Why do not you create different schemes and do not have separate configuration files,
Get your xcode -> your project -> information tab, as shown in the following screenshot

Click the plus button as shown in the image you will receive a popup asking

select "Duplicate Debug Configuration" and name it as "Stage".
Now go to your “TARGETS” → Select your application (DemoApp) → BuildSettings click the little plus sign in the upper right corner, as shown below.

and click "ADD OPERATING USER"
,
: BASE_URL,

"Staging" "Run → Info → Build Configuration", .

, .