iphone: get User Defined variable in Target's setting by code?

问题

My project have multi-targets. Each target has its own Class file for setting stuff. I want to store that Class name in a target setting (Info.plist or Target's Building setting). So that I can define which class I need to use in each target based on this setting.

According to this question, I put "a target-specific User Defined variable" in each Target's Building Setting.

But don't know how to get it back in my code?

回答1:

As the Info.plist file is preprocessed too, you can use this approach:

Define a User defined setting in your build settings, for Example CLASS_NAME. And a key to your Info.plist-file. Name the key CLASS_NAME and set the value to ${CLASS_NAME}.

You can then access this setting by:

NSString* className = [[[NSBundle mainBundle] infoDictionary] valueForKey:@"CLASS_NAME"];

回答2:

You can not directly use a variable defined in the build settings. These variables are meant to be used by build tools.

Instead define a preprocessor macro in the Preprocessor Macros Variable like 'MYVAR=5'. You can access these macros in your code like:

#if MYVAR==5
    //Do something
#endif

Please note, that the evaluation of these expressions happens at build-time not at runtime.

It is very typical use to just define a Macro without caring for the value. For example define 'DEBUG=1' in the debug build settings and 'RELEASE=1' in the release build settings.

You can then test using #ifdef or #ifndef

#ifdef DEBUG
    // Log
#endif

来源：https://stackoverflow.com/questions/3316293/iphone-get-user-defined-variable-in-targets-setting-by-code