{"action":"created","issue":{"url":"https://api.github.com/repos/Polymer/polymer/issues/3280","labels_url":"https://api.github.com/repos/Polymer/polymer/issues/3280/labels{/name}","comments_url":"https://api.github.com/repos/Polymer/polymer/issues/3280/comments","events_url":"https://api.github.com/repos/Polymer/polymer/issues/3280/events","html_url":"https://github.com/Polymer/polymer/issues/3280","id":125505747,"number":3280,"title":"Array updates not observed, template value not recomputed.","user":{"login":"danostrowski","id":125086,"avatar_url":"https://avatars.githubusercontent.com/u/125086?v=3","gravatar_id":"","url":"https://api.github.com/users/danostrowski","html_url":"https://github.com/danostrowski","followers_url":"https://api.github.com/users/danostrowski/followers","following_url":"https://api.github.com/users/danostrowski/following{/other_user}","gists_url":"https://api.github.com/users/danostrowski/gists{/gist_id}","starred_url":"https://api.github.com/users/danostrowski/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/danostrowski/subscriptions","organizations_url":"https://api.github.com/users/danostrowski/orgs","repos_url":"https://api.github.com/users/danostrowski/repos","events_url":"https://api.github.com/users/danostrowski/events{/privacy}","received_events_url":"https://api.github.com/users/danostrowski/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":2,"created_at":"2016-01-07T23:08:00Z","updated_at":"2016-01-08T22:52:31Z","closed_at":null,"body":"This is possibly a duplicate, or related to, these two issues:\r\n\r\nhttps://github.com/Polymer/polymer/issues/3254\r\nhttps://github.com/Polymer/polymer/issues/3239\r\n\r\nI am trying to get a CSS value to be different based on whether an array has a length of 0 or >0. However, `this.push('path', val)` doesn't seem to notify or redraw the template when updating an array property.\r\n\r\nI've put together a couple fiddles showing this. The square SHOULD change to have the \"some\" class which would have a different background color. You can see in the logging that initially either the method (computed value) or the observer is called on first loading up... but then when the tap happens, neither are called.\r\n\r\nExample A, changing a variable when the notify goes off... https://jsfiddle.net/qez3thqr/\r\nExample B, slightly different, using a computed value... https://jsfiddle.net/19pfuwby/"},"comment":{"url":"https://api.github.com/repos/Polymer/polymer/issues/comments/170149801","html_url":"https://github.com/Polymer/polymer/issues/3280#issuecomment-170149801","issue_url":"https://api.github.com/repos/Polymer/polymer/issues/3280","id":170149801,"user":{"login":"danostrowski","id":125086,"avatar_url":"https://avatars.githubusercontent.com/u/125086?v=3","gravatar_id":"","url":"https://api.github.com/users/danostrowski","html_url":"https://github.com/danostrowski","followers_url":"https://api.github.com/users/danostrowski/followers","following_url":"https://api.github.com/users/danostrowski/following{/other_user}","gists_url":"https://api.github.com/users/danostrowski/gists{/gist_id}","starred_url":"https://api.github.com/users/danostrowski/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/danostrowski/subscriptions","organizations_url":"https://api.github.com/users/danostrowski/orgs","repos_url":"https://api.github.com/users/danostrowski/repos","events_url":"https://api.github.com/users/danostrowski/events{/privacy}","received_events_url":"https://api.github.com/users/danostrowski/received_events","type":"User","site_admin":false},"created_at":"2016-01-08T22:52:31Z","updated_at":"2016-01-08T22:52:31Z","body":"Hey Arthur, thanks for the reply.\r\n\r\nSo I went back. As you suggested, if you completely replace the array, a single observer on `history` works. If you use `history.length` and pass it to a method for the `on-tap` it works. Cool.\r\n\r\nHowever, what I found was that setting up an \"observers\" array looking at `history.splices` or `history.*` does *not* seem to work. The `historyChanged` observer doesn't seem to fire in either of the following scenarios.\r\n\r\nLooking at `history.splices` ... https://jsfiddle.net/ug3spghy/\r\nLooking at `history.*` ... https://jsfiddle.net/7avvzaxo/\r\n\r\nAm I seeing this correctly? I'm setting observers up like so:\r\n\r\n```\r\nobservers: [\r\n    'historyChanged(history.*)'\r\n],\r\n```\r\n\r\nShouldn't the observer function fire, here?"}}