How to Remove Components, Form Elements, and Items using NgIf in Angular?

Question

How to Remove Components, Form Elements, and Items using NgIf in Angular?

Is there a way to remove DOM elements and Components using *NgIf or any Ng function?

I am working with a dropdown list that displays different forms based on the selection. The issue arises when a user changes the dropdown option, returns to the original option, and finds that the previous form data still exists instead of being cleared.

What would be the most effective method to delete all forms, variables, and the component itself when the dropdown selection changes?

Refer to the code snippet below,

<div class = "addressformtotal">
    <div class = "addressblock">
        <app-address-formatheader-form></app-address-formatheader-form>
        <div *ngIf="formatMessage?.addressFormatDescription.includes('Standard')"><app-address-mailing-standard-form></app-address-mailing-standard-form></div>
        <div *ngIf="formatMessage?.addressFormatDescription.includes('Military')"><app-address-mailing-military-form></app-address-mailing-military-form></div>
        <div *ngIf="formatMessage?.addressFormatDescription.includes('Post')"><app-address-mailing-pobox-form></app-address-mailing-pobox-form></div>
        <div *ngIf="formatMessage?.addressFormatDescription.includes('Free')"><app-address-free-form></app-address-free-form></div>
        <div *ngIf="formatMessage?.addressFormatDescription.includes('Rural')"><app-address-mailing-rural-form></app-address-mailing-rural-form></div>
        <div *ngIf="formatMessage?.addressFormatDescription.includes('International')"><app-address-mailing-international-form></app-address-mailing-international-form></div>
    </div>

javascript css angular typescript angular8

Answer 1

Answer №1

In my opinion, the inner components (app-address-mailing-standard-form, app-address-mailing-military-form...) could benefit from having an @Input for formGroup and *ngIf directives.

@Input()group:FormGroup

<form *ngIf="group" [formGroup]="group">
    <input formControlName="prop1">
     ...
</form>

Therefore, your main.app could look like this:

<app-address-formatheader-form 
         [group]="form.get("header")>
</app-address-formatheader-form>
<app-address-mailing-standard-form 
         [group]="form.get('mailing')">
</app-address-mailing-standard-form>
<app-address-mailing-standard-form 
         [group]="form.get('military')">
</app-address-mailing-standard-form>
...

If you create the form in your main.app as shown below:

this.form=new FormGroup({
   header:new FormGroup({...}),
   military:new FormGroup({...})
})

Only "header" and "military" will be displayed, but this is just a suggestion. It all depends on how and where you create the form and formGroup.

If you create the formGroup within the components, you can use a setter in the input like this:

@Input() set visible(value)
{
    if (visible)
       this.group=new formGroup({...})
}

And pass only the "visible" argument:

<app-address-formatheader-form [visible]="variable"></app-address-formatheader-form>

Once again, the form should include:

<form *ngIf="group" [formGroup]="group">
    <input formControlName="prop1">
     ...
</form>

Answer 2

In my opinion, the inner components (app-address-mailing-standard-form, app-address-mailing-military-form...) could benefit from having an @Input for formGroup and *ngIf directives.

@Input()group:FormGroup

<form *ngIf="group" [formGroup]="group">
    <input formControlName="prop1">
     ...
</form>

Therefore, your main.app could look like this:

<app-address-formatheader-form 
         [group]="form.get("header")>
</app-address-formatheader-form>
<app-address-mailing-standard-form 
         [group]="form.get('mailing')">
</app-address-mailing-standard-form>
<app-address-mailing-standard-form 
         [group]="form.get('military')">
</app-address-mailing-standard-form>
...

If you create the form in your main.app as shown below:

this.form=new FormGroup({
   header:new FormGroup({...}),
   military:new FormGroup({...})
})

Only "header" and "military" will be displayed, but this is just a suggestion. It all depends on how and where you create the form and formGroup.

If you create the formGroup within the components, you can use a setter in the input like this:

@Input() set visible(value)
{
    if (visible)
       this.group=new formGroup({...})
}

And pass only the "visible" argument:

<app-address-formatheader-form [visible]="variable"></app-address-formatheader-form>

Once again, the form should include:

<form *ngIf="group" [formGroup]="group">
    <input formControlName="prop1">
     ...
</form>

Answer 3

Answer №2

One approach is to utilize reactive forms for the ability to reset a form easily. This method does not involve two-way binding, allowing for better control over your data.

When there is a change in the dropdown selection, ngIf can be used to generate a new reactive form with no pre-existing data.

To learn more about creating reactive forms, visit this link.

From my understanding, the issue may arise from binding data shared between components (parent-child) causing changes through two-way binding without effecting any actual alterations.

Answer 4

One approach is to utilize reactive forms for the ability to reset a form easily. This method does not involve two-way binding, allowing for better control over your data.

When there is a change in the dropdown selection, ngIf can be used to generate a new reactive form with no pre-existing data.

To learn more about creating reactive forms, visit this link.

From my understanding, the issue may arise from binding data shared between components (parent-child) causing changes through two-way binding without effecting any actual alterations.

How to Remove Components, Form Elements, and Items using NgIf in Angular?

Answer №1

Answer №2

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