CODEWITHSUNDEEP
iosswiftuikitrx-swift
Choijun0
Choijun0

Reputation: 41

How Driver in RxSwift doe't make circular reference

I'm student studying ios developer

I wonder how Driver doen't make circular reference?

below two codes show different result


// viewController deinit 
publishRelay
    .asDriver(onErrorJustReturn: "")
    .drive(self.publishRelay2)
    .disposed(by: disposeBag)

// viewContoller doen't deinit
publishRelay
    .subscribe(onNext: { [self] _ in
        
        self.publishRelay2.onNext("")
    })
    .disposed(by: disposeBag)

I watched drive code but there is node code to refer self as weak reference.

below is drive method, strong reference occur

drvie

please help me solve this problem thanks

Upvotes: 1

Views: 49

Answers (1)

Sweeper
Sweeper

Reputation: 275015

You are correct that drive does not create a weak reference from the subscription to self (the view controller). In fact, it does not create any references to self at all. That is why there is no retain cycle.

.drive(self.publishRelay2) does not pass self to drive. It only passes publishRelay2 to drive. self here is merely qualifying publishRelay2, to say "I mean the publishRelay2 property of self, not some other property called publishRelay2". If there are no name conflicts, this self would be redundant.

The subscription would have a strong reference to publishRelay2. This can be seen in the implementation of drive, as the closure passed to subscribe captures observers. But this on its own does not create a retain cycle, since there are no strong references from publishRelay2 to self.

In the .subscribe(onNext: { [self] _ in ... } case on the other hand, you are passing a closure that strongly captures self. The subscription will have a strong reference to the closure, and the closure has a strong reference to self.

If the closure had only captured publishRelay2 instead, there will also be no retain cycles:

.subscribe(onNext: { [publishRelay2] _ in 
    publishRelay2.onNext("")
}
// or if there is a name conflict and "self." is not redundant:
.subscribe(onNext: { [relay = self.publishRelay2] _ in 
    relay.onNext("")
}

Upvotes: 2

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