What's the difference between dot syntax and square bracket syntax?

Question

I am going through some walkthroughs fpr Objective-C and I got to many places where I raised my eyebrows. I would love to get them down.

1. Is there a fundamen

Answer 1

It's a distinction oriented at the person reading your code. Dot syntax indicates state (I'm accessing an ivar), method syntax indicates behavior (I'm performing some action). To the runtime, both are the same.

I think Apple's intention is to show accessors as an implementation detail you shouldn't worry about. Even when they could trigger side effects (due to some additional code in the accessor), they usually don't, so the abstraction is imperfect but worth it (IMHO). Another downside of using dot notation is that you don't really know if there is a struct or a union behind it (which unlike message sending, never trigger side effects when being assigned). Maybe Apple should have used something different from a dot. *shrugs*

I think maybe nested messages cannot be created using the dot operator strategy?

Dot notation can be used to nest calls, but consider the following:

shu.phyl.we.spaj.da
[[[[[shu]phyl]we]spaj]da]

In this case, the uglier, the better. Both are a code smell because one object is creating dependencies to another object far far away, but if use brackets to pass messages you get that extra horrible syntax from the second line, which makes the code smell easier to notice. Again, convention is to use dots for properties and brackets for methods.