Strange behaviour on panels [expanded]

[mackelito]

Maybe I´m just totally using this the wrong way but here we go :)

Bug, feature request, or proposal:

Bug

What is the expected behavior?

[expanded] function should run once

What is the current behavior?

it runs twice for each panel

What are the steps to reproduce?

open the console and click on the panels

Providing a Plunker (or similar) is the best way to get the team to see your issue.
Plunker template: https://goo.gl/DlHd6U
http://plnkr.co/edit/ckk4BCkNYNgNzJodW53t?p=preview

What is the use-case or motivation for changing an existing behavior?

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Is there anything else we should know?

[andrewseguin]

This is due to Angular running change detection twice on the template, unrelated to Material. http://plnkr.co/edit/inbSg6S7N5r6UPbVH0Ev?p=preview

[mackelito]

@andrewseguin just to be clear... is this a angular bug? Or should I have another approach?

[willshowell]

No bug, its just that angular's change detection must be very conservative in order to detect any changes that may have occurred in shouldBeExpanded().

See here that setting your AppComponent to OnPush will only run change detection once.

http://plnkr.co/edit/ah3Ji1C93nz5EwRcVEmi?p=preview

[mackelito]

aah.. I now see that it does not behave as I expected.. it expanded=true then it triggers the opened event.. will need to find another way then.. thx!

[mackelito]

Any suggestions btw? :D

[willshowell]

This seems to behave as expected with minimal reads of local storage:

http://plnkr.co/edit/Q3daXShLOilqhUA4J7eo?p=preview

I think the issue is that you were returning a string from shouldBeExpanded() instead of a boolean. Note that the string 'false' is truthy, whereas the boolean false is not.

[mackelito]

Never mind.. we´ll probably couple it to the router state instead! :) 👍

[mackelito]

@willshowell aaaaah.. of course! thx! :)

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