State var change callback

[madeInLagny]

Hello, Thank you for your great work with lit-state. I am trying to catch a state var change call back to trigger some actions when a specific state var gets updated.

updated(changedProperties) {
  if (changedProperties.has('myState.collapsed')) {
doSomething()
  }
}

won't work because myState.collapsed is not a component property. What is the recommended method to catch that state var update callback ?

[christophe-g]

I would add an observer on connectedCallback in this case:

connectedCallback() {
  super.connectedCallback()
  myState.addObserver(() => {dothings}, ['collapsed'])
}

and remove the observer at disconnectedCallback

[madeInLagny]

Will do so. Thanks

[gitaarik]

That's the way indeed. Also documented here.