Question

self is a hidden instance variable that points to the current object:

- (id) initWithAmount:(double)theAmount forBudget:(Budget *)aBudget{

        if(self = [super init]){

                budget = aBudget;
                amount = theAmount;

        }
        return self;
}

is it similar to

this.budget=super.aBudget;
this.amount=super.theAmount;

Normally:

if(control)//true or false
     {
      //stmts will get executed 
     }

but instead of returning a true value here the self is assigned with super. Why is it so?

Is it similar to constructor. How to use constructors(default,parameterised and copy) in objective C?

Answer 1

This form is just the short form of the following code:

- (id)initWithAmount:(double)theAmount forBudget:(Budget *)aBudget {
  self = [super init]; // you must do this, because every object inherits all properties
                       // from the parent class, and they must be initialized

  // init can return nil if there was an error during the initialization
  // so if the parents initialization failed, there is no point of initializing
  // the child object
  if (self != nil) {
    budget = aBudget;
    amount = theAmount;
  }

  return self;
}