CODEWITHSUNDEEP
c++qtfunction
Adam
Adam

Reputation: 115

How to execute a function from another function?

I have this code:

#ifndef FUNCSTARTER_H
#define FUNCSTARTER_H

#endif // FUNCSTARTER_H

#include <QObject>

class FunctionStarter : public QObject
{
    Q_OBJECT
public:
    FunctionStarter() {}
    virtual ~FunctionStarter() {}

public slots:
    void FuncStart(start) {
        Start the function
    }
};

In the FuncStart function, you would put your function in as a parameter and then it would execute the parameter (aka the function). How would I do this?

Upvotes: 2

Views: 135

Answers (2)

Stefano Borini
Stefano Borini

Reputation: 143795

either you pass a function pointer, or you define a functor class. A functor class is a class that overloads operator(). This way, the class instance becomes callable as a function.

#include <iostream>

using namespace std;

class Functor {
public:
    void operator()(void) {
        cout << "functor called" << endl;
    }   
};


class Executor {
    public:
    void execute(Functor functor) {
        functor();
    };  
};


int main() {
    Functor f;
    Executor e;

    e.execute(f);
}

Upvotes: 3

Luchian Grigore
Luchian Grigore

Reputation: 258608

You'd pass the function pointer as parameter. This is called a callback.

typedef void(*FunPtr)();  //provide a friendly name for the type

class FunctionStarter : public QObject
{
public:
    void FuncStart(FunPtr) { //takes a function pointer as parameter
        FunPtr();  //invoke the function
    }
};

void foo();

int main()
{
    FunctionStarter fs;
    fs.FuncStart(&foo); //pass the pointer to the function as parameter
                        //in C++, the & is optional, put here for clarity
}

Upvotes: 2

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