行为主题退订重构

Question

这不是取消行为主题的唯一方法：

  maxSub;
  fromSub;
  toSub;
  pageNumberSub;
  originalMaxSub;
  selectionSub;
  selectionOfInterestSub;

  constructor(private store: StoreService) {}

  ngAfterContentChecked(){
    this.maxSub = this.store.max$.subscribe((max) => {
      if(max !== null && max !== undefined){
        this.max = max;
        this.maxPages = Math.floor(this.max / Variables.to);
        this.pages = Array.from(Array(this.maxPages), (x, i) => i + 1);
      }
    }, (error) => console.log(error), () => {});

    this.fromSub = this.store.from$.subscribe((from) => {
      if(from !== null && from !== undefined) {this.from = from; this.split = this.to - (this.from - 1)}
    }, (error) => console.log(error), () => {});

    this.toSub = this.store.to$.subscribe((to) => {
      if(to !== null && to !== undefined) {this.to = to; this.split = this.to - (this.from - 1)}
    }, (error) => console.log(error), () => {});

    this.pageNumberSub = this.store.pageNumber$.subscribe((pageNumber) => {
      if(pageNumber !== null && pageNumber !== undefined) {this.page = pageNumber;}
    }, (error) => console.log(error), () => {});

    this.originalMaxSub = this.store.originalMax$.subscribe((originalMax) => {
      if(originalMax !== null && originalMax !== undefined) {this.originalMax = originalMax;}
    }, (error) => console.log(error), () => {});

    this.selectionSub = this.store.selection$.subscribe((selection) => {
      if(selection !== null && selection !== undefined) this.selectedAmount = selection.length;
    }, (error) => console.log(error), () => {});

    this.selectionOfInterestSub = this.store.selectionOfInterest$.subscribe((selectionOfInterest) => {
      if(selectionOfInterest !== null && selectionOfInterest !== undefined) this.selectionOfInterest = selectionOfInterest;
    }, (error) => console.log(error), () => {});
  }

  ngOnDestroy(){
    this.maxSub.unsubscribe();
    this.fromSub.unsubscribe();
    this.toSub.unsubscribe();
    this.pageNumberSub.unsubscribe();
    this.originalMaxSub.unsubscribe();
    this.selectionSub.unsubscribe();
    this.selectionOfInterestSub.unsubscribe();
  }

在常规的旧 Observable 中，您可以：

alive = true;

constructor(private store: StoreService) {}

  ngAfterContentChecked(){
     this.store.thing.subscribe().takeWhile(this.alive)...
  }

  ngOnDestroy(){
    this.alive = false;
  }

这样就简单多了。

有没有办法对行为主体做同样的事情？

另一件事：我是否遗漏了一个基本的属性行为主题，无论订阅被调用多少次，他们只在 class 中订阅一次，这就是为什么没有这样的东西takeWhile() 关于行为主题？

Answer 1

1 - 实际上，您所说的更简单的方法根本不会取消订阅，它只是停止阅读来自可观察对象的内容。所以要么使用退订要么完成。

2 - 由于您同时取消订阅，并且您显然不会将 Subject 用于任何其他用途，因此可以为所有订阅使用相同的 Subject 变量，然后您可以使用一行代码取消订阅而且您不需要初始化所有这些 Subject 实例。

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