javascript - Angular create Dynamic Component recursively

Question

I am trying to build a dynamic component based on a Config. The component would read the config recursively and create the component. It is found that the method ngAfterViewInit() would only be called twice.

@Component({
    selector: "dynamic-container-component",
    template: `
        <div #container
            draggable="true"
            (dragstart)="dragstart($event)"
            (drop)="drop($event)"
            (dragover)="dragover($event)"
            style="border: 1px solid; min-height: 30px"></div>
    `
})
export default class DynamicContainerComponent {

    @Input()
    dynamicConfig: DynamicConfig;

    @ViewChild("container", {read: ElementRef})
    private elementRef: ElementRef;

    private isContainer: boolean;
    private componentRef: ComponentRef<any>;
    private componentRefs: ComponentRef<any>[] = [];
    
    constructor(
        private componentFactoryResolver: ComponentFactoryResolver,
        private injector: Injector,
        private viewContainer: ViewContainerRef,
        private render: Renderer2
    ){
        console.log("running");
    }

    ngAfterViewInit(){
        
        if (this.dynamicConfig){
            console.log(this.dynamicConfig)
            if (this.dynamicConfig.getType() == ComponentType.INPUT){
                this.isContainer = false;
                let componetFactory: ComponentFactory<InputComponent> = 
                    this.componentFactoryResolver.resolveComponentFactory(InputComponent);
                this.componentRef = this.viewContainer.createComponent(componetFactory);
                this.render.appendChild(this.elementRef.nativeElement, this.componentRef.location.nativeElement);
            }else {
                this.isContainer = true;
                let items: DynamicConfig[] = this.dynamicConfig.getItems();
                if (items){
                    for (var i=0; i<items.length; i++){
                        let item: DynamicConfig = items[i];
                        let componetFactory: ComponentFactory<DynamicContainerComponent> = 
                            this.componentFactoryResolver.resolveComponentFactory(DynamicContainerComponent);
                        let componentRef: ComponentRef<DynamicContainerComponent> = 
                            this.viewContainer.createComponent(componetFactory);
                        componentRef.instance.dynamicConfig = item;
                        this.componentRefs.push(componentRef);
                        this.render.appendChild(this.elementRef.nativeElement, componentRef.location.nativeElement);
                    }
                }
            }
        }else {
            console.log("config does not exist");
        }

    }

    dragstart(event){
        debugger;
    }

    drop(event){
        debugger;
    }

    dragover(event){
        debugger;
        event.preventDefault();
    }


}

The Component would be created by other component by the following code. If The Dynamic Component would create another Dynamic Component by componentFactoryResolver.

    var configJson = {
        type: ComponentType.CONTAINER,
        items: [
            {
                type: ComponentType.CONTAINER,
                items: [{
                    type: ComponentType.CONTAINER,
                    items: [{
                        type: ComponentType.CONTAINER,
                        items: [{
                            type: ComponentType.INPUT
                        }]
                    }]
                }]
            }
        ]
    }

    this.config = new DynamicConfig();
    this.config.assign(configJson);
    console.log(this.config);

Update I found a similar issue in github: https://github.com/angular/angular/issues/10762

I have done something suggested by other people. but I think it is just a dirty fix.

ngAfterViewInit(){
    setTimeout(function(){
        if (this.dynamicConfig){
            console.log(this.dynamicConfig)
            if (this.dynamicConfig.getType() == ComponentType.INPUT){
                this.isContainer = false;
                let componetFactory: ComponentFactory<InputComponent> = 
                    this.componentFactoryResolver.resolveComponentFactory(InputComponent);
                this.componentRef = this.viewContainer.createComponent(componetFactory);
                this.render.appendChild(this.elementRef.nativeElement, this.componentRef.location.nativeElement);
            }else {
                this.isContainer = true;
                let items: DynamicConfig[] = this.dynamicConfig.getItems();
                if (items){
                    for (var i=0; i<items.length; i++){
                        let item: DynamicConfig = items[i];
                        let componetFactory: ComponentFactory<DynamicContainerComponent> = 
                            this.componentFactoryResolver.resolveComponentFactory(DynamicContainerComponent);
                        let componentRef: ComponentRef<DynamicContainerComponent> = 
                            this.viewContainer.createComponent(componetFactory);
                        componentRef.instance.dynamicConfig = item;
                        this.componentRefs.push(componentRef);
                        this.render.appendChild(this.elementRef.nativeElement, componentRef.location.nativeElement);
                    }
                }
            }
        }else {
            console.log("config does not exist");
        }
    }.bind(this))
}

标签： javascriptangulartypescript

Answer 1

By the time you create your dynamic component angular has almost finished change detection cycle.

This way you can either run:

componentRef.changeDetectorRef.detectChanges()

Note: setTimeout has similar effect but fires change detection cycle on the whole app

or rename lifecycle hook to ngOnInit

Also you're passing wrong input to dynamic component:

let item: DynamicConfig = items[i];
          ^^^^^^^^^^^^^
    but it is not DynamicConfig instance but rather plain object
...
componentRef.instance.dynamicConfig = item;

it should be:

let item: any = items[i];
const config = new DynamicConfig();
config.assign(item);
componentRef.instance.dynamicConfig = config;

Ng-run Example