javascript - 条件表单验证器 Angular2

Question

我正在尝试根据选定的单选按钮运行表单验证器，因此如果选择了 instagram，将运行一个验证器，如果选择了 facebook，将运行另一个验证器。我的组件模板如下:

<div class="form-group" [ngClass]="{ 'has-error' : !requestURL.valid && submitAttempt }">

                        <div class="radio">

                            <label for="instagram">
                                <input type="radio" 
                                    name="socialmedia" 
                                    id="instagram" 
                                    value="instagram" 
                                    [checked]="selectedSourceType === 'instagram'"
                                    (click)="updateSelectedSourceType('instagram')">

                                    <i class="fa fa-instagram"></i>
                            </label>

                            <label for="facebook">
                                <input type="radio" 
                                    name="socialmedia" 
                                    id="facebook" 
                                    value="facebook" 
                                    [checked]="selectedSourceType === 'facebook'"
                                    (click)="updateSelectedSourceType('facebook')">

                                    <i class="fa fa-facebook"></i>
                            </label>

                        </div>

                        <label for="requestSource">Submit URL</label>
                        <span *ngIf="requestURL.hasError('alreadyTracked')" class="already-following">Already Following This User</span>

                        <input type="text" 
                            id="requestSource" 
                            class="form-control" 
                            placeholder="Enter a website, Facebook Page or Instagram handle" 
                            ngControl="requestURL">

因此，单击 selectedSourceType 会切换，其值应确定运行哪个验证器。但是由于构造函数，运行时的原始值是运行的验证器，即使选择了另一个单选按钮也是如此。有人对此有任何可能的解决方案吗？这是我的类(class)的内容，验证器现在只是一个字符串检查，并且正在按预期单独工作:

theForm: ControlGroup;
requestURL: Control;
submitAttempt: boolean = false;
isLoading: boolean = false;
selectedSourceType:string = 'facebook';

validationUrls = {
    instagram: 'post-ig-url?src=',
    facebook: 'post-fb-url?src='
}

constructor(private _applicationService:AppService,
    private _elRef:ElementRef,
    private _router:Router,
    private _http:Http,
    private _builder:FormBuilder) {

    super(_elRef, _applicationService, _router);

    this.createRequestURLControl(CustomValidators.facebookURL);

    this.theForm = _builder.group({
        requestURL: this.requestURL
    });
}


requestSource(form){
    console.log('Selected source:', this.selectedSourceType);

    this.isLoading = true;
    this.submitAttempt = true;

    let sub = this._http.post(this.validationUrls[this.selectedSourceType] + form.requestURL, '')
        .subscribe(data => {
            console.log("URL Submitted for review", data);
            this.isLoading = false;
        }, error => {
            console.info(error.json().message);
        });

    this.addSubscription(sub);
}

createRequestURLControl(validator:any) {
    this.requestURL = new Control('', Validators.compose([validator, Validators.required]) );
}

updateSelectedSourceType(sourceType:string) {
    this.selectedSourceType = sourceType;

    // update validators
    if (sourceType === 'facebook') {
        this.createRequestURLControl(CustomValidators.facebookURL);
    } else {
        this.createRequestURLControl(CustomValidators.instagramURL);
    }
    // clear input
}

Answer 1

只需将验证器设为组件的方法或当前作用域中的闭包，这样它就可以访问组件的值。

class MyComponent {
  someValidator(c:Control) {
    if(this.radio...) {
      ...
    }
  }

  createRequestURLControl(validator:any) {
      this.requestURL = new Control('', Validators.compose([(c:Control) => this.someValidator(c), Validators.required]) );
  }
}

我没有调查您想要有条件的确切验证器或如何评估条件，但您应该明白了。

重要的是使用 ()=>，这样 this 就会在验证器方法中继续工作。