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compiler forcing self inside static method of a function while using dispatch_sync


compiler forcing self inside static method of a function while using dispatch_sync

By : maria
Date : November 22 2020, 10:38 AM
wish help you to fix your issue The problem is not about dispatch_async, but it's because you are referencing self in a closure.
Whenever self is used in a closure, it is captured as a strong reference. That can potentially cause a strong reference cycle - to prevent that self is captured by mistake, swift requires that self is explicitly used when accessing properties and methods.
code :


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dispatch_sync inside dispatch_sync causes deadlock

dispatch_sync inside dispatch_sync causes deadlock


By : sofi
Date : March 29 2020, 07:55 AM
Does that help The dispatch_sync blocks the current thread until the dispatched code finishes, and if you're dispatching synchronously from a serial queue, you therefore are effectively blocking the queue, too. So if you synchronously dispatch from serial queue to itself, it results in a deadlock.
But to be clear, dispatch_sync blocks the current thread, not the current queue. When dealing with a concurrent queue, a different worker thread will be used for the subsequently dispatched block and no deadlock results.
static method/function make call to non static function inside same class

static method/function make call to non static function inside same class


By : user2367349
Date : March 29 2020, 07:55 AM
this will help Just go get some OOP terminology out of the way first: functions are static and methods are non-static (even though both are defined using the keyword function in PHP). Static class members belong to the class itself and so there is only one global instance of them. Non-static members belong to instances of the class and so each instance has its own copy of these non-static members1.
This means that you need an instance of the class -- called an object -- in order to use a non-static member.
Why does the C# compiler not complain when we use struct function inside the static methods without defining them static

Why does the C# compiler not complain when we use struct function inside the static methods without defining them static


By : 박광춘
Date : March 29 2020, 07:55 AM
will help you If it would have been a class, would it be clearer? Same behaviour.
Firstly, struct cant be static Simple explanation
Forcing the order of execution using dispatch_sync

Forcing the order of execution using dispatch_sync


By : Abhishek Kumar
Date : March 29 2020, 07:55 AM
around this issue It feels like you're trying to take an existing completion-handler based API and shoe-horn it into a serial queue pattern. But serial queues only make sense when the dispatched blocks are, themselves, synchronous. (And don't confuse this with dispatch_sync ... we're talking about whether the task inside the block is asynchronous or not, not how you dispatched it to your queue.) But you're dealing with asynchronous methods being called from other asynchronous methods.
The basic pattern when dealing with methods that take completion handler blocks, is to eliminate the serial queue altogether (no GCD queue is needed or is useful when the tasks are already asynchronous) and just use completion handler blocks in your own methods, and make the last call in the most deeply nested block call your own completion handler.
code :
- (void)foo:(void (^)())completion {
    [fileObj setFileInfo:file completion:^(NSError *error) {
        // do some other stuff
        completion();
    }];
}

- (void)bar:(void (^)())completion {
    [fileObj getFileInfo:fileName completion:^(NSError *error) {
        // do some other stuff
        completion();
    }];
}
[self foo:^{
    [self bar:^{
        // do whatever you want when its all done
    }];
}];
Method initializing an object in a dispatch_sync Block flagged by static analyzer as returning nil

Method initializing an object in a dispatch_sync Block flagged by static analyzer as returning nil


By : sumit batra
Date : March 29 2020, 07:55 AM
Hope that helps The analyzer takes cues from your own code. The fact that your code is checking if uploadTask is nil tells the analyzer (regardless of anything else it might know about the methods you're calling), that it might be nil. There's a chance that it would keep being nil even after attempts exceeds AFMaximumNumberOfAttemptsToRecreateBackgroundSessionUploadTask. Your own code tells it that. And, if so, and assuming that your method is declared to return a non-nil pointer, then you'd be violating your design contract.
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