如果我在块内使用ivar，这是一个保留周期吗？

Question

I have some idea about retain cycle. If I use self.variable inside block. It is said that I let the view controller retains the block and the block retain the self.property that retain to self. So the retain cycle occurs.However ,if I declare a instance variable , and I use it inside the block , is it a retain cycle? If YES, how to solve the problem?

The code is :

@interface ViewController (){
    NSString *phone;
}
@end
-(void)example
{

    [self.varble ^block
     {
         phone=@"abc";// a retain cycle?
     }];

}

Answer 1

Yes that will still retain self

You should either reference the ivar through a weak instance:

@interface ViewController (){
    NSString *phone;
}
@end
-(void)example
{
    __weak typeof(self) weakSelf = self;
    [self.varble ^block
     {
         typeof(self) self = weakSelf;
         self->phone=@"abc";// a retain cycle?
     }];

}

Or if you weren't changing the value (just simply using it), copy the value of the ivar into a local variable:

@interface ViewController (){
    NSString *phone;
}
@end
-(void)example
{
    NSString *phoneValue = [phone copy]; // the copy is optional, but good practice
    [self.varble ^block
     {
         [phoneValue someMethod];
     }];

}