将formControlName传递给Angular组件 [英] Passing formControlName into Angular component

问题描述

我有一个反应式.设置与此类似:

myForm: FormGroup;

    this.myForm= new FormGroup({
        name: new FormControl("", [Validators.required, Validators.maxLength(15), Validators.pattern('...')]),
        ...
    });

我在这样的表单上使用它:

  <input
    type="text"
    formControlName="name"
  />
  <div *ngIf="name.errors?.required">
      Name is required
  </div>
  <div *ngIf="name.errors?.maxlength">
      Name must be {{ name.errors.maxlength.requiredLength }} characters        
  </div>
  <div *ngIf="name.errors?.pattern">
      Name has invalid characters.
  </div>

这只是我表格的简化版本.我有多个输入，并且必须为每个输入创建错误div.

因此，为了解决这个问题，我尝试创建一个组件.该组件与上面的代码非常相似:

  <input
    type="text"
    [formControlName]="formControlName"
  />
  <div *ngIf="name.errors?.required">
      Name is required
  </div>
  etc...

ts文件:

@Component({
  selector: 'app-text',
  templateUrl: './text.component.html'
})
export class TextComponent  {

  @Input() formControlName: FormControl;
}

因此在我的表单上，我想按以下方式使用此组件:

<app-text [formControlName]="name"></app-text>

但是我无法使用formControlName属性.

这可能吗?

谢谢

我快到了.

我已经创建了这个StackBlitz，所以请显示我的进度:

演示

现在就在为错误而苦苦挣扎，以及如何访问formControl来检查那些错误

解决方案

您需要将表单控件传递给input元素，

  <input

    [value]="val"
    type="text"
    (input)="val=$event.target.value;onChange($event.target.value)"
    (blur)="onTouched()"
    [formControl]="control"

  >


  <span *ngIf="control && !control.valid && control.touched">
    <span class="error" *ngIf="control.errors['required']"> The field should not be empty</span>
    <span class="error" *ngIf="control.errors['email']"> The field should be an email 
    </span>
  </span>

在您的自定义组件中获取控件作为输入，并根据此显示错误.

import { Component, OnInit, forwardRef, Input, OnChanges } from '@angular/core';
import { FormControl, ControlValueAccessor, NG_VALUE_ACCESSOR, NG_VALIDATORS } from '@angular/forms';

@Component({
  selector: 'app-test',
  templateUrl: './test.component.html',
  styleUrls: ['./test.component.css'],
  providers: [
    { provide: NG_VALUE_ACCESSOR, useExisting: forwardRef(() => TestComponent), multi: true }
  ]
})
export class TestComponent implements ControlValueAccessor, OnChanges {

  constructor() { }

  propagateChange:any = () => {};

   @Input() control: FormControl;
 @Input('messageValue') _messageValue = 'whateves';  

  get messageValue() {
    return this._messageValue;
  }

  set messageValue(val) {
    console.log('set messageValue', val)
    this._messageValue = val;
    this.propagateChange(val);
  }

hi(event) {
  console.log('hi');
  console.log(event)
  this.messageValue = event;
}
  ngOnInit() {
  }

  ngOnChanges(changes) {
    console.log('changes', changes);
    this.propagateChange(this.messageValue);
  }

    writeValue(value) {
      console.log('writeValue', value);
          if (value) {
            this.messageValue = value;
      }
    }


  registerOnChange(fn) {
    console.log('onChange')
    this.propagateChange = fn;
  }

  registerOnTouched() {}

}

I have a reactive form. The setup is similar to this:

myForm: FormGroup;

    this.myForm= new FormGroup({
        name: new FormControl("", [Validators.required, Validators.maxLength(15), Validators.pattern('...')]),
        ...
    });

I use this on my form like this:

  <input
    type="text"
    formControlName="name"
  />
  <div *ngIf="name.errors?.required">
      Name is required
  </div>
  <div *ngIf="name.errors?.maxlength">
      Name must be {{ name.errors.maxlength.requiredLength }} characters        
  </div>
  <div *ngIf="name.errors?.pattern">
      Name has invalid characters.
  </div>

This is just a cut down version of my form. I have multiple input and I've had to create the error div's for each input.

So to fix this I've tried to create a component. The component is very similar to the code above:

  <input
    type="text"
    [formControlName]="formControlName"
  />
  <div *ngIf="name.errors?.required">
      Name is required
  </div>
  etc...

ts file:

@Component({
  selector: 'app-text',
  templateUrl: './text.component.html'
})
export class TextComponent  {

  @Input() formControlName: FormControl;
}

So on my form I'd like to use this component as follows:

<app-text [formControlName]="name"></app-text>

But I can't get this to work with the formControlName property.

Is this possible?

Thanks

I'm nearly there.

I've create this StackBlitz so show my progress:

Demo

Just struggling with the errors now and how to access the formControl to check for those errors

解决方案

You need to pass the form control to the input element ,

  <input

    [value]="val"
    type="text"
    (input)="val=$event.target.value;onChange($event.target.value)"
    (blur)="onTouched()"
    [formControl]="control"

  >


  <span *ngIf="control && !control.valid && control.touched">
    <span class="error" *ngIf="control.errors['required']"> The field should not be empty</span>
    <span class="error" *ngIf="control.errors['email']"> The field should be an email 
    </span>
  </span>

Get the control in your custom component as input and show the error based on this.

import { Component, OnInit, forwardRef, Input, OnChanges } from '@angular/core';
import { FormControl, ControlValueAccessor, NG_VALUE_ACCESSOR, NG_VALIDATORS } from '@angular/forms';

@Component({
  selector: 'app-test',
  templateUrl: './test.component.html',
  styleUrls: ['./test.component.css'],
  providers: [
    { provide: NG_VALUE_ACCESSOR, useExisting: forwardRef(() => TestComponent), multi: true }
  ]
})
export class TestComponent implements ControlValueAccessor, OnChanges {

  constructor() { }

  propagateChange:any = () => {};

   @Input() control: FormControl;
 @Input('messageValue') _messageValue = 'whateves';  

  get messageValue() {
    return this._messageValue;
  }

  set messageValue(val) {
    console.log('set messageValue', val)
    this._messageValue = val;
    this.propagateChange(val);
  }

hi(event) {
  console.log('hi');
  console.log(event)
  this.messageValue = event;
}
  ngOnInit() {
  }

  ngOnChanges(changes) {
    console.log('changes', changes);
    this.propagateChange(this.messageValue);
  }

    writeValue(value) {
      console.log('writeValue', value);
          if (value) {
            this.messageValue = value;
      }
    }


  registerOnChange(fn) {
    console.log('onChange')
    this.propagateChange = fn;
  }

  registerOnTouched() {}

}

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