我开始使用 ngrx let 来使用普通对象。
问题是,当我在组件中使用大量可观察量时,我最终得到的代码看起来很糟糕(ng-container inside ng-container inside ng-container inside ng-container ...):
<ng-container *ngrxLet="obs1$ as obs1">
<ng-container *ngrxLet="obs2$ as obs2">
<ng-container *ngrxLet="obs3$ as obs3">
<ng-container *ngrxLet="obs4$ as obs4">
<app-comp [data]="obs1" ..>..</app-comp>
<app-comp2 [data]="obs1" [data2]="obs3"..>..</app-comp2>
<app-comp3 [data]="obs1" ..>..</app-comp3>
<app-comp4 [data]="obs1" ..>..</app-comp4>
<app-comp5 [data]="obs4" [data11]="obs1" ..>..</app-comp5>
<app-comp6 [data]="obs2" ..>..</app-comp6>
<app-comp7 [data]="obs3" ..>..</app-comp7>
</app-number>
</ng-container>
有更好的方法来处理这种语法吗?
<ng-container *ngrxLet="{obs1: obs1$, obs2: obs2$, obs3: obs3$} as context">
<app-comp1 [data]="context.obs1" ..>..</app-comp1>
<app-comp2 [data]="context.obs2" ..>..</app-comp2>
<app-comp3 [data]="context.obs3" ..>..</app-comp3>
</ng-container>
ngrxLet 似乎不支持该功能,您可以使用前面答案中提到的combineLatest 或尝试一些我与 *ngIf 一起使用的 trcik
<ng-container *ngIf="{
obs1: obs1$ | async,
obs2: obs2$ | async,
obs3: obs3$ | async,
obs4: obs4$ | async
} as data">
<app-comp [data]="data.obs1"></app-comp>
<app-comp2 [data]="data.obs1" [data2]="data.obs3"></app-comp2>
<app-comp3 [data]="data.obs1"></app-comp3>
<app-comp4 [data]="data.obs1"></app-comp4>
<app-comp5 [data]="data.obs4" [data11]="data.obs1"></app-comp5>
<app-comp6 [data]="data.obs2"></app-comp6>
<app-comp7 [data]="data.obs3"></app-comp7>
</ng-container>
combineLatest
、
zip
和
forkJoin
)组合控制器中的可观察量。每个都有特定的机制,您可以在这里找到它们之间的差异。 插图使用
combineLatest
combined$: Observable<any>;
ngOnInit() {
this.combined$ = combineLatest(
obs1$.pipe(startWith(null)),
obs2$.pipe(startWith(null)),
obs3$.pipe(startWith(null)),
obs4$.pipe(startWith(null))
).map(([obs1, obs2, obs3, obs4]) => ({ // <-- `map` emits a user-friendly object
obs1: obs1,
obs2: obs2,
obs3: obs3,
obs4: obs4
}));
}
模板
<ng-container *ngrxLet="combined$ as data">
<app-comp [data]="data?.obs1" ..>..</app-comp>
<app-comp2 [data]="data?.obs1" [data2]="data?.obs3"..>..</app-comp2>
<app-comp3 [data]="data?.obs1" ..>..</app-comp3>
<app-comp4 [data]="data?.obs1" ..>..</app-comp4>
<app-comp5 [data]="data?.obs4" [data11]="data?.obs1" ..>..</app-comp5>
<app-comp6 [data]="data?.obs2" ..>..</app-comp6>
<app-comp7 [data]="data?.obs3" ..>..</app-comp7>
</ng-container>
但是有一个警告。除非每个可观察源至少发射一次,否则 combineLatest
和
zip
不会开始发射。我们可以使用
startWith
运算符强制执行它,如下所示。但是您需要确保第一个值(此处为
null
)不会影响数据绑定。您当然可以将
*ngrxLet
替换为
*ngIf
以避免发出
null
,但这样您就会失去
*ngrxLet
的好处。