulting in an output of 5.

The above is the detailed content of How Can I Call Functions by Name (Stored in a std::string) in C ?. For more information, please follow other related articles on the PHP Chinese website!