如何从角度2中的表单组中获取所有错误？

Question

如果我建一个表单组这样的：

this.passWordForm = this._formBuilder.group({ 
     "previous_password": [this.changePassword.previous_password, Validators.compose([Validators.required])], 
     "new_password": [this.changePassword.new_password, Validators.compose([Validators.required,PasswordValidator.validate])], 
    }); 

我怎么会得到从表单组中的所有错误？我一直在做的是这样的：

<form role="form" [formGroup]="passWordForm" novalidate (ngSubmit)="submitChangePassword()"> 
<input [(ngModel)]="changePassword.previous_password" formControlName="previous_password" name="previous_password" type="password" placeholder="Previous Password" class="form-control" required> 
<input formControlName="new_password" [(ngModel)]="changePassword.new_password" name="new_password" type="password" placeholder="New Password" class="form-control" required> 
<div *ngIf="passWordForm.invalid === true && passWordForm.controls['new_password'].errors"> 
    <div *ngFor="let line of passWordForm.controls['new_password'].errors.message" class="alert alert-danger">{{line}}</div> 
</div> 
<div *ngIf="passWordForm.invalid === true && passWordForm.controls['previous_password'].errors"> 
    <div class="alert alert-danger">{{passWordForm.controls['previous_password'].errors.message}}</div> 
</div> 
</form> 

我希望passWordForm.errors会返回一个连续清单，但它总是空，即使passWordForm.invalid === true

Answer 1

，我认为是唯一的方式知道如果表单通过执行passwordForm.valid，然后迭代Controls对象并查找单个表单元素的错误，该方法是有效的。