如何解决如何检测Angular 9中所有组件的共享数据服务更改?
我正在使用自定义库编写Angular应用程序。 有几个嵌套组件。
在子组件中,我单击按钮以设置表单中的新数据。
<button ... (click)="createFile()" >Create file</button>
child.component.html
<form [formGroup]="starterFormArray" *ngIf="starterFormWithStepper">
<mat-horizontal-stepper #stepper>
<mat-step *ngFor="let step of starterFormSteps; let index = index; let last = last;">
<ng-template matStepLabel>{{ step.label }}</ng-template>
<formly-form
[form]="starterFormArray.at(index)"
[model]="starterModel"
[fields]="step.fields"
[options]="starterOptions[index]">
</formly-form>
</mat-step>
</mat-horizontal-stepper>
<div class="wrapper-actions-for-stepper">
<div class="part-toolbar">
<button mat-stroked-button (click)="goBack(stepper)" type="button" [disabled]="stepper.selectedIndex === 0">Back</button>
<button mat-stroked-button (click)="goForward(stepper)" type="button" [disabled]="stepper.selectedIndex === starterFormSteps.length-1">Next</button>
</div>
<div class="part-toolbar">
<button mat-raised-button [disabled]="!starterFormArray.valid" (click)="createFile()" >Create file</button>
</div>
</div>
</form>
子组件函数CreateFile()
在共享数据服务内设置var
child.component.ts
@Component({
selector: 'foo-child',templateUrl: './child.component.html',styleUrls: ['./child.component.scss'],providers: [ DataService,provideParent( ParentComponent,BaseComponent ) ]
})
export class ChildComponent extends BaseComponent implements OnInit,AfterViewInit,AfterViewChecked,AfterContentInit {
starterForm: FormGroup;
starterFormArray: FormArray;
starterModel: CurrentProject;
starterFormFields: Array<FormlyFieldConfig>;
starterFormSteps: Array<StepType>;
starterOptions: any;
starterFormWithStepper: boolean;
constructor(elRef: ElementRef,data: DataService ) {
super(elRef);
this.sharedData = data;
}
createFile() {
this.sharedData.changeUserFile( this.starterModel );
}
}
sharedData
参数在BaseComponent
中声明。
base.component.ts
import {DataService} from '../../common/services/data.service';
export class BaseComponent{
public sharedData: DataService;
}
在共享服务中,我试图提供一种方法来检测使用该共享库的所有组件的所有更改。
data.service.ts
@Injectable()
export class DataService{
public file: BehaviorSubject<CurrentProject> = new BehaviorSubject(null);
public changeFile = this.file.asObservable();
constructor( public cdref: ChangeDetectorRef ) {}
changeUserFile( newData: CurrentProject ){
this.file.next(newData);
alert(JSON.stringify( this.file.getValue())); //<-- it works !
this.cdref.detectChanges();
}
}
但是parent.component.ts
从未检测到更改。
parent.component.ts
@Component({
selector: 'foo-parent',templateUrl: './parent.component.html',styleUrls: ['./parent.component.scss'],encapsulation: ViewEncapsulation.None,provideParent( ParentComponent ) ]
})
export class ParentComponent extends BaseComponent implements OnInit,OnChanges{
@Input() fileName: string;
constructor(elRef: ElementRef,data: DataService,private cdref: ChangeDetectorRef ) {
this.sharedData = data;
}
ngOnInit() {
super.ngOnInit();
this.sharedData.changeFile.subscribe( ( fileModified) => {
if ( ( fileModified !== null ) && ( fileModified.getFileName() !== this.fileName ) ) {
alert('Never Called');
this.fileName = fileModified.getFileName();
}
});
}
ngOnChanges(changes: SimpleChanges) {
alert('change only when the page is loaded');
}
}
由于某些原因,parent.component.ts
无法实现数据,this.sharedData.changeFile.subscribe()
无法正常工作。
我测试了ngOnChanges
和ChangeDetectorRef
,但没有成功。
有人知道这个问题吗?
解决方法
每个组件都是类的另一个实例。扩展并不能使它们共享相同的值,而是将服务实例化一次,并在服务模块范围内的各处注入构造函数,从而获得相同的实例。
简单的解决方案是注入DataService并对其进行订阅,这将指向应用程序中各处的相同引用。
例如伪代码:
DataService
class DataService {
public file: BehaviorSubject<CurrentProject> = new BehaviorSubject(null);
setDataMethod(newData: CurrentProject) {
this.file.next(newData);
}
}
ParentComp
class ParentComp extends BaseComp implements OnInit{
constructor(private (or public to access from html) dataService: DataService) {}
ngOnInit(){
this.dataService.file.subscribe(changedFile => {
//do stuff
})
}
}
或DataService在提供程序中的同一模块中的任何其他相关/不相关子组件
class ParentComp extends BaseComp implements OnInit {
constructor(private (or public to access from html) dataService: DataService) {}
ngOnInit(){
this.dataService.file.subscribe(changedFile => {
//do stuff
})
}
}
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