Angular ngForm自定义输入数字选择器中的零值

我有个问题

• 在服务器端PHP上，api返回json，其中某些项具有零值。 我在PHP端使用JSON\u数字\u检查

• 在角度方面：

• 我的问题是当match.scoreq1=0=>此值不显示在我的输入=>它保持空白！ 当值为零时，它似乎是“未定义的”

注意：match.scoreq1可以为null=>在这种情况下，我希望显示为空

---

问题在哪里？ngModel？ControlValueAccessor？

我想这是因为在

writeValue（value）

方法中，您检查了

if（value）

， 但如果值为0，则实际计算结果为false，并且永远不会设置组件的值。只需替换if语句，如下所示：

writeValue(value) {
   if (value !== null && value !== undefined) {
     this.value = value;
   }
}

<div class="input-group mb-3 input-md">
  <div class="input-group-prepend">
    <span class="input-group-text decrease" (click)="decrease();">-</span></div>
  <input [name]="name" [(ngModel)]="value" class="form-control counter" type="number" step="1">
  <div class="input-group-prepend">
    <span class="input-group-text increase" (click)="increase();" style="border-left: 0px;">+</span></div>
</div>

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

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

  @Input()
  name: string;
  @Input() val: number;
  // Both onChange and onTouched are functions
  onChange: any = () => { };
  onTouched: any = () => { };

  get value() {
    return this.val;
  }

  set value(val) {
    this.val = val;
    this.onChange(val);
    this.onTouched();
  }
  // We implement this method to keep a reference to the onChange
  // callback function passed by the forms API
  registerOnChange(fn) {
    this.onChange = fn;
  }
  // We implement this method to keep a reference to the onTouched
  // callback function passed by the forms API
  registerOnTouched(fn) {
    this.onTouched = fn;
  }
  // This is a basic setter that the forms API is going to use
  writeValue(value) {
    if (value) {
      this.value = value;
    }
  }

  decrease() {
    if (this.value === 0 || this.value === null) {
      this.value = null;
    } else {
      this.value--;
    }
  }

  increase() {
    if (isNaN(this.value) || this.value === null) {
      this.value = 0;
    } else {
      this.value++;
    }
  }

}

writeValue(value) {
   if (value !== null && value !== undefined) {
     this.value = value;
   }
}