typescript 将数据添加到行为对象数组 Angular 5 的末尾
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add data to the end of a behavior object array Angular 5
提问by Smokey Dawson
I have some data that I want to be shared with my entire app so I have created a service like so..
我有一些数据想要与我的整个应用程序共享，所以我创建了一个这样的服务..
user.service
用户服务
userDataSource = BehaviorSubject<Array<any>>([]);
userData = this.userDataSource.asObservable();
updateUserData(data) {
this.userDataSource.next(data);
}
then in my component Im getting some data from an api and then sending that data to userDataSourcelike so..
然后在我的组件中，我从 api 获取一些数据，然后将这些数据发送给userDataSource这样..
constructor(
private: userService: UserService,
private: api: Api
){
}
ngOnInit() {
this.api.getData()
.subscribe((data) => {
this.userService.updateUserData(data);
})
}
now that all works but.. I want to be able to add data to the end of the array inside the userDataSourceso basically the equivalent of a .pusham I able to just call the updateUserData()function and add more data or will doing that overwrite what is currently in there?
现在一切正常，但是..我希望能够将数据添加到数组的末尾，userDataSource所以基本上相当于.push我能够调用该updateUserData()函数并添加更多数据，或者这样做会覆盖当前的内容那里？
Any help would be appreciated
任何帮助，将不胜感激
回答by Arun Redhu
You can add a new method to your service like addDatain which you can combine your previous data with new data like.
您可以为您的服务添加一种新方法，例如addData您可以将以前的数据与新数据相结合。
import {Injectable} from '@angular/core';
import {BehaviorSubject} from 'rxjs/BehaviorSubject';
@Injectable()
export class UserService {
userDataSource: BehaviorSubject<Array<any>> = new BehaviorSubject([]);
userData = this.userDataSource.asObservable();
updateUserData(data) {
this.userDataSource.next(data);
}
addData(dataObj) {
const currentValue = this.userDataSource.value;
const updatedValue = [...currentValue, dataObj];
this.userDataSource.next(updatedValue);
}
}
回答by G. Siganos
For someone that may come accross this issue with a BehaviorSubject<YourObject[]>.
对于可能会遇到此问题的人BehaviorSubject<YourObject[]>。
I found in this articlea way to properly add the new array of YourObject
我在这篇文章中找到了一种正确添加新数组的方法YourObject
import { Observable, BehaviorSubject } from 'rxjs';
import { YourObject} from './location';
import { Injectable } from '@angular/core';
@Injectable({
providedIn: 'root'
})
export class ObjService {
private theObjData: BehaviorSubject<YourObject[]> = new BehaviorSubject<YourObject[]>(null);
constructor() {
}
public SetObjData(newValue: YourObject[]): void {
this.theObjData.next(Object.assign([], newValue));
}
}
How to update data:
如何更新数据：
// inside some component
this.api.userData().subscribe((results:YourObject) =>
this.objService.SetObjData(results);
)
How to observe changes on other component
如何观察其他组件的变化
// inside another component
ngOnInit() {
this.objService.GetAccountStatements().subscribe((results) =>
...
)
}
回答by joh04667
Normally Observablesand Subjects are meant to be streamsof data, not an assignment of data. BehaviorSubjects are different because they hold their last emitted value.
通常Observables和Subjects 是数据流，而不是数据分配。BehaviorSubjects 是不同的，因为它们保存着最后发出的值。
Normally Subjects or BehaviorSubjectsinside of a contained class (like a Service) do not want to expose themselves publicly to any other classes, so it's best practice to access their properties with getters or methods. This keeps the data stream cold to all subscribers.
通常Subjects 或BehaviorSubjects包含的类（如服务）不希望将自己公开给任何其他类，因此最佳实践是使用getter 或方法访问它们的属性。这使所有订阅者的数据流保持冷态。
However, since the BehaviorSubjectholds the last emitted value, there's a few options here. If allsubscribers need a concatenated stream of data from every emission, you could access the last emitted value and append to it:
但是，由于BehaviorSubject保存了最后发出的值，因此这里有几个选项。如果所有订阅者都需要来自每次发射的串联数据流，您可以访问最后发射的值并将其附加到它：
userDataSource = BehaviorSubject<any[]>([]);
userData = this.userDataSource.asObservable();
updateUserData(data) {
this.userDataSource.next(this.userDataSource.value.push(data));
}
...or, in what might be considered better practice, Subscribers to this Subject could do their own transformation on the stream:
...或者，在可能被认为是更好的实践中，该主题的订阅者可以在流上进行自己的转换：
this.api.userData()
.scan((prev, current) => prev.push(current). [])
.subscribe((data) => {
this.concatenatedUserData = data;
});
