嵌套的Angular元素拋出ExpressionChangedAfterItHaHasBeenCheckedError

Question

我已經對此問題進行了一些研究，但現在不確定它是錯誤還是我的實現出現問題。

我有一個使用服務來獲取一些數據的元素，然后將數據傳遞給子元素，但是當我更新數據時，我遇到了這個錯誤。

父元素

import { Component, OnInit, ViewEncapsulation} from '@angular/core';
import { TestService } from '../services/test.service';

@Component({
    selector: 'dm-element-with-service-test',
    templateUrl: './element-with-service-test.component.html',
    encapsulation: ViewEncapsulation.Emulated
})
export class ElementWithServiceTestComponent implements OnInit {
currentCount: number;

constructor(private testService: TestService) { }

    ngOnInit() {
        this.testService.count.subscribe(count => this.currentCount = count); 
    }

    count() {
        this.testService.addCount();
    }

}

父元素視圖

<div>
    <button (click)="count()">count</button>
    <element-test [myNumber]="currentCount"></element-test>
</div>

子元素

import { Component, OnInit, ViewEncapsulation, Input } from '@angular/core';

@Component({
    selector: 'dm-element-test',
    templateUrl: './element-test.component.html',
    encapsulation: ViewEncapsulation.Emulated
})
export class ElementTestComponent implements OnInit {
    @Input() myNumber: number;
    constructor() { }

    ngOnInit() {
    // do stuff...
    }
}

子元素視圖

<p>
    current number in this component: {{myNumber}}
</p>

應用模塊

import { BrowserModule } from '@angular/platform-browser';
import { NgModule, Injector, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
import { AppComponent } from './app.component';
import { ElementTestComponent } from './element-test/element-test.component';
import { createCustomElement } from '@angular/elements';
import { ElementWithServiceTestComponent } from './element-with-service-test/element-with-service-test.component';


@NgModule({
    declarations: [
        AppComponent,
        ElementTestComponent,
        ElementWithServiceTestComponent
    ],
    imports: [
        BrowserModule
    ],
    providers: [],
    schemas: [CUSTOM_ELEMENTS_SCHEMA ],
    entryComponents: [ElementTestComponent, ElementWithServiceTestComponent]
})
export class AppModule {
    constructor(private injector: Injector) {
        const el = createCustomElement(ElementTestComponent, { injector });
        const el2 = createCustomElement(ElementWithServiceTestComponent, { injector });
        customElements.define('element-test', el);
        customElements.define('element-with-service-test', el2);
    }
    ngDoBootstrap() { }
}

指數

<div class="tests">
     <element-with-service-test></element-with-service-test>
</div>

加載應用程序時，一切正常，但是如果單擊“計數”按鈕，則會出現該錯誤。

Answer 1

當您更改子組件中從父代傳遞的數據時，總是會發生該錯誤。 你應該

1）不這樣做

2）修改數據時，請使用changeDetectorRef.detectChanges() 。

https://blog.angularindepth.com/everything-you-need-to-know-about-the-expressionchangedafterithasbeencheckederror-error-e3fd9ce7dbb4