How do you manage state and storage in Ionic apps using lifecycle methods?

2 Why are they important for Ionic apps?

Ionic apps are based on web components, which are reusable and independent UI elements that can be added or removed from the DOM dynamically. Web components have their own lifecycle events, such as connectedCallback, disconnectedCallback, or attributeChangedCallback. Ionic integrates these events with Angular's lifecycle methods, so you can leverage both frameworks to manage your app's state and storage. For example, you can use ngOnInit to load data from local storage, ngAfterViewInit to update the UI based on the data, and ngOnDestroy to save data to local storage before the component is destroyed.

3 How do you use them for state and storage?

To use lifecycle methods for state and storage, you must adhere to certain best practices and common patterns. For instance, ngOnInit is used to initialize your component or page state and load data from local or remote sources - this method is only called once when the component or page is first created, making it ideal for setting up initial values and fetching data that does not change frequently. ngAfterViewInit, on the other hand, is used to update your view based on the data loaded in ngOnInit - this method is called after the view and its children are initialized, so it can be utilized to manipulate the DOM, bind events, or apply animations. Ionic-specific methods ionViewWillEnter and ionViewDidEnter are used for actions that depend on the component or page being active or visible; conversely, ionViewWillLeave and ionViewDidLeave are used for actions that depend on the component or page being inactive or hidden. Finally, ngOnDestroy should be used to clean up any resources or subscriptions that were created in the previous methods - this method is called when the component or page is destroyed, either by navigation or by garbage collection.

4 What are some challenges and solutions?

Using lifecycle methods for state and storage can also pose some challenges and require solutions. For instance, Ionic Storage can be injected as a service to persist data across views and sessions. Additionally, Angular Services can be injected as dependencies to synchronize data between components or pages, using RxJS Observables. Furthermore, Angular Change Detection Strategies can be set as properties in the component or page class to optimize performance and memory usage. This involves choosing between Default or OnPush, in which Default means that Angular checks for changes every time an event occurs, and OnPush means that Angular checks for changes only when an input property changes or when a manual change detection is triggered.

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?