如何从角度 2 的表单组中获取所有错误？

Question

如果我像这样构建一个表单组：

    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])],
    });

如何从表单组中获取所有错误？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 会返回一个串联列表，但它始终为空，即使 passWordForm.invalid === true 时也是如此

Answer 1

我认为唯一的方法是通过执行 passwordForm.valid 来了解表单是否有效，然后遍历 Controls 对象并查找单个表单元素的错误。