I have a readonly property isFinished in my interface file:

typedef void (^MyFinishedBlock)(BOOL success, NSError *e);

@interface TMSyncBase : NSObject {
     BOOL isFinished_;
}

@property (nonatomic, readonly) BOOL isFinished;

and I want to set it to YES in a block at some point later, without creating a retain cycle to self:

- (void)doSomethingWithFinishedBlock:(MyFinishedBlock)theFinishedBlock {
    __weak MyClass *weakSelf = self;
    MyFinishedBlock finishedBlockWrapper = ^(BOOL success, NSError *e) {
        [weakSelf willChangeValueForKey:@"isFinished"];
        weakSelf -> isFinished_ = YES;
        [weakSelf didChangeValueForKey:@"isFinished"];
        theFinishedBlock(success, e);
    };

    self.finishedBlock = finishedBlockWrapper; // finishedBlock is a class ext. property
}

I'm unsure that this is the right way to do it (I hope I'm not embarrassing myself here ^^). Will this code leak, or break, or is it fine? Perhaps there is an easier way I have overlooked?

SOLUTION

Thanks to the answers below (especially Krzysztof Zablocki), I was shown the way to go here:

Define isFinished as readwrite property in the class extension (somehow I missed that one) so no direct ivar assignment is needed, and change code to:

- (void)doSomethingWithFinishedBlock:(MyFinishedBlock)theFinishedBlock {
    __weak MyClass *weakSelf = self;
    MyFinishedBlock finishedBlockWrapper = ^(BOOL success, NSError *e) {
        MyClass *strongSelf = weakSelf;
        strongSelf.isFinished = YES;
        theFinishedBlock(success, e);
    };
    self.finishedBlock = finishedBlockWrapper; // finishedBlock is a class ext. property
}