How to create variables for use in Xcode build settings values?

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.

In XCode 5 this has changed slightly.

1. Select the project or target in the left side of the editor
2. Go to the Editor menu in the top menu bar
3. Select "Add Build Setting" and then "Add User-Defined Build Setting"

It's at the top of the build settings panel in Xcode 10.