Angular 2 - 组件内的 formControlName

我想创建一个可以与 FormBuilder API 一起使用的自定义输入组件。我该如何添加formControlName在组件内部？

模板：

<label class="custom-input__label"
          *ngIf="label">
        {{ label }}
</label>
<input class="custom-input__input" 
       placeholder="{{ placeholder }}"
       name="title" />
<span class="custom-input__message" 
      *ngIf="message">
        {{ message }}
</span>

成分：

import {
    Component,
    Input,
    ViewEncapsulation
} from '@angular/core';

@Component({
    moduleId: module.id,
    selector: 'custom-input',
    host: {
        '[class.custom-input]': 'true'
    },
    templateUrl: 'input.component.html',
    styleUrls: ['input.component.css'],
    encapsulation: ViewEncapsulation.None,
})
export class InputComponent {
    @Input() label: string;
    @Input() message: string;
    @Input() placeholder: string;
}

Usage:

<custom-input label="Title" 
           formControlName="title" // Pass this to input inside the component>
</custom-input>

你不应该添加formControlName属性到自定义组件模板中的输入字段。 您应该添加formControlName根据最佳实践，在自定义输入元素本身上。

您可以在自定义输入组件中使用的是controlValueAccessor每当您的自定义输入模板中的输入字段发生更改或模糊事件时，您的自定义输入都会更新值。

它在自定义输入的表单控件行为和为该自定义表单控件提供的 UI 之间提供连接（以更新值或其他需求）。

下面是 TypeScript 中自定义输入组件的代码。

import { Component, Input, forwardRef, AfterViewInit, trigger, state, animate, transition, style, HostListener, OnChanges, ViewEncapsulation, ViewChild, ElementRef } from '@angular/core';
import { NG_VALUE_ACCESSOR, ControlValueAccessor, FormControl } from '@angular/forms';

export const CUSTOM_INPUT_CONTROL_VALUE_ACCESSOR: any = {
    provide: NG_VALUE_ACCESSOR,
    useExisting: forwardRef(() => InputComponent),
    multi: true
};

@Component({
  selector: 'inv-input',
  templateUrl:'./input-text.component.html',
    styleUrls: ['./input-text.component.css'],
    encapsulation: ViewEncapsulation.None,
  providers: [CUSTOM_INPUT_CONTROL_VALUE_ACCESSOR],
    animations:[trigger(
        'visibilityChanged',[
            state('true',style({'height':'*','padding-top':'4px'})),
            state('false',style({height:'0px','padding-top':'0px'})),
            transition('*=>*',animate('200ms'))
        ]
    )]
})

export class InputComponent implements ControlValueAccessor, AfterViewInit, OnChanges {

    // Input field type eg:text,password
    @Input()  type = "text"; 

    // ID attribute for the field and for attribute for the label
    @Input()  idd = ""; 

    // The field name text . used to set placeholder also if no pH (placeholder) input is given
    @Input()  text = ""; 

    // placeholder input
    @Input()  pH:string; 

    //current form control input. helpful in validating and accessing form control
    @Input() c:FormControl = new FormControl(); 

    // set true if we need not show the asterisk in red color
    @Input() optional : boolean = false;

    //@Input() v:boolean = true; // validation input. if false we will not show error message.

    // errors for the form control will be stored in this array
    errors:Array<any> = ['This field is required']; 

    // get reference to the input element
    @ViewChild('input')  inputRef:ElementRef; 


    constructor() {

    }

    ngOnChanges(){

    }

    //Lifecycle hook. angular.io for more info
    ngAfterViewInit(){ 
        // set placeholder default value when no input given to pH property      
        if(this.pH === undefined){
            this.pH = "Enter "+this.text; 
        }

        // RESET the custom input form control UI when the form control is RESET
        this.c.valueChanges.subscribe(
            () => {
                // check condition if the form control is RESET
                if (this.c.value == "" || this.c.value == null || this.c.value == undefined) {
                    this.innerValue = "";      
                    this.inputRef.nativeElement.value = "";                 
                }
            }
        );
    }

   //The internal data model for form control value access
    private innerValue: any = '';

    // event fired when input value is changed . later propagated up to the form control using the custom value accessor interface
    onChange(e:Event, value:any){
        //set changed value
        this.innerValue = value;
        // propagate value into form control using control value accessor interface
        this.propagateChange(this.innerValue);

        //reset errors 
        this.errors = [];
        //setting, resetting error messages into an array (to loop) and adding the validation messages to show below the field area
        for (var key in this.c.errors) {
            if (this.c.errors.hasOwnProperty(key)) {
                if(key === "required"){
                    this.errors.push("This field is required");
                }else{
                    this.errors.push(this.c.errors[key]);
                }              
            }
        }
    }



    //get accessor
    get value(): any {
        return this.innerValue;
    };

    //set accessor including call the onchange callback
    set value(v: any) {
        if (v !== this.innerValue) {
            this.innerValue = v;
        }
    }

    //propagate changes into the custom form control
    propagateChange = (_: any) => { }

    //From ControlValueAccessor interface
    writeValue(value: any) {
        this.innerValue = value;
    }

    //From ControlValueAccessor interface
    registerOnChange(fn: any) {
        this.propagateChange = fn;
    }

    //From ControlValueAccessor interface
    registerOnTouched(fn: any) {

    }
}

下面是自定义输入组件的 HTML 模板

<div class="fg">
      <!--Label text-->
      <label [attr.for]="idd">{{text}}<sup *ngIf="!optional">*</sup></label>
      <!--Input form control element with on change event listener helpful to propagate changes -->
      <input type="{{type}}" #input id="{{idd}}" placeholder="{{pH}}" (blur)="onChange($event, input.value)">
      <!--Loop through errors-->
      <div style="height:0px;" [@visibilityChanged]="!c.pristine && !c.valid" class="error">
            <p *ngFor="let error of errors">{{error}}</p>
      </div>
</div>

下面是自定义输入组件，可以在 fromGroup 中使用或单独使用

<inv-input formControlName="title" [c]="newQueryForm.controls.title" [optional]="true" idd="title" placeholder="Type Title to search"
          text="Title"></inv-input>

以这种方式，如果您实现自定义表单控件，您可以轻松应用自定义验证器指令并在该表单控件上累积错误以显示错误。

人们可以模仿相同的风格以上述方式开发自定义选择组件、单选按钮组、复选框、文本区域、文件上传等，并根据表单控件的行为要求进行细微的更改。