Question

In objective-c whats the difference between using a . and using ->? I’ve used dot notation many times but have only just come across ->

E.G

Object.subObject

or

Object->subObject

Answer 1

myObject.myProperty

The dot could either be calling a the getter/setter for a property or accessing a struct.

In your case subObject is probably not a struct so using myObject.myProperty would be the same as calling the method [myObject myProperty] which is the getter for the "myProperty" property.

The same way when you are setting a new value using the dot. You are calling [myObject setMyProperty:newValue]; which will do the appropriate memory management defined for your property (like retain, copy or assign the value as well as release the old value).

(Using getters and setters will also call the work with KVO)

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myObject->myProperty

The arrow is pointing to the memory of the variable.

This simply means that you are following the pointer that points to the memory where myProperty is located. This is lower level and does not do any memory management for you, nor does it work with KVO.