Effect of 'myObj = [[[[MyClass alloc] init] autorelease] retain];' ?

Question

I've just downloaded the Facebook iOS SDK and I noticed that in the sample code that comes with the SDK whenever it creates an instance of the Facebook class it does it like this:

_facebook = [[[[Facebook alloc] init] autorelease] retain];

where _facebook is a member variable of the calling object (i.e. not a local variable).

Can anyone explain exactly what's the point of autoreleasing and then retaining it?

Answer 1

It effectively does nothing beyond consuming some cycles and memory.

Or, more precisely, in a correctly written application, it does nothing. In an incorrectly written application, it might mask a bug by lengthening the lifespan of the _facebook object. However, it isn't a real fix.

I found a similar line of code in http://github.com/facebook/facebook-ios-sdk/blob/master/sample/DemoApp/Classes/DemoAppViewController.m If that is what you are referring to then, yes, it is nonsense.

Answer 2

As bbum said, this is utter rubbish. I'm surprised code like that calls itself an SDK.

This code is just inefficient and confusing and is no different in final result to allocate/init.

Answer 3

Will get it fixed