Sharing code between Objective-C classes, like Traits in PHP

Question

How can I share code between classes in Objective-C, the way Traits in PHP work?

I thought of using categories, but I wondered if there is something more suitable when it wouldn't be sensible to use inheritance.

Answer 1

There are several ways to share code between classes and each one has its own importance, depending upon the situation:

1. You can use inheritance.

2. You can declare Global Methods.

3. You can put the sharable code in AppDelegate.

4. You can use Singleton Class and put the common code in that class. (Not preferred for sharing code but we can still do it.)

All methods have their own pros/cons. You need to study their applications and use. Hope it helps.

Answer 2

Depends. You should ask yourself why do you want to have the same behaviour in various classes. You can use: Inheritance or design patterns (e.g. Composite pattern).

See: Does Objective-C support traits/mixins?

Answer 3

Not sure if this is the best practice, or what you mean by "sharing code" but I usually have a static class which can hold global values.

The class is static and you can access it from anywhere like this:

[dataModel getMyValue];
[dataModel setMyValue];

It only becomes an issues if you try to write to it from multiple threads, but other than that its a good way to store shared data in your app.

Answer 4

Sharing code in Objective-C can be done only via subclassing or doing composition.

There is no equivalent of PHP's traits here. Categories work in a little bit different way. They're are assigned to a certain class, so you can't use code from category in any class. Unless you create NSObject category, which is good idea only in rare cases. You can treat category as a class extension.

It's possible 'share' interfaces having many different protocols. But it's not exactly what you need, I guess.