FormControl 上的 ValueChanges 在 Form.enable 时触发，即使有 emitEvent: false

Question

FIXED: This issue was a bug that is now fixed in versions above 6.0.0 and 5.2.5, according to the GH issue: github.com/angular/angular/issues/12366

使用 Angular (4.x) 我使用 ReactiveForms 并在我的 FormControl（“输入”）上订阅了 valueChanges，如下所示：

export class App {
  version:string;
  formControl = new FormControl('default', []);
  form = this.fb.group({
        input: this.formControl,
        input2: ('',[])
    });
  
  constructor(private fb: FormBuilder) {
    this.version = `Angular v${VERSION.full}`
  }
  
  ngOnInit() {
    this.formControl.valueChanges.subscribe(value => doSomething(value));
  }

所以现在我可以对我的 FormControl 值的变化做出反应，但我当然是从某个地方开始填写表单的值，所以我使用 form.patchValue(data) 来这样做。

由于这不是用户更改，我不想对此做出反应，所以添加标志 emitEvent: false，例如：this.form.patchValue(data, {emitEvent: false}).

按预期工作。

现在我有一些逻辑，当加载表单时，我将整个表单设置为禁用，this.form.disable({ emitEvent: false })，当加载完成后，它再次将整个表单设置为启用：this.form.disable({ emitEvent: false })

但我也有逻辑，根据不同的标志将 FormControl 设置为 enabled/disabled：this.formControl.enable( {emitEvent: false});

我现在看到的问题是，当 Form 更改状态时，它会触发 FormControl.valueChanges，即使我提供了 emitEvent: false 标志。

这是预期的行为还是错误？我期望在提供标志时根本不会触发任何事件？

我做了一个可以在这里测试的地方： https://plnkr.co/edit/RgyDItYtEfzlLVB6P5f3?p=preview

Answer 1

disable() 和 enable() 函数 (code source):

/**
 * Disables the control. This means the control will be exempt from validation checks and
 * excluded from the aggregate value of any parent. Its status is `DISABLED`.
 *
 * If the control has children, all children will be disabled to maintain the model.
 * @param {?=} opts
 * @return {?}
 */
AbstractControl.prototype.disable = function (opts) {
    if (opts === void 0) { opts = {}; }
    this._status = DISABLED;
    this._errors = null;
    this._forEachChild(function (control) { control.disable({ onlySelf: true }); });
    this._updateValue();
    if (opts.emitEvent !== false) {
        this._valueChanges.emit(this._value);
        this._statusChanges.emit(this._status);
    }
    this._updateAncestors(!!opts.onlySelf);
    this._onDisabledChange.forEach(function (changeFn) { return changeFn(true); });
};
/**
 * Enables the control. This means the control will be included in validation checks and
 * the aggregate value of its parent. Its status is re-calculated based on its value and
 * its validators.
 *
 * If the control has children, all children will be enabled.
 * @param {?=} opts
 * @return {?}
 */
AbstractControl.prototype.enable = function (opts) {
    if (opts === void 0) { opts = {}; }
    this._status = VALID;
    this._forEachChild(function (control) { control.enable({ onlySelf: true }); });
    this.updateValueAndValidity({ onlySelf: true, emitEvent: opts.emitEvent });
    this._updateAncestors(!!opts.onlySelf);
    this._onDisabledChange.forEach(function (changeFn) { return changeFn(false); });
};

已致电：

this._updateAncestors(!!opts.onlySelf);

它调用其父函数的 updateValueAndValidity() 函数而不带 emitEvent 标志，然后调用

this._valueChanges.emit(this._value);

这会触发表单的 valueChanges 发射器，您会在控制台中看到：

Form.valueChanges: Object { input2: null }

这是由表单触发的，而不是由 default 输入字段控制器触发的。为了停止祖先更新，我们只需要提供额外的标志 - onlySelf: true，它告诉只更新它自己而不是祖先。因此，在您不想更新祖先的 disable() 或 enable() 函数的每次调用中添加此标志：

disable(){
  this.form.disable({
    onlySelf: true, 
    emitEvent: false
  });
}

disableWEvent(){
  this.form.disable({
    onlySelf: true
  });
}

enable(){
  this.form.enable({
    onlySelf: true, 
    emitEvent: false
  });
}

enableWEvent(){
  this.form.enable({
    onlySelf: true
  });
}

disableCtrl(){
  this.formControl.disable({
    onlySelf: true, 
    emitEvent: false
  });
}

disableCtrlWEvent(){
  this.formControl.disable({
    onlySelf: true
  });
}

enableCtrl(){
  this.formControl.enable({
    onlySelf: true, 
    emitEvent: false
  });
}

enableCtrlWEvent(){
  this.formControl.enable({
    onlySelf: true
  });
}

这将解决叶窗体控件（没有子控件的控件）的问题，但是这一行

this._forEachChild(function (control) { control.disable({ onlySelf: true }); });

将调用 disable（或 enable）函数而不传递 emitEvent: false。它看起来像 angular 错误，因此，作为解决方法，我们可以重写这两个函数。首先导入 AbstractControl:

import {ReactiveFormsModule, FormBuilder, FormControl, Validators, AbstractControl} from '@angular/forms'

比覆盖两个函数：

// OVERRIDE disable and enable methods
// https://github.com/angular/angular/issues/12366
// https://github.com/angular/angular/blob/c59c390cdcd825cca67a422bc8738f7cd9ad42c5/packages/forms/src/model.ts#L318
AbstractControl.prototype.disable = function (opts) {
  if (opts === void 0) { opts = {}; }
  this._status = 'DISABLED';
  this._errors = null;
  this._forEachChild(function (control) { 
    control.disable(Object.assign(opts, {onlySelf: true})); 
  });
  this._updateValue();
  if (opts.emitEvent !== false) {
      this._valueChanges.emit(this._value);
      this._statusChanges.emit(this._status);
  }
  this._updateAncestors(!!opts.onlySelf);
  this._onDisabledChange.forEach(function (changeFn) { return changeFn(true); });
};
AbstractControl.prototype.enable = function (opts) {
  if (opts === void 0) { opts = {}; }
  this._status = 'VALID';
  this._forEachChild(function (control) { 
    control.enable(Object.assign(opts, {onlySelf: true})); 
  });
  this.updateValueAndValidity({ onlySelf: true, emitEvent: opts.emitEvent });
  this._updateAncestors(!!opts.onlySelf);
  this._onDisabledChange.forEach(function (changeFn) { return changeFn(false); });
};

更新的插件：https://plnkr.co/edit/IIaByz4GlBREj2X9EKvx?p=preview

FormControl 上的 ValueChanges 在 Form.enable 时触发，即使有 emitEvent: false

ValueChanges on FormControl triggers when Form.enable, even with emitEvent: false

angular

angular-reactive-forms