您应该只创建一个实现以下功能的组件ControlValueAccessor https://angular.io/api/forms/ControlValueAccessor接口,然后将其与ngModel
选择元素的。为了更好地使用,我建议首先实现一个抽象类:
import { Provider, forwardRef, Type, OpaqueToken } from '@angular/core';
import { ControlValueAccessor, NG_VALUE_ACCESSOR } from '@angular/forms';
export abstract class AbstractValueAccessor implements ControlValueAccessor {
private _value: any = null;
public onChange = (_) => { };
public onTouched = () => { };
public get value(): any {
return this._value;
}
public set value(v: any) {
if (v !== this._value) {
this._value = v;
this.onChange(v);
}
}
public writeValue(value: any) {
this._value = value;
this.onChange(value);
}
public registerOnChange(fn: (_: any) => void): void {
this.onChange = fn;
}
public registerOnTouched(fn: () => void): void {
this.onTouched = fn;
}
}
export function MakeProvider(type: any) {
return {
provide: NG_VALUE_ACCESSOR,
useExisting: forwardRef(() => type),
multi: true
};
}
有关实现的值访问器的外观和工作原理的更多信息可以找到here https://angular.io/api/forms/DefaultValueAccessor。有关角度外观中各种评估器实现的信息here https://angular.io/api?query=ValueAccessor.
然后用它扩展你的组件:
import { Component, ChangeDetectionStrategy, Input, SimpleChanges, OnChanges } from '@angular/core';
import { BehaviorSubject } from 'rxjs';
import { AbstractValueAccessor, MakeProvider } from './abstract-value-accessor';
@Component({
selector: 'custom-select',
templateUrl: './custom-select.component.html',
providers: [MakeProvider(CustomSelectComponent)],
changeDetection: ChangeDetectionStrategy.OnPush
})
export class CustomSelectComponent extends AbstractValueAccessor implements OnChanges {
private data$$ = new BehaviorSubject<any[]>([]);
@Input()
public dataKey: string;
public data$ = this.data$$.asObservable();
public get hasData$() {
return this.data$.map(data => data.length > 0);
}
constructor(private dataService: MyDataService) {
super();
}
ngOnChanges(changes: SimpleChanges) {
if(changes.dataKey && changes.dataKey.currentValue) {
this.getData(changes.dataKey.currentValue);
}
}
private getData(dataKey: string) {
this.dataService.get(dataKey).take(1).subscribe(data => this.data$$.next(data));
}
}
在组件的模板中,将其绑定到选择:
<select [(ngModel)]="value" *ngIf="hasData$ | async">
<option [value]="option.value" *ngFor="let option of data$ | async">{{ option.name }}</option>
</select>
然后你可以在任何你想要的地方使用它,例如:
<custom-select dataKey="test"></custom-select>
注意:此代码未经测试,仅提供正确方向的方法。