XCode has a number of built-in variables that are used for convenience in Build Settings, for example "$(PRODUCT_NAME)"
or "$(CURRENT_ARCH)"
.
Can I define my own variables? How / where?
In XCode 5 this has changed slightly.
Create a user-defined build setting. To create one in Xcode 4 select your project from the project navigator to open the project editor. Select your project or target from the left side of the editor. Click the Build Settings button at the top of the editor. Click the Add Build Setting button at the bottom of the editor and choose Add User-Defined Setting.
User-defined setting can be added in Xcode as specified below:
Xcode 4.x :
Select PROJECT / TARGETS -> “Add Build Setting” (option present in bottom-right corner of Xcode) -> “Add User-Defined Setting”
Xcode 5.x :
Select PROJECT / TARGETS -> Editor menu -> “Add Build Setting“ -> “Add User-Defined Setting”
This will add User-defined setting. Enter key-value for setting.