Change user-defined variable from fastlane - xcode

Question

I have a user-defined variable in my Xcode project - MY_VARIABLE:
I linked MY_VARIABLE also in my .plist file:
And then I use it in my code:
NSString *myVariable = [[NSBundle mainBundle] objectForInfoDictionaryKey:#"MY_VARIABLE"];
In the fastfile I have my AppStore lane and, only in that case, I would like to change the value of MY_VARIABLE.
I'm currently using:
ENV["MY_VARIABLE"] = "appStoreValue"
but this doesn't work.

Answer 1

After a bit of research I found a solution to this.
I'm using xcargs in the gym action, like:
gym(
scheme: "MyScheme",
configuration: "Release",
use_legacy_build_api: 1,
xcargs: "MY_VARIABLE=appStoreValue"
)

Answer 2

Thx to https://stackoverflow.com/a/56179405/5790492 and https://nshipster.com/xcconfig/
I've created the xcconfig file, added it to project in Info tab. For fastlane added this plugin to work with xcconfig. And now it looks like:
def bumpMinorVersionNumber
currentVersion = get_xcconfig_value(path: 'fastlane/VersionsConfig.xcconfig',
name: 'FC_VERSION')
versionArray = currentVersion.split(".").map(&:to_i)
versionArray[2] = (versionArray[2] || 0) + 1
newVersion = versionArray.join(".")
update_xcconfig_value(path: 'fastlane/VersionsConfig.xcconfig',
name: 'FC_VERSION',
value: newVersion.to_s)
UI.important("Old version: #{currentVersion}. Version bumped to: #{newVersion}")
end
def bumpBuildNumber
currentBuildNumber = get_xcconfig_value(path: 'fastlane/VersionsConfig.xcconfig',
name: 'FC_BUILD')
newBuildNumber = currentBuildNumber.to_i + 1
update_xcconfig_value(path: 'fastlane/VersionsConfig.xcconfig',
name: 'FC_BUILD',
value: newBuildNumber.to_s)
UI.important("Old build number: #{currentBuildNumber}. Build number bumped to: #{newBuildNumber}")
end