Executing Angular bindings programmatically: A step-by-step guide

I have an Angular Material 5 component that contains an array of objects. This component displays a modal dialog which opens another component with a form to modify one object from the array.

After the dialog is closed, it sends back the modified object. The parent component then takes this result and updates the array. However, the display does not get updated, and this is my issue.

Do you think there's an error in my logic or do I need to manually re-trigger the binding? What would you recommend?

Below is the function responsible for opening the dialog and updating the array after it has been closed:

openDialog(event: any, id: number) {
     const index = this.contractors.findIndex(x => x.Id === id); 

     const dialogRef = this.dialog.open(ContractorEditComponent, {
     width: '600px',
     data: { contractor : this.contractors[index] }
   });

   dialogRef.afterClosed().subscribe((contractor: ContractorModel) => {
      if (contractor !== null) {
         this.contractors[index] = contractor; // update my collection with new value
         // Should I re-trigger data binding manually here to update the UI?
      }
   });
}

Answer №1

When working with Angular, it's important to note that the change detection mechanism will only be triggered when a new object reference is assigned, not when the existing object is modified. In the code snippet

this.contractors[index] = contractor
, you are only modifying the array itself without changing the reference.

To address this issue, there are various approaches you can take such as creating a fresh copy of the array, utilizing Observables, or manually initiating change detection by injecting and using ChangeDetectorRef:

constructor(private ref: ChangeDetectorRef) {}
// ...
this.ref.detectChanges();

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