Initializing instance object in designated initializer?

Question

I have a Rectangle class which has properties width and height. It also has an instance property/object called origin (-(XYPoint *) origin ). Below is the code for my designated initializer in which I pass the XYPoint object as an argument. Is there a way (or is it okay) if I take the properties of the XYPoint class as arguments in this method and then initialize the XYPoint object as well as allocate memory for it inside the method? Otherwise I have to create an XYPoint object in my main program and pass it as an argument which is a lot more code to type.

-(id) initWithWidth:(int)w andHeight:(int)h andOrigin:(XYPoint *)o
{
    self = [super init];
    if (self) {
        [self setWidth: w andHeight: h];
        self.origin = o;
    }
    return self;
}

P.S.- I am new to programming and Objective C so pardon me if I have stated something technically wrong in my question. Thanks!

The XYPoint class has an instance method setX:(int) x andY: (int) y — Abhishek Khanna, Aug 02 '12 at 23:21

score 0 · Accepted Answer · answered Aug 02 '12 at 23:29

0

Personally--I try to avoid initializers that take parameters. I think it leads to writing lots more code and inflexibility. I use designated initializers for just 2 things:

initializing an object with properties that must not be changed after the object is initialized
initializing an object with properties that are absolutely needed to construct it and cannot be specified later

In general, for Rectangle class, I'd make the use like this:

Rectangle * r = [ [ Rectangle alloc ] init ] ;
r.x = x ;
r.y = y ;
r.origin = o ;

// use r

and not use the designated initializer pattern at all except for the conditions outlined above. (For example, creating immutable Rectangle instances)

Finally, there's probably no need to create a Rectangle class--just use CGRect/NSRect primitive structures.

answered Aug 02 '12 at 23:29

nielsbot

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That means that every time you create a `Rectangle`, you need to repeat the code that would have been in the initializer. Instead of one line, you have four. How would having a `-initWithSize:origin:` lead to "writing lots more code"? Seems like it'd lead to writing less overall. – Caleb Sep 24 '12 at 12:29
To me, code like my example is very straightforward. Always using plain `init` when possible avoids the additional complexity and inflexibility of designated initializers. I.e. let's decide `Rectangle` should have a backgroundColor property... Do I add `initWithSize:origin:backgroundColor:`? Or does the initializer just cover `origin` and `size` with `backgroundColor` set later? Or do I have 3 initializers for the different permutations? etc etc. Using `init` avoids all these questions. – nielsbot Sep 24 '12 at 20:10
To me, designated initializers are special cases of the general rule "`init` your objects". Special cases = complexity. – nielsbot Sep 24 '12 at 20:13

Initializing instance object in designated initializer?

1 Answers1