角度5 |具有ControlValueAccessor的ReactiveForm |不触发onChange [英] Angular 5 | ReactiveForm with ControlValueAccessor | onChange is not triggered
问题描述
我有一个自定义的ControlValueAccessor,它仅将货币符号附加在输入上.
I have a custom ControlValueAccessor which simply appends a currency symbol on an input.
@Component({
selector: 'app-currency-input',
templateUrl: './currency-input.component.html',
styleUrls: ['./currency-input.component.scss'],
providers: [
CurrencyPipe,
{
provide: NG_VALUE_ACCESSOR,
useExisting: forwardRef(() => CurrencyInputComponent),
multi: true
}
]
})
export class CurrencyInputComponent implements ControlValueAccessor {
@Input() class = '';
currencyValue: string;
onChange: (value: number) => void;
onTouched: () => void;
constructor(
private currencyPipe: CurrencyPipe
) { }
parseToNumber(currencyString: string) {
this.onChange(this.currencyPipe.parse(currencyString));
}
transformToCurrencyString(value: number): string {
return this.currencyPipe.transform(value);
}
writeValue(value: number): void {
if (value !== undefined) {
this.currencyValue = this.transformToCurrencyString(value);
}
}
registerOnChange(fn: any): void {
this.onChange = fn;
}
registerOnTouched(fn: any): void {
this.onTouched = fn;
}
}
CurrencyPipe
只是将字符串解析为数字,然后将数字转换为货币字符串(具有本地化的十进制分隔符和货币符号).
The CurrencyPipe
just parses the string to number and transforms a number to a currency string (with localized decimal seperator and currency symbol).
当我尝试像这样使用ReactiveForms时:
When I try to use ReactiveForms like this:
<app-currency-input
name="amount"
class="value-box"
formControlName="amount"
required
></app-currency-input>
...然后手动输入不会触发onChange()
.
... then onChange()
is not triggered on manual input.
我有一个解决方法,我先订阅控件的valueChanges
,然后执行
I have a workaround, where I subscribe to the valueChanges
of the control and then do a
control.patchValue(newValue, { emitModelToViewChange: true })
...成功触发了ControlValueAccessor的onChange
. (不带选项的patchValue
会执行相同的操作,因为true
是此选项的默认值.我只是想在此指出罪魁祸首.)
... which successfully triggers the onChange
for the ControlValueAccessor. (A patchValue
without options would do the same, because true
is the default value for this option. I just wanted to point out the culprit here.)
但是我很想使用一个内置的解决方案,该解决方案无法解决额外的必要检查和至少两个valueChanges.
But I would love to use an inbuilt solution which does not resolve in additional needed checks and at least two valueChanges.
一个简化的Plunker试用: https://embed.plnkr.co/c4YMw87FiZMpN5Gr8w1f/一个>
请参见src/app.ts
中注释掉的代码.
A simplified Plunker to try it out: https://embed.plnkr.co/c4YMw87FiZMpN5Gr8w1f/
See the commented out code in src/app.ts
.
推荐答案
尝试类似的方法
import { Component, Input, forwardRef } from '@angular/core';
import { CurrencyPipe, } from '@angular/common';
import { ReactiveFormsModule, NG_VALUE_ACCESSOR, FormControl, ControlValueAccessor } from '@angular/forms';
import { Subscription } from 'rxjs/Subscription';
@Component({
selector: 'currency-input',
template: `<input [formControl]="formControl" (blur)="onTouched()"/>`,
styles: [`h1 { font-family: Lato; }`],
providers: [
CurrencyPipe,
{
provide: NG_VALUE_ACCESSOR,
useExisting: forwardRef(() => CurrencyInputComponent),
multi: true
}
]
})
export class CurrencyInputComponent implements ControlValueAccessor {
constructor(private currencyPipe: CurrencyPipe) { }
private onChange: Function;
private onTouched: Function;
formControl = new FormControl('');
subscription: Subscription;
ngOnInit() {
this.subscription = this.formControl.valueChanges
.subscribe((v) => {
this.onChange && this.onChange(this.transform(v));
})
}
ngOnDestroy() {
this.subscription.unsubscribe();
}
writeValue(val) {
this.formControl.setValue(this.transform(val), { emitEvent: false });
}
registerOnChange(fn) {
this.onChange = fn;
}
registerOnTouched(fn) {
this.onTouched = fn;
}
private transform(val: string) {
return this.currencyPipe.transform(val, 'USD')
}
}
请注意,我正在使用ReactiveFormsModule
,因此您需要将其导入到模块中.
Please note that I'm using the ReactiveFormsModule
so you need to import it in your module.
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