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iOS

Posted by fmquaglia
fmquaglia
11,060 Points

dot notation vs method call

Hello TreeHouse fellows,

In Building a Blog Reader Application, in the chapter Passing Data To The Detail View our instructor Amit taught us that (and I quote his words):

In case you are wondering why this is specified like a method,
and not using dot notation as we had seen previously,
you can interchange between dot notation and a method.
As per standard convention, if the property is read only
--which means you cannot write another value to it--
you should preferably call it as a method.

Please indulge my curiosity (I come from Java and Ruby land where dot notation is a de facto language construction).

Is there a technical reason to prefer the dot notation when a property is not read only?

Thanks!

3 Answers

John W
John W
21,558 Points

On dot notation: Dot notation in Objective-C is actually a relatively new thing and is very different from Java's dot notation. It is strictly a shorthand notation for calling the setter and getter methods, equivalent to Java's anObject.setVar(value) and anObject.getVar(). They are not direct access to variables. That's because ALL variables in Objective-C are private. Dot notations simply get converted to the respective method calls for you. Hence, when you have

label.text = @"Hi";

You are really saying [label setText:@"Hi"]. And if you are using the dot notation on the right hand side:

whatsInTheLabel = label.text;

You are really saying whatsInTheLabel = [label getText] (In Objective-C, the getter would simply be [label text], but I gave you getText since you came from a Java background)

For readonly properties, only the getter, i.e. [label getText] is synthesized for you, so you can't use the dot notation on the left hand side as it will try to call the setter (i.e. [label setText:], which doesn't exist) for you.

For readwrite properties, both setter and getter are synthesized.

John W
John W
21,558 Points
John W
John W
21,558 Points

Absolutely! some might disagree though, since the @property directive does provide automatic setter/getter synthesis so you don't have to code up something like -(id)getSomething{ return _something; } for every variable like we did in Objective-C 1.0

Like in Java, you are always welcomed to override these methods and add codes so they get called when the variables are accessed. But the bottom-line is, now with 1 line of property declaration, you get the basic setter/getter for free.

fmquaglia
fmquaglia
11,060 Points

Sweet!

Thanks John W !

fmquaglia
fmquaglia
11,060 Points
fmquaglia
fmquaglia
11,060 Points

Thanks for the clarification, John. Would be fair to say that in this case the dot notation is syntactic sugar only?