CODEWITHSUNDEEP
c++constructor
YohjiNakamoto
YohjiNakamoto

Reputation: 393

C++ : constructor setting wrong values

I have this weird problem where the values are well-put in the constructor, but this one doesn't return the right object, it just returns an object with wrongly set values (the default one, I suppose)

Take a look at this screen:

enter image description here

I am sure that the data is right when I debug and enter into the constructor. Here is for example the constructor of UserDetails:

UserDetails::UserDetails( QString _maxDataRate, Request _request ){

unsigned int intMaxDataRate = _maxDataRate.toUInt();
UserDetails(intMaxDataRate, _request);
}

UserDetails::UserDetails( unsigned int _maxDataRate, Request _request ) :
 maxDataRate( _maxDataRate ), request( _request ) {
 this->userID = IDGenerator++;
}

I know this must be a classic C++ error, like a reference problem or something like that, but I don't remember what this could be.

Upvotes: 1

Views: 512

Answers (2)

m.s.
m.s.

Reputation: 16324

You are calling the constructor from within the constructor, i.e. you are creating a temporary object which is destroyed immediately.

You need to do the following:

UserDetails::UserDetails( QString _maxDataRate, Request _request ) 
: UserDetails(_maxDataRate.toUInt(), _request);
{
}

Upvotes: 3

molbdnilo
molbdnilo

Reputation: 66371

You can't call a constructor from another - the line

 UserDetails(intMaxDataRate, _request);

creates a different, unnamed, instance of UserDetails which is destroyed immediately.

In C++11, you can forward the constructor to another:

UserDetails::UserDetails(QString _maxDataRate, Request _request) 
    : UserDetails(_maxDataRate.toUInt(), _request);
{
}

in C++03 and earlier, you'll need to either duplicate the constructor code or use a separate function that you call from both.

Side note: in this case, I believe that you shouldn't have a constructor that accepts a string at all, but perform the conversion (and validate it) outside the class.

Upvotes: 1

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