CODEWITHSUNDEEP
c++stringfunctionif-statement
user2815333
user2815333

Reputation: 496

How to assign a string to a function C++

So working with a bunch of if statements, I'm thinking someone can help me out with a better way.

Here is what I'm trying to do. Say I have 3 strings, I want to assign that string a function if that string is found...

Currently a basic example of what I'm doing:

if(findStr(string1)) {
    function1(perams);
}
else if (findStr(string2)) {
    function2(perams);
}
else if (findStr(string3)) {
    function3(perams);
}

I am doing something similar on a larger scale, 10 different strings and each string corresponds to it's own function.

I am open to options that involve maybe a structure for my strings?

I would like to just do one if statement, even if a loop is involved. I don't want to have to call "function1", "function2", "function3" I want it to somehow be associated with the string.

Is this possible to do cleanly? or are the if statements the cleanest way to do this?

Thanks guys

Upvotes: 0

Views: 231

Answers (4)

4pie0
4pie0

Reputation: 29764

You can use a map of strings associated with pointers to function, i.e:

In case of class members:

    typedef void (MyClass::*f)( peramsType);
    typedef map< std::string, f> MyMap;

usage 

MyClass t;
f f_ptr = myMap["string1"];
( t.*f_ptr)( perams); // -> call function pointed by f_ptr through t object

In case of non-class members:

    typedef void (*f)( peramsType);
    typedef map< std::string, f> MyMap;

usage:

f f_ptr = myMap["string1"];
( *f_ptr)( perams); // -> call non-class function pointed by f_ptr

Good practice is to derive from std::function, so you can write it like:

#include <functional>

typedef std::function< void( peramsType)> f;
std::map < std::string, f> MyMap;

Upvotes: 6

Danvil
Danvil

Reputation: 23041

In C++11 you can do this:

#include <functional>
#include <map>
#include <string>

typedef std::function<void(PARAMS)> func_t;
typedef std::map<std::string,func_t> map_t;

where PARAMS is a list of your function parameters. For example std::function<void(int,float)> would indicate a function which takes two parameters, an int and a float.

See here for more information about std::function.

Upvotes: 1

jrok
jrok

Reputation: 55425

You can map the strings to functions pointers, check if the string is in the map and then call it. Something like this:

typedef void(*Func)();

void foo1();
void foo2();
void foo3();

std::map<std::string, Func> m =
    { {"first", foo1}, {"second", foo2}, {"third", foo3} };

std::string str = "first";
auto it = m.find(str);
if (it != m.end()) (it->second)();

Upvotes: 1

nullptr
nullptr

Reputation: 11058

You might want to use an array of pairs (string, function pointer), something like:

struct {
  string s;
  void (*f)(Params p);
} my_map[] = { { string1, function1}, {string2, function2} };

for (int i = 0; i < 2; i++) {
  if (findStr(my_map[i].s)) {
    my_map[i].f(perams);
    break;
  }
}

Upvotes: 1

Related Questions