Pairs & Constructors

Code:

class MyClass{
	public:
		MyClass(int MyInt,char MyChar){i=MyInt;c=MyChar;}
		~MyClass(){};
	private:
		int i;
		char c;
};

MyClass doesn't have an explicit default constructor. Say I want to create a pair of MyClasses, e.g. pair<MyClass,MyClass> tmp;, I (understandably) get the message,

Code:

error: no matching function for call to 'MyClass::MyClass()'

However, I cannot figure out how to call my constructor – if indeed I can in such a situation. Do I have to create a default constructor and initialise the values later? Or alternatively, create instances of MyClass that I bind together in a pair? e.g.

Code:

MyClass t1(1,'a'),t2(1,'a');
pair<MyClass,MyClass>tmp(t1,t2);

I guess my real question is: Is there no way of calling a constructor with arguments when using pair?

You might be able to use:

Code:

std::make_pair(MyClass(1, 'a'), MyClass(1, 'a'));

But in your case perhaps this would suffice:

Code:

std::pair<MyClass, MyClass> tmp(MyClass(1, 'a'), MyClass(1, 'a'));

The latter is exactly what I wanted. Thanks, laserlight!

Originally Posted by Nereus

I guess my real question is: Is there no way of calling a constructor with arguments when using pair?

You could make your constructor (the one with arguments) accept default values for those arguments, the constructor will then work as a default constructor:

Code:

class MyClass{
    public:
        MyClass(int MyInt = 1,char MyChar = 'a'){i=MyInt;c=MyChar;}
        ~MyClass(){};
    private:
        int i;
        char c;
};