👀 Views: 85 💬 Answers: 1 📅 Created: 2025-06-13

typescript react type-assertion

I've hit a wall trying to I've been struggling with this for a few days now and could really use some help. I'm working on a TypeScript project using React (version 17) and I've encountered issues with type assertions on deeply nested properties. I've defined a type for my application's state as follows: ```typescript interface User { id: number; name: string; preferences: { theme: string; notifications: boolean; }; } interface AppState { users: User[]; currentUserId: number; } ``` In my component, I’m trying to access the `theme` property of the current user's preferences, and I use the following code: ```typescript const currentUser = appState.users.find(user => user.id === appState.currentUserId); const theme = (currentUser as User).preferences.theme; ``` However, I’m getting an behavior stating: ``` Property 'preferences' does not exist on type 'User | undefined'. ``` I thought using a type assertion would solve the scenario, but it seems TypeScript is still unsure if `currentUser` could be `undefined`. To handle this, I've tried adding a check before accessing `theme`: ```typescript if (currentUser) { const theme = currentUser.preferences.theme; } ``` This works but feels a bit cumbersome since I have to repeat the check in multiple places. Is there a more elegant way to handle this scenario? Perhaps with optional chaining or a different approach to type safety that would allow me to access deeply nested properties without excessive checks? Any best practices or design patterns you could recommend? My development environment is Ubuntu. Thanks in advance! I'm working with Typescript in a Docker container on Ubuntu 22.04. I'd love to hear your thoughts on this. I'm using Typescript stable in this project. Thanks in advance!