如何识别FormArray中的哪个项目发出了valueChanges事件? [英] How to identify which item in FormArray emitted valueChanges event?
问题描述
在Angular
中,是否有办法识别动态 FormArray
中的哪个FormGroup
/FormControl
发出了valueChanges
事件?
In Angular
, is there a way to identify which FormGroup
/FormControl
in a dynamicFormArray
emitted the valueChanges
event?
我的FormArray
是动态的.它开始是空的,用户可以通过单击按钮将FormGroup
添加到FormArray
.
My FormArray
is dynamic. It starts out empty and users could add a FormGroup
to the FormArray
by clicking a button.
当valueChanges时,我需要重新验证控件.由于我不知道哪个控件发出了该事件,因此即使只有一个控件发生更改,我也会遍历整个FormArray
并验证所有FormGroup
/FormControl
-这是每次数组中的任何内容发生更改时.我该如何避免这样做?
When valueChanges, I need to re-validate the control. Since I dont know which control emitted the event, I loop through the entire FormArray
and validate all FormGroup
/FormControl
even though only one control changed - and this is every time when anything in the array changes. How can I avoid doing this?
this.myFormArray
.valueChanges
.subscribe(data => this.onValueChanged(data));
onValueChanged(data?: any): void {
// the data I receive is an entire form array.
// how can I tell which particular item emitted the event,
// so I don’t need to loop through entire array and run validation for all items.
for (let control in this.myFormArray.controls) {
// run validation on each control.
}
}
推荐答案
我通过在formGroup
中添加formControl
(名为groupIndex)来跟踪索引并在formGroup
级别而不是formArray
级别.在valueChanges
事件上,然后我可以访问存储当前索引的formControl
.
I resolved this issue by adding a formControl
(named groupIndex) in the formGroup
to track the index and subscribing to the valueChanges
at the formGroup
level instead of formArray
level. On valueChanges
event, I could then access the formControl
that stored the current index.
this.myMainFormGroup = this.myFormBuilder.group({
// other formControls
myFormArray: this.myFormBuilder.array([this.addArrayItem()])
});
// this method will be called every time the add button is clicked
addArrayItem(): FormGroup {
const itemToAdd = this.myFormBuilder.group({
// dont forget add input control for groupIndex in html for this. It will give error otherwise.
// i made the input control hidden and readonly
groupIndex:"",
firstName:["", [validator1, validator2]]
//other formControls
});
const myFormArray = <FormArray>this.myMainForm.get("myFormArray");
//set groupIndex
itemToAdd.get("groupIndex").patchValue(myFormArray.length -1);
//subscribe to valueChanges
itemToAdd.valueChanges
.debounceTime(200)
.subscribe(data => this.onValueChanged(data));
myFormArray.push(itemToAdd);
}
onValueChanged(data?: any): void {
const groupIndex = data["groupIndex"];
const myChangedGroup = <FormArray>this.myMainForm.get("myFormArray").controls[groupIndex];
// now I have hold of the group that changed without having to iterate through the entire array.
// run through the custom validator
this.generalValidator(myChangedGroup);
}
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