bug(mat-slide-toggle): calling public method toggle does not trigger change event

[jakobgruber]

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

Calling the public method toggle of the MatSlideToggle component does not trigger the change event.

Reproduction

StackBlitz link: https://stackblitz.com/edit/kgi2ifwx?file=src%2Fexample%2Fslide-toggle-overview-example.html,src%2Fexample%2Fslide-toggle-overview-example.ts&startScript=start
Steps to reproduce:

1. click on mat-slide-toggle -> change event is triggered and a log message is rendered
2. click on button which calls public method toggle -> no change event is triggered -> no log message is rendered

Expected Behavior

When I call the public method toggle I would expect, that not only the state is toggled but also the change event is triggered.

Actual Behavior

Only the state is toggled.

Environment

• Angular:
• CDK/Material:
• Browser(s):
• Operating System (e.g. Windows, macOS, Ubuntu):

[crisbeto]

The intent with the change event is that it's only for user-initiated changes. Since you're already calling the method manually, you know if it's going to change.

[jakobgruber]

Thanks for the response. I am surprised, that this behaviour is intented. The docs describes the change output with this sentence:

An event will be dispatched each time the slide-toggle changes its value.

When calling the public method toggle, the slide-toggle changes its value ^^

[marek-aguita]

Thanks for the response. I am surprised, that this behaviour is intented. The docs describes the change output with this sentence:

An event will be dispatched each time the slide-toggle changes its value.

When calling the public method toggle, the slide-toggle changes its value ^^

Exactly, it also makes me ask: what is the purpose of the toggle method if it only changes the UI, but not the data, and changing the data manually actually changes both UI and data?