自定义Angular 4验证程序取决于动态值

我必须创建一个自定义验证器

validLocation

因此，当用户输入一个值时，

searchLocation

将获得搜索的值，并通过Ajax设置

location

问题是如何在验证指令中跟踪

location

我试着使用@Input

validLocation

和

ngOnChanges

但是一旦设置了新数据，如何触发验证，这将在承诺解决后设置

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感谢您的帮助。

如果我理解正确，您可以将您的承诺或观察传达给您的指令，并在其解决时检查其价值，例如：

@Directive({ selector: '[validLocation]' })
export class ValidLocation implements OnInit {

isPromiseDone: boolean;
promise: any;

@Input()
set validLocation(passedValue: any) {
    if (!passedValue) {
        return;
    }

    const isObservable: boolean = passedValue instanceof Observable;
    const isSubscription: boolean = passedValue instanceof Subscription;
    const isPromise: boolean = passedValue instanceof Promise;

    if (isObservable) {
        this.promise = passedValue.toPromise();
    } else if (isSubscription) {
        this.promise = new Promise((resolve) => {
            (passedValue as Subscription).add(resolve);
        });
    } else if (isPromise) {
        this.promise = passedValue;
    }
    this.checkAndInitPromiseHandler();
}

constructor() {}

initPromiseHandler() {
    const promise = this.promise;
    this.isPromiseDone = false;
    const resolveLoadingState = () => {
        this.isPromiseDone = true;
        this.doSomething()
    };
    if (promise.finally) {
        promise.finally(resolveLoadingState);
    } else {
        promise
            .then(resolveLoadingState, resolveLoadingState);
    }
}

checkAndInitPromiseHandler() {
    if (this.promise) {
        this.initPromiseHandler();
    }
}

ngOnInit() {
    this.checkAndInitPromiseHandler();
}

doSomething(){}
}

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你能分享更多的代码或添加你的样本吗？