Switching resolve context
Syntax highlighting, as well as other code insight features like find usages, refactorings, code generation, and code analysis may depend on the set of preprocessor definitions which determine the rules of parsing and resolving your code. These rules are also known as resolve context.
Switch the current resolve context
From the run/debug configuration selector on the toolbar, select the desired run/debug configuration. The resolve context switches automatically following the selected configuration.
In the right bottom corner of the status bar, open the list of available resolve contexts and select the desired one:
Change resolve context indexing settings
By default, AppCode doesn't index all resolve contexts available for your project. You can choose the resolve contexts that should be indexed in Settings | Build, Execution, Deployment | Xcode. Here you can select SDKs and architectures for which indexing should be performed: