将单个订阅变量与 BehaviorSubject 一起使用 [英] Using a single subscription variable with BehaviorSubject

问题描述

我在我的 Angular 应用程序中使用 BehaviorSubject 并且我可以从 DataService 观察到我的 Details 组件，如图所示下面:

I use BehaviorSubject in my Angular app and I get observable to my Details component from DataService as shown below:

DataService.ts:

export class DataService {

    private messageTracker = new BehaviorSubject<any>();
    private fileTracker = new BehaviorSubject<any>();

    getMessageTracker(): Observable<any> {
        return this.messageTracker.asObservable();
    }

    getFileTracker(): Observable<any> {
        return this.fileTracker.asObservable();
    }

    //set methods omitted for brevity
}

细节组件:

export class DetailComponent implements OnInit {

    subscription; //??? Can I use this variable for every subscription below?

    constructor(private dataService: DataService) { }

    ngOnInit(): void {

        this.subscription = this.dataService.getMessageTracker().subscribe((param: any) => {
                //...  
        });

        this.subscription = this.dataService.getFileTracker().subscribe((param: any) => {
            //...
        });
    }
}

ngOnDestroy(): void {
    this.subscription.unsubscribe();
}

我的问题是:

1) 据我所知，如上所述，我应该为每个事件创建一个新的 BehaviorSubject 变量，例如messageCreateTracker(用于跟踪添加的新消息)，fileCreateTracker(用于跟踪添加的新文件，messageUpdateTracker(用于跟踪更新的消息).都是真的吗?

1) As far as I know, as above, I should create a new BehaviorSubject variable for each event e.g. messageCreateTracker (for tracking a new message added), fileCreateTracker (for tracking a new file added, messageUpdateTracker (for tracking a message updated). Is that all true?

2) 看 DetailComponent，我只为 Observables 的每个订阅使用了一个 subscription 变量.这是一个糟糕的方法吗?我应该为 ngOnInit() 中的每个订阅创建一个新的订阅变量吗?

2) Looking DetailComponent, I just used a single subscription variable for every subscriptions of Observables. Is that a bad approach? Should I create a new subscription variable for each subscriptions in ngOnInit()?

推荐答案

查询 1 的答案:

它取决于开发者的编码风格，或者他的想法，你也可以传递事件和数据的类型，在这种情况下，你只需要一个BehaviorSubject，像这样:

It depends on the developer's coding style, or how he thought, you can also pass the type of event and data with that, in that case, you will need only one BehaviorSubject, like this :

this.messageTracker.next({ type : 'create' ,  data });
this.messageTracker.next({ type : 'update' ,  data });
this.messageTracker.next({ type : 'delete' ,  data });

但是这也会造成复杂性如果它变大，收益取决于项目的要求，你的方式也不错.

But this can also create a complexity if it goes large, gain depends on the requirements of the project, your way is also good.

问题 2 的答案:

基本上，您不能处理多个订阅，因为它会覆盖前一个订阅，并且只会取消订阅最后一个:

Basically, you can't handle multiple subscriptions like that it will override the previous one and it will only unsubscribe the last one :

因此您可以为订阅的或单个数组/对象创建多个变量，然后取消订阅所有:

So you can create multiple variables for that OR single array/object of your subscription and then unsubscribe all :

使用数组:

this.subscription = [];
this.subscription.push(this.dataService.getMessageTracker().subscribe((param: any) => {}));    
this.subscription.push(this.dataService.getFileTracker().subscribe((param: any) => {}));

ngOnDestroy(): void {
    this.subscription.forEach(sub => {
        sub.unsubscribe();
    })
}

带对象:

this.subscription = {};
this.subscription['messageTracker'] = this.dataService.getMessageTracker().subscribe((param: any) => {}));
this.subscription['fileTracker'] = this.dataService.getFileTracker().subscribe((param: any) => {}));

this.subscription['fileTracker'].unsubscribe(); // <--- You can also do
delete this.subscription['fileTracker']; // <--- then dont forgot to remove, or will throw error in ngOnDestroy

ngOnDestroy(): void {
    for(key in this.subscription) {
      this.subscription[key].unsubscribe();
    }
}

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