CODEWITHSUNDEEP
iphone
iOS_Passion
iOS_Passion

Reputation: 788

Declare iVar using blocks in objective c

I am new to blocks. I want to create a iVar NSMutableArray which I can access inside a block method.Can someone please tell me how to declare it using _block keyword?`

@interface ViewController : UIViewController
{
    __block NSMutableArray *array;
}
@property (nonatomic, weak) NSMutableArray *array;

Upvotes: 3

Views: 783

Answers (2)

Rob Napier
Rob Napier

Reputation: 299265

You should generally not be accessing ivars from within anything but init and dealloc. So there's almost never a reason to access an ivar directly from within a block. Instead, use accessors on the object that owns the ivar (often self).

For multi-threaded blocks this will look something like this:

__weak id weakself = self;
[obj doSomethingWithBlock:^{
   id strongself = weakself;
   strongself.array = nil; // Can't safely read from the array here without more code.
}];

If this is not a multi-threaded operation, then you can just do this:

__weak id weakself = self;
[obj doSomethingWithBlock:^{
   NSLog(@"%@", weakself.array[0]);
}];

If there is no danger of a retain loop (because the block executes immediately on this thread), you can do this even more simply:

[obj doSomethingWithBlock:^{
   NSLog(@"%@", self.array[0]);
}];

Upvotes: 0

Zaphod
Zaphod

Reputation: 7250

You don't need to set the __block in front of your iVar.

According to : http://developer.apple.com/library/ios/#documentation/cocoa/conceptual/Blocks/Articles/bxVariables.html

When a block is copied, it creates strong references to object variables used within the block. If you use a block within the implementation of a method:

  • If you access an instance variable by reference, a strong reference is made to self;
  • If you access an instance variable by value, a strong reference is made to the variable.

Upvotes: 3

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