Different ways of initializing objects in Objective-C

Question

There are two ways of initializing objects in Objective-C, i.e.:

1) AVCaptureSession *captureSession = [[AVCaptureSession alloc] init];

2) AVCaptureSession *session = [AVCaptureSession new];

Seems like they are doing the same job. What is the difference between them? Or "new" it is just a novelty of iOS5?

Would be grateful for the answer,

Artem

Tommy · Accepted Answer · 2011-11-04 15:06:18Z

3

new is a shortcut way of doing an alloc/init that should work on any object, but it's mainly a hangover from Smalltalk and new calls never take arguments so you don't see it used much at all any more.

So the two should be identical and it's a novelty but not of iOS 5.

EDIT: further to this, new is defined on NSObject as something that calls alloc and then init and is given as having been available since Mac OS X 10.0 (which is the beginning of time as far as Apple's documentation is concerned).

answered Nov 4, 2011 at 15:06

Tommy

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Joshua Nozzi Over a year ago

Note that many objects have designated initializers other than -init, so it's not appropriate to call -new. A prime example would be creating any type of NSView subclass (including all Cocoa controls) in code. The designated initializer is -initWithFrame: and takes a rectangle as an argument. Initializing a view with -init will give you unpredictable (and usually undesirable) results so you need the alloc/initWithFrame: pair. Lesson: Don't use -new just anywhere. :-)

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