在Objective-C中通知自定义委托类

Question

I have successfully set up a delegate in my NSObject class and I'm able to transfer some data and run some selectors.

The thing is, I can't understand how do I send some values back to that class where I've set up my delegate. I have a ViewController, SGDownloader that has a BOOL property and I want to check it on the delegate class to make a conditional firing of some selector. The thing is, I can't seem to make it work. I'm using storyboards and here's my code:

-(void)checkTheQueue {
    SGDownloader *downloaderInstance = [SGDownloader new];
    NSLog((@"Downloader is now %i"), downloaderInstance.isBusy);
    BOOL checkBool = downloaderInstance.isBusy;

    if (checkBool == NO) {
        SEL selector = @selector(checkTheThing);
        if (delegate && [delegate respondsToSelector:selector]) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
            [delegate performSelector:selector];
#pragma clang diagnostic pop
        }
    }
    else {
        NSLog(@"Sorry, I'm busy");
    }
}

I fire the selector checkTheThing in my first class, the class I'd like to get the isBusy value from. It's also an @optional delegate method. The thing is, that the BOOL value is always 0, and if I try to pass a string it's always nil .

I suspect there's a problem with this line - SGDownloader *downloaderInstance = [SGDownloader new]; maybe the storyboard get's mixed up or something like that.

Edit:

Part of the code from SGDownloader :

- (IBAction)attemptNewDownload:(id)sender {

    SGQueueController *myProtocol = [SGQueueController new];
    myProtocol.delegate = self;
    NSLog((@"Busy value equals %i while checking the protocol"), isBusy);
    [myProtocol checkTheQueue];
}

Here NSLog tells me that the value is 1. Seconds later it's 0 on my protocol class. Although nothing is done with it later on.

Answer 1

Your Code should work, but you're looking at the wrong Place.

isBusy gets set in viewDidLoad of SGDownloader, right? In attemptNewDownload you create an Instance of SGQueueController. Then you set its Delegate to the already created SGDownloader and call checkTheQueue on it.

In checkTheQueue you create a new Instance of SGDownloader, but new doesn't call viewDidLoad (by default). So the isBusy -property of the newly created SGDownloader-Instance is still NO. Just let out the [SGDownloader new] -line and change

BOOL checkBool = downloaderInstance.isBusy;

to

BOOL checkBool = delegate.isBusy;