[英]In RxCocoa/RxSwift, how to observe BehaviorRelay<[object]> array size changed
I'd like to subscribe to a BehaviorRelay<[object]>, and I'd like to execute some functions whenever we append or remove elements. 我想订阅一个BehaviorRelay <[object]>,并且无论何时添加或删除元素,我都想执行一些功能。
I've used the distinctUntilChange method 我已经使用了distinctUntilChange方法
BehaviorRelay<[object]>.asObservable().distinctUntilChanged{ $0.count != $1.count}.subscribe{....}
But didn't work. 但是没有用。 What should I try?
我该怎么办? Should I try using other Subjects or Relays to achieve this purpose?
我是否应该尝试使用其他主题或中继来实现此目的?
var objects = BehaviorRelay<[Object]>(value: [])
let disposeBag = DisposeBag()
objects.asObservable()
.subscribe(onNext: { (objects) in
//Do something only when appending or removing elements.
}).disposed(by: disposeBag)
//For example
let tempObj = objects.value
tempObj.append(newObj)
objects.accept(tempObj)//this will be called
tempObj.removeAll()
objects.accept(tempObj)//this will be called
tempObj.property = "Change Property"
objects.accept(tempObj)//this will NOT be called
From documentation: 从文档:
- parameter comparer: Equality comparer for computed key values.
参数比较器:计算键值的相等比较器。
I believe you should check the Equality with ==
operator. 我相信您应该使用
==
运算符检查Equality。 So, in your case, try this way: 因此,在您的情况下,请尝试以下方式:
BehaviorRelay<[object]>
.asObservable()
.distinctUntilChanged{ $0.count == $1.count}
.subscribe{....}
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