Release Build Configuration as Release Fails Preview

Question

Tomato OP

Created Mar ’25

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I have a simple SwiftUI project with two basic build configurations (Debug, Release) as shown below.

I now choose Build > Scheme > Edit Scheme under Product and select Release as the current build configuration as shown below.

And the Preview canvas exhibit errors.

If I click on the Diagnostics button, it says under PREVIEW UPDATE ERROR

OptimizationLevelError: not building -Onone ”BuildSchemeCrazyDaughter.app” needs -Onone Swift optimization level to use previews (current setting is -O)

What does that mean and why don't I get the preview for the Release build configuration? Thanks.

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Answer 1

Tomato OP

Mar ’25

I guess I know what

needs -Onone Swift optimization level to use previews

means.

I need to select No Optimization [-Onone] under Swift Compiler -Code Generation in Build Settings. Yet, it doesn't resolve the preview issue.

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