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iOS Objective-C Basics (Retired) Introduction to Objective-C Inheritance

Matt Kalebic
Matt Kalebic
1,247 Points
Posted by Matt Kalebic
Matt Kalebic
1,247 Points

Why do we need to refer to a pointer and class "Ruby *ruby", unlike Circle's "float radius"?

Whereas in Circle we defined a property as: @interface Circle : Shape @property(nonatomic) float radius; @end

Here we define it as: @interface Bling : NSObject @property(nonatomic, strong) Ruby *ruby; @end

Why do we use a class (Ruby) instead of a type (float), and why are we referring to a pointer? I feel like I'm not quite understanding properties despite watching the video - it's taking a while to get used to Obj-C! If I understand a property correctly, it's a way to describe characteristics of an object (radius of a circle, color of a dog, etc.) so I'm not sure how "Ruby *ruby" makes sense.

Thank you!

Matt

1 Answer

Ricardo Hill-Henry
Ricardo Hill-Henry
38,442 Points
Ricardo Hill-Henry
Ricardo Hill-Henry
38,442 Points

A pointer points to an object on the heap. In the case of float, it is a primitive type, and in this case not on the heap; so a pointer is not needed to reference it because the object housing it owns the value. The property declaration does not decide whether or not you use a pointer or not. A property is just a shortcut to creating your method in the .h and .m file and it also creates instance variables for those methods. When creating a property for *ruby, you will get a getter and setter methods getRuby and ruby (the getter), but also an instance variable _ruby. Basically, it saves you time on typing the methods getRuby and setRuby, and making the implementations for them. Ruby *ruby makes sense because in Objective-C, Bling cannot own Ruby. Bling can only point to the location in memory when Ruby exists, and grab the information it needs from there.