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?
- 加载程序是异步的
- 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()),
);
}
这篇关于使用许多嵌套的switchMap是不好的做法吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！