--- title: The hidden cost of unstable SwiftUI environment defaults description: Xcode 27 introduces a warning when a SwiftUI `@Entry` macro declaration creates a new class instance as its default value. Because class instances are compared... canonical: https://daily.dev/posts/the-hidden-cost-of-unstable-swiftui-environment-defaults-l5v6v64bo twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: The hidden cost of unstable SwiftUI environment defaults | daily.dev og:description: Xcode 27 introduces a warning when a SwiftUI `@Entry` macro declaration creates a new class instance as its default value. Because class instances are compared... og:url: https://daily.dev/posts/the-hidden-cost-of-unstable-swiftui-environment-defaults-l5v6v64bo og:image: https://api.daily.dev/og/posts/L5V6V64Bo.png og:image:alt: The hidden cost of unstable SwiftUI environment defaults og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # The hidden cost of unstable SwiftUI environment defaults **[Nil Coalescing](https://daily.dev/sources/nilcoalescing)** · 5 min read · 0 upvotes · 0 comments ## Summary Xcode 27 introduces a warning when a SwiftUI `@Entry` macro declaration creates a new class instance as its default value. Because class instances are compared by reference identity, every fallback access to the environment value returns a different reference, causing SwiftUI to treat the value as changed and unnecessarily re-evaluate views that read it. The fix is to create the default instance outside the `@Entry` declaration in stable storage (e.g., a module-level `let`) so every fallback access returns the same reference. Alternatively, the environment value can be made optional and always injected explicitly, avoiding a fallback entirely. The issue also applies to other unstable expressions like `Date()` or `UUID()`, not just class types. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Issue \#82: Why Your Views Re-Run, Deadlines in Review, SwiftData Behind a Wall](https://daily.dev/posts/issue-82-why-your-views-re-run-deadlines-in-review-swiftdata-behind-a-wall-nz1iu9ibh) · iOS Code Review · 0 upvotes · 0 comments - [SwiftUI data dependencies and their effect on view updates](https://daily.dev/posts/swiftui-data-dependencies-and-their-effect-on-view-updates-2kp42i6if) · Nil Coalescing · 1 upvotes · 0 comments - [Introducing @DependencyEntry](https://daily.dev/posts/introducing-dependencyentry-qtbe80zmm) · Point-Free Pointers · 3 upvotes · 0 comments --- Tags: [#performance](https://daily.dev/tags/performance), [#swift](https://daily.dev/tags/swift), [#swiftui](https://daily.dev/tags/swiftui), [#xcode](https://daily.dev/tags/xcode) [View this post on daily.dev](https://daily.dev/posts/the-hidden-cost-of-unstable-swiftui-environment-defaults-l5v6v64bo) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"The hidden cost of unstable SwiftUI environment defaults","url":"https://daily.dev/posts/the-hidden-cost-of-unstable-swiftui-environment-defaults-l5v6v64bo","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/the-hidden-cost-of-unstable-swiftui-environment-defaults-l5v6v64bo"},"datePublished":"2026-08-02T07:15:03.020Z","dateModified":"2026-08-02T07:32:32.235Z","description":"Xcode 27 introduces a warning when a SwiftUI `@Entry` macro declaration creates a new class instance as its default value. 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