使用许多嵌套的switchMap是不好的做法吗? [英] Is it bad practice to use many nested switchMap?

问题描述

我有http拦截器.在该拦截器中，更改请求之前，我需要先打开加载程序.
让我真正担心的是，我最终有很多切换图.

I have http interceptor. In that interceptor, before I change the request, I need a loader to turn on.
What really worries me is that I end up having lots of switchmaps.

为什么?

1. 加载程序是异步的
2. 我还需要将从拦截器传递的消息转换为加载程序服务.翻译消息也是异步的.在拦截器中，我应该在加载程序和翻译完成后运行请求

我在加载程序服务中做什么

showLoader(message){
    return this.translateService.get(message).pipe(switchMap( (translatedMessage)=>{
            this.loader$ = from(this.loadingController.create({message: translatedMessage}));
            return this.loader$.pipe(switchMap((loader)=>{
              return from(loader.present());
            }));
          }));
    }

在我的拦截器中

intercept(request: HttpRequest<any>, next: HttpHandler) {
        return this.loaderService.showLoader("WAITING").pipe(
            take(1),
            switchMap( ()=>{

所以已经嵌套了3个switchmap.在它下面，我需要2到3个以上的切换图(一个用于从存储中获取令牌，另一个用于其他操作).基本上以5个switchmap结束.

so there are already 3 switchmaps nested. and below it, i need 2 or 3 more switchmaps (one for getting tokens from storage and one for something else). basically end up with having 5 switchmaps.

问题:嵌套所有这些switchMap是不好的做法吗?

推荐答案

使用许多switchMap很好，尤其是当您需要异步行为时，不良的做法是接触数据流之外的内容.

It's fine to use many switchMap especially when you need asynchronous behaviour, the bad practice is to touch things outside of the data stream.

在您的代码中，this.loader$是它的一个示例，与其在流之外使用变量，不如尝试构建一个在内部执行您想要的所有事情的管道.

In your code this.loader$ is an example of it, instead of using variables outside of a stream try to build a pipe that does everything you want inside of itself.

如果this.loadingController.create和loader.present与Promise类似，甚至switchMap支持Observable，Promise，Array和Iterator，您甚至可以省略from.

You can even omit from if this.loadingController.create and loader.present are Promise like, switchMap supports Observable, Promise, Array and Iterator.

您的代码可能就是这样

    public showLoader(message) {
        return this.translateService.get(message).pipe(
            switchMap(translatedMessage => this.loadingController.create({message: translatedMessage})),
            switchMap(loader => loader.present()),
        );
    }

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