Use of alloc init instead of new (Objective-C)

Question

Learning Objective-C and reading sample code, I notice that objects are usually created using this method:

SomeObject *myObject = [[SomeObject alloc] init];

instead of:

SomeObject *myObject = [SomeObject new];

Is there a reason for this, as I have read that they are equivalent?

Answer 1

There are a bunch of reasons here: http://macresearch.org/difference-between-alloc-init-and-new

Some selected ones are:

• new doesn't support custom initializers (like initWithString)
• alloc-init is more explicit than new

General opinion seems to be that you should use whatever you're comfortable with.

Answer 2

Frequently, you are going to need to pass arguments to init and so you will be using a different method, such as [[SomeObject alloc] initWithString: @"Foo"]. If you're used to writing this, you get in the habit of doing it this way and so [[SomeObject alloc] init] may come more naturally that [SomeObject new].

Answer 3

+new is equivalent to +alloc/-init in Apple's NSObject implementation. It is highly unlikely that this will ever change, but depending on your paranoia level, Apple's documentation for +new appears to allow for a change of implementation (and breaking the equivalency) in the future. For this reason, because "explicit is better than implicit" and for historical continuity, the Objective-C community generally avoids +new. You can, however, usually spot the recent Java comers to Objective-C by their dogged use of +new.