From UIKit to SwiftUI: a reproducible protocol and a priori typology for open-source iOS application migration

The coexistence of UIKit and SwiftUI has made iOS user-interface migration technically incremental but empirically difficult to classify. Prior repository research identifies several broad adoption trajectories, yet it does not distinguish replacement of existing functionality from greenfield addition, capability-specific adoption, stable coexistence, or UIKit fallback inside a SwiftUI-first application. This structured analytical review develops a reproducible protocol and an a priori, mechanism-oriented typology for a longitudinal multiple-case analysis of five production open-source iOS applications. The evidence base combines peer-reviewed software-engineering research, public Git histories and project documents, and official Apple interoperability documentation. The protocol defines a migration episode through integration direction, functional granularity, trigger, fate of UIKit artifacts, compatibility constraints, and associated test changes. It specifies monthly repository snapshots, SwiftSyntax and XML extraction, manual dual coding, agreement assessment, within-case timelines, cross-case synthesis, and sensitivity checks. The resulting analytical framework comprises six distinguishable configurations and a conditional matrix linking observable constraints to interoperability seams, candidate strategies, and scope-specific completion criteria. The framework treats SwiftUI growth without corresponding UIKit decline as adoption rather than replacement and uses a SwiftUI-first case with isolated UIKit bridges as a negative control. Because repository-wide extraction has not yet been executed, the article reports no project counts, effect estimates, or causal claims. Its contribution is therefore methodological and conceptual: it converts a broad technology transition into falsifiable classifications that can be evaluated on frozen, openly accessible repositories.