CODEWITHSUNDEEP
iphoneiosipadblock
Duck
Duck

Reputation: 35953

iOS Blocks - use of undeclared identifier self

I am new to blocks. I am inside a singleton and I do this

void (^ myBlock)() = ^(){ [self doStuff]; };

I receive this error use of undeclared identifier self.

doStuff is a method inside the singleton.

but if this block is declared inside another method, Xcode is OK.

Why is that? thanks.

Upvotes: 3

Views: 4204

Answers (3)

yinkou
yinkou

Reputation: 5766

You shouldn't call self directly in a block.
Rather you should make a safe block-pointer from self and access it inside your block.

__block id safeBlockSelf = self;
void (^ myBlock)() = ^(){ [safeBlockSelf doSomething]; };

See How do I avoid capturing self in blocks when implementing an API? for more details.

Upvotes: 2

Daij-Djan
Daij-Djan

Reputation: 50099

because every method gets passed self as a hidden param. self is a variable like any other and the block can 'see it/capture it' if in the method

if it is not in a method, self is not a variable set anywhere and the block cant 'see it'

Upvotes: 0

g.revolution
g.revolution

Reputation: 12262

you can define the block in your interface and initialize in any of your methods (including initializers ) in your @implementation file like below:

@interface YourClass {
   void (^ myBlock)();
}

@implementation YourClass

  - (void)yourMethod {
    myBlock = ^(){ [self doStuff]; };
  }


@end

Upvotes: 2

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