Angular 4订阅方法调用多次
我正在创建一个全局模态组件。 我的问题是,当我调用subscribe方法时,它会根据调用的模态数多次调用。 如何防止对observable subscribe方法的多次调用?请检查我下面的代码。提前谢谢 modal.model.tsAngular 4订阅方法调用多次,angular,rxjs,typescript2.0,Angular,Rxjs,Typescript2.0,我正在创建一个全局模态组件。 我的问题是,当我调用subscribe方法时,它会根据调用的模态数多次调用。 如何防止对observable subscribe方法的多次调用?请检查我下面的代码。提前谢谢 modal.model.ts export class Modal { title: string; message: string; visible: boolean = false; } 模态服务 import { Injectable } from '@angular/cor
export class Modal {
title: string;
message: string;
visible: boolean = false;
}
模态服务
import { Injectable } from '@angular/core';
import { Modal } from './modal.model';
import { Observable } from 'rxjs';
import { Subject } from 'rxjs/Subject';
@Injectable()
export class ModalService {
static readonly YES = 1;
static readonly NO = 0;
private modal = new Modal();
private subject = new Subject<Modal>();
private action = new Subject<number>();
confirmationDialog(message) {
this.modal.title = 'Confirmation';
this.modal.message = message;
return this;
}
show() {
this.modal.visible = true;
this.setModal(this.modal);
return this;
}
setAction(action: number) {
this.action.next(<number>action);
}
getAction(): Observable<any> {
return this.action.asObservable();
}
setModal(alert: Modal) {
this.subject.next(<Modal>alert);
return this;
}
getModal(): Observable<any> {
return this.subject.asObservable();
}
}
调用模态组件
import { Component, OnInit } from '@angular/core';
import { ModalService } from './modal.service';
import { Modal } from './modal.model';
@Component({
selector: 'modal',
templateUrl: './modal.component.html',
styleUrls: ['./modal.component.css']
})
export class ModalComponent implements OnInit {
public modal: Modal;
constructor(private modalService: ModalService){}
ngOnInit() {
this.modalService.getModal().subscribe((modal: Modal) => {
this.modal = modal;
console.log(modal);
});
}
no() {
this.modalService.setAction(0);
this.modalService.close();
}
yes() {
this.modalService.setAction(1);
this.modalService.close();
}
}
showModal() {
this.modalService.confirmationDialog('Are you sure you want to save this record?').show();
this.modalService.getAction().subscribe(response => {
if(response === ModalService.NO) {
return;
}
console.log('call mutiple times');
});
}
下面是控制台日志上输出的屏幕截图。
将您的订阅移动到ctor。例:
private unsubscribe: Subject<void> = new Subject<void>();
constructor(private modalService: ModalService){
this.modalService.getModal()
.takeUntil(this.unsubscribe)
.subscribe((modal: Modal) => {
this.modal = modal;
console.log(modal);
});
}
ngOnInit() {
}
ngOnDestroy() {
this.unsubscribe.next();
this.unsubscribe.complete();
}
private退订:主题=新主题();
构造函数(专用modalService:modalService){
this.modalService.getModal()
.takeUntil(此.取消订阅)
.订阅((模式:模式)=>{
this.modal=modal;
控制台日志(模态);
});
}
恩戈尼尼特(){
}
恩贡德斯特罗(){
this.unsubscribe.next();
此为.unsubscribe.complete();
}
我认为在模态组件中使用异步管道会更容易:
import { Component } from '@angular/core';
import { Observable } from 'rxjs';
import { ModalService } from './modal.service';
import { Modal } from './modal.model';
@Component({
selector: 'modal',
templateUrl: './modal.component.html',
styleUrls: ['./modal.component.css']
})
export class ModalComponent {
public modal$: Observable<Modal>;
constructor(private modalService: ModalService){
this.modal$ = this.modalService.getModal();
}
no() {
this.modalService.setAction(0);
this.modalService.close();
}
yes() {
this.modalService.setAction(1);
this.modalService.close();
}
}
这确保Angular在组件销毁时自行清理订阅
对于订阅,在创建模式时,可以使用take
操作符,如果发出x值,则完成订阅
this.modalService.getAction().take(1).subscribe(response => {
if(response === ModalService.NO) {
return;
}
console.log('call mutiple times');
});
我假设您只需要1个值(因为这是一个简单的对话框)。只是当您的组件被销毁时,不要忘记取消订阅modalService。。例如
...
export class ModalComponent implements OnInit, OnDestroy {
public modal: Modal;
constructor(private modalService: ModalService){}
public ngOnDestroy(): void {
this.modalService.unsubscribe(); // or something similar
}
}
可能发生的情况是,每次打开模式时,订阅都会保持持久性,并将执行+1次,但在模式关闭或销毁时使用destroy,您也将删除订阅
或者更好,基本上每次订阅时,您都在创建一个新的可观察对象,但是您可以重用您创建的第一个,应用一个简单的验证(注意,在这种情况下,您不应该使用unsubscribe)。例如
有很多方法可以防止触发订阅者不止一次。感谢您的建议,但仍然不起作用。在Ngondestry lifecyclehook或通过
takeWhile
或takeUntil
在组件构造函数内部订阅而不清理组件构造函数是一种不好的做法。这更多的是对其多个订阅触发进行故障排除。不管怎样,说得对。更新。可能您的应用程序尚未导入所有运算符,您可以使用:import'rxjs/add/operator/take'导入运算符代码>谢谢,您的代码正在运行,take()方法成功了。但是,如果我单击按钮两次,模式将弹出。有什么想法吗?第二种方法是显示错误,类型Observable没有属性Observators。
...
export class ModalComponent implements OnInit, OnDestroy {
public modal: Modal;
constructor(private modalService: ModalService){}
public ngOnDestroy(): void {
this.modalService.unsubscribe(); // or something similar
}
}
if (this.modalService.getModal().observers.length === 0) {
this.modalService.getModal().subscribe((modal: Modal) => {
this.modal = modal;
console.log(modal);
});
}