iPhone memory 管理

Question

I don't understand this exactly.

if I write:

NSNumber *number = [NSNumber initWithInteger: 5];

do I have to release it?

Is this the same as: NSNumber *number= [NSNumber alloc];

?

Answer 1

You wouldn't call NSNumber *number = [NSNumber initWithInteger: 5]; because NSNumber does not respond to + initWithInteger: . You actually need to call both +alloc and -initWithInteger: , like this:

NSNumber *number = [[NSNumber alloc] initWithInteger:5];

Then you will have to release it later; for every alloc call you make, you should also make a call to release.

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Alternatively, you could get an autoreleased NSNumber using the following class method:

NSNumber *number = [NSNumber numberWithInteger:5];

Methods like this return an autoreleased object, which means that you do not need to release it yourself later.

Answer 2

"The general rule of thumb is: If you alloc, copy, or new, memory management's on you."

I'd add retain to this as well.

Answer 3

First of all, there is no class method named " +(id)initWithInteger: " in NSNumber class. That should be " +(id)numberWithInteger: "

You should not release it. Constructors like " [NSNumber numberWith... " are called convenient constructors . They return autoreleased objects . So, you don't have to worry about releasing them.