Fixing SwiftUI's compiler is unable to type-check this expression in reasonable time Error

Learn how to resolve SwiftUI's common 'compiler is unable to type-check this expression in reasonable time' error by simplifying code, improving state initialization, and correctly passing data between views.
---
This video is based on the question https://stackoverflow.com/q/79468499/ asked by the user 'user29801994' ( https://stackoverflow.com/u/29801994/ ) and on the answer https://stackoverflow.com/a/79468502/ provided by the user 'workingdog support Ukraine' ( https://stackoverflow.com/u/11969817/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Getting The compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to drop me a comment under this video.
---
Understanding the Problem

When building SwiftUI apps, you may encounter an error like:

[[See Video to Reveal this Text or Code Snippet]]

This often happens with complex views or when Swift's type inference struggles, leading to compilation bottlenecks.

Key Causes in Your Code

Uninitialized or improperly initialized @ State variables.

Improper passing of data between views.

Nested NavigationStack usage without clear navigation paths.

How to Fix the Error

1. Initialize @ State Properties Properly

Swift requires explicit initialization of state variables.

Change this:

[[See Video to Reveal this Text or Code Snippet]]

to this:

[[See Video to Reveal this Text or Code Snippet]]

This removes ambiguity for the compiler.

2. Follow SwiftUI Naming Conventions

Start your View struct names with uppercase letters to adhere to Swift conventions — e.g., SearchResults instead of searchResults. This improves readability and consistency.

3. Pass Data Explicitly to Destination Views

If a view requires data, you must pass it directly when navigating.

Instead of:

[[See Video to Reveal this Text or Code Snippet]]

Use:

[[See Video to Reveal this Text or Code Snippet]]

This ensures that IndividualItemView receives the expected Review object.

4. Avoid Nesting NavigationStack

Nesting NavigationStack can confuse navigation state and increase compiler complexity. Instead:

Use a single NavigationStack at the app or main view level.

Manage navigation paths using NavigationPath or state variables.

This also helps keep your navigation logic clear and manageable.

Summary

To fix the "unable to type-check" error:

Always initialize @ State variables.

Pass all required data explicitly when creating destination views.

Avoid unnecessary or nested NavigationStack declarations.

Use consistent Swift naming conventions.

These steps help Swift’s compiler handle your views efficiently and eliminate vague type-checking errors.

Final Thoughts

Compiler errors about type-checking times are often due to overly complex or unclear SwiftUI view structures. Simplifying state management and navigation flow usually resolves them.

Apply these changes incrementally and test on a real device rather than just the preview to catch issues early.



Happy coding with SwiftUI!