RxJs 唯一地合并两个 observables

Question

我正在使用 rxjs 在 angular 应用程序中构建搜索和过滤系统。

我有以下内容：

interface User{ //exmaple model
 _id: string;
 name: string;
}

filters$ = new BehaviorSubject<Array<User>>([]);
search$ = new BehaviorSubject<Array<User>>([]);

// I use these two and merge them in another function as following

const myData$ = merge(this.search$.asObservable(), this.filters$.asObservable())
.pipe(distinctUntilChanged(distinctCheck))

效用函数 distinctCheck 类似于：

const distinctKey = (elem) => {
    if(elem === null){
      return elem
    }
    if(this.hasId(elem)){
      return elem["_id"];
    }
    if(this.hasName(elem)){
      return elem["name"]
    }
    return this.createComparisonString(elem)
  }

但这使我无法观察到一个或另一个。所以我的问题是：

如何合并两个可观察对象并仅发出两个数组共有的值？有时 filters$ 可能会发出一个包含 30 个元素的数组。有时 search$ 可能会发出只有 2 个元素的数组？

I.E:

如果 filter$ 包含：

[{_id:'1', name:'jhon'},{_id:'2', name:'doe'},{_id:'3', name:'jolly'},{_id:'4', name:'some random dude'},{_id:'5', name:'some random other dude'},{_id:'6', name:'johny'},{_id:'7', name:'bravo'}]

和search$包含：

[{_id:'1', name:'jhon'},{_id:'101', name:'myDoe'},{_id:'301', name:'some-jolly'},{_id:'4', name:'some random dude'}, {_id:'7', name:'bravo'}]

我想 myData$ 发出类似的东西：

[{_id:'1', name:'jhon'},{_id:'4', name:'some random dude'}, {_id:'7', name:'bravo'}]

谢谢大家！ :)

Answer 1

像这样的东西应该可以工作：

const filters$ = new BehaviorSubject<Array<{ id: string }>>([]);
const search$ = new BehaviorSubject<Array<{ id: string }>>([]);

const combinedAndFiltered$ = combineLatest(filters$, search$)
    .pipe(map(([filters, searches]) => {
        return filters.filter(filter => !!searches.find(search => search.id === filter.id));
    }));

combinedAndFiltered$.subscribe(console.log)

Answer 2

distinctUntilChanged运算符的compare函数用于判断上一次发射是否与当前发射不同。

据我了解您的问题，您正在寻找 search 和 filter 数组之间的交集。

首先，使用 combineLatest 运算符在 filter$ 的 search$ 发出时得到通知。
然后，您可以使用类似 lodash 的 intersectionWith 来获取数组交集。

您的代码应如下所示：

const comperator = (search, filter) => filter._id === search._id && filter.name === search.name; 

const myData$ = combineLatest(search$, filter$).pipe(
  map(([search, filter]) => intersectionWith(search, filter, comperator))
);

您可以在 this stackblitz

中查看完整的运行代码

Answer 3

你实际上可以用简单的 Javascript 来实现它。

var filterArr = [{_id:'1', name:'jhon'},{_id:'2', name:'doe'},{_id:'3', name:'jolly'},{_id:'4', name:'some random dude'},{_id:'5', name:'some random other dude'},{_id:'6', name:'johny'},{_id:'7', name:'bravo'}]
var searchArr = [{_id:'1', name:'jhon'},{_id:'101', name:'myDoe'},{_id:'301', name:'some-jolly'},{_id:'4', name:'some random dude'}, {_id:'7', name:'bravo'}]

var data = filterArr.filter(userFilter => searchArr.some(userSearch => userFilter._id == userSearch._id))

console.log(data);

至于可观测值，您可以尝试使用 combineLatest 方法将它们组合起来。

const myData$ = combineLatest(this.search$.asObservable(), this.filters$.asObservable()).pipe(
  map(([filterArr, searcheArr]) => filterArr.filter(userFilter => searchArr.some(userSearch => userFilter._id == userSearch._id)))
)

RxJs 唯一地合并两个 observables

RxJs merging two observables uniquely

rxjs

typescript

angular

rxjs6