Moving the scope of the declared dependency changes outcome unexpectedly.

[nashysolutions]

I appreciate the single entry point system and how dependencies can be scoped, but this still seems like a trap. Should we declare dependencies at the highest scope in a view, to be safe?

struct ContentView: View {
    
    @Dependency(\.mainBundleClient) var mainBundle
   
    var body: some View {
        VStack(spacing: 40) {
            
            Text("Version: " + extractVersion())
            
            withDependencies {
                $0.mainBundleClient = .mock(
                    extractShortVersionString: {
                        SemanticVersion(major: 9, minor: 9, patch: 9)
                    }
                )
            } operation: {
                AnotherView()
            }
        }
        .padding()
    }
    
    func extractVersion() -> String {
        do {
            let value: SemanticVersion = try mainBundle.extractShortVersionString()
            return value.description
        } catch {
            return error.localizedDescription
        }
    }
}

struct AnotherView: View {
    
    @Dependency(\.mainBundleClient) var mainBundle
        
    var body: some View {
        Text("Scoped Version: " + extractVersion())
    }
    
    func extractVersion() -> String {
        do {
            let value: SemanticVersion = try mainBundle.extractShortVersionString()
            return value.description
        } catch {
            return error.localizedDescription
        }
    }
}

If I make this change, the outcome is unexpected at runtime.

struct AnotherView: View {
      
    var body: some View {
        Text("Scoped Version: " + extractVersion())
    }
    
    func extractVersion() -> String {
        @Dependency(\.mainBundleClient) var mainBundle // here instead
        do {
            let value: SemanticVersion = try mainBundle.extractShortVersionString()
            return value.description
        } catch {
            return error.localizedDescription
        }
    }
}

[mbrandonw]

Hi @nashysolutions, dependencies are not meant to be used in views. SwiftUI does not open up enough of the internals of views to allow something like withDependencies to override a value for a particular part of a view hierarchy. And this goes for all @TaskLocals, not just our dependencies library.

We've also never stated that dependencies should be used in views. Is there a reason you are not using @Environment for this?

Also, this discussion seems almost identical to #369. Perhaps you can close that one and focus the conversation in just this one?

[nashysolutions]

I was under the impression it could be used anywhere. If it should not be used in a view like this then no problem. I'll just go ahead and not do that.