When I pop back to that screen, the new item is not showing. In my render I have, on a detail screen I create a new item and add to the MyStore.items array. I've been banging my head against this for quite some time. Thanks for your help though, I really appreciate your time! Please create a small sample application preferably using codesandbox.io. privacy statement. By clicking “Sign up for GitHub”, you agree to our terms of service and When using computed values there are a couple of best practices to follow: Tip: computed values will be suspended if they are not observed. To help illustrate the point of computed values, the example below relies on autorun from the Reactions {} advanced section. — The header with the value "initial" is from the Datastore.js file, and its value is set on the button click of the Login.js page. Once running click the login button and you will see the main dashboard page. Besides that they are highly optimized, so use them wherever possible. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Use makeObservable to declare a getter as computed. Take the below example of a React component that renders a specific Item, and the application supports multi-selection.. How can we implement a derivation like store.isSelected(item.id)?. They evaluate lazily, caching their output and only recomputing if one of the underlying observables has changed. they're used to log you in. (Btw, I deliberately didn't make the downloadStatus field observable, because it also has intermediary status flags that are of no interest to the component and shouldn't trigger rendering.). The philosophy and benefits of the mental model provided by MobX are also described in great detail in the blog posts UI as an afterthought and How to decouple state and UI (a.k.a. https://mobx.js.org/refguide/computed-decorator.html. Sign in thanks. computed usually behaves the way you want it to out of the box, but it's possible to customize its behavior by passing in an options argument. Note that computed properties are not enumerable. I am experiencing the same problem, and is interested what the solution was. For more information, see our Privacy Statement. @observer makes your component react to any observable you use in render(). You signed in with another tab or window. Modifying an observable array does not update the view via the , Here is an example where clicking the "Add item" button does not add any new li to the rendered ul . Note that in that class that declares that computed field, the downloadStatus field is not observed, while cacheFile is. This behavior is correct and downloadStatus should be observable as the output value of fileUri depends on it. (Let me know if you cant run, this is the first time i've posted and shared on github).