Angular 5 SelectControlValueAccessor 实现错误

Question

我想在 Angular 5 中创建一个自定义选择输入控件。我有一个实现 SelectControlValueAccessor 的组件。当我实现如下所示的课程时。它在代码注释中给出了错误。

import { Component, Input, forwardRef, SimpleChanges, OnChanges } from '@angular/core';
import {  SelectControlValueAccessor } from '@angular/forms';
import { SELECT_VALUE_ACCESSOR } from '@angular/forms/src/directives/select_control_value_accessor';

@Component({    
    selector: 'select-input',
    template: ` `,
    providers: [
        {   
          provide: SELECT_VALUE_ACCESSOR,
            useExisting: forwardRef(() => SelectInputComponent),
            multi: true
        }
    ]
})

/*
[ts]
Class 'SelectInputComponent' incorrectly implements class 'SelectControlValueAccessor'. Did you mean to extend 'SelectControlValueAccessor' and inherit its members as a subclass?
  Property '_renderer' is missing in type 'SelectInputComponent'.
class SelectInputComponent
*/
export class SelectInputComponent implements SelectControlValueAccessor {
  value: any;  onChange: (_: any) => void;
  onTouched: () => void;
  compareWith: (o1: any, o2: any) => boolean;
  writeValue(value: any): void {
    throw new Error("Method not implemented.");
  }
  registerOnChange(fn: (value: any) => ): void {
    throw new Error("Method not implemented.");
  }
  registerOnTouched(fn: () => ): void {
    throw new Error("Method not implemented.");
  }
  setDisabledState(isDisabled: boolean): void {
    throw new Error("Method not implemented.");
  }



}

我的配置如下： Typescript：2.5.3 Angular：5.2.11 VS Code：1.24.1

Answer 1

来自文档https://v6.angular.io/api/forms/SelectControlValueAccessor

SelectControlValueAccessor是指令而不是接口

班级：

import { Component, OnInit, Output, EventEmitter, Renderer2, ElementRef } from '@angular/core';
import { NG_VALUE_ACCESSOR, SelectControlValueAccessor } from '@angular/forms';

@Component({    
    selector: 'select-input',
    template: ` `,
    providers: [
        {   
            provide: NG_VALUE_ACCESSOR,
            useExisting: forwardRef(() => SelectInputComponent),
            multi: true
        }
    ]
})


export class SelectInputComponent extends SelectControlValueAccessor {
  value: any;
  onChange: (_: any) => void;
  onTouched: () => void;

   compareWith: (o1: any, o2: any) => boolean;
   compareFn(c1: any, c2: any): boolean {
       return c1 && c2 ? c1.key === c2.key : c1 === c2;
   }
  writeValue(value: any): void {
        if (value) {
           this.value.emit(value);        }
    }
    registerOnChange(fn: (value: any) => any): void {
        this.onChange = fn;
    }
    registerOnTouched(fn: () => any): void {
        this.onTouched = fn;
    }
    setDisabledState(isDisabled: boolean): void {
        throw new Error('Method not implemented.');
    }

    constructor(_renderer: Renderer2, _elementRef: ElementRef) {
        super(_renderer, _elementRef);
    }
}

HTML - 选择：

<select class="form-control" [compareWith]="compareFn"  [(ngModel)]="value">
     <option value="">Choose a option</option>
     <option *ngFor="let option of options" [ngValue]="option">{{option.name}}</option>
 </select>