iOS Dev Recipes
RSS FeedQuick Look: How to access environment variables and launch options
For in depth information, but not as much reference material, see the Runtime Configuration Guide Apple provides.
For help with understanding where these go and how to use them, consider this excellent article at NSHipster.
Environment Variables:
Misc. Built-in Environment Variables
| Variable | Value(s) | Usage |
|---|---|---|
CFNETWORK_DIAGNOSTICS=3 |
0,1,2,3 | 0: Off, 3: Most Verbose - Use with caution, may leak SSL data on your simulator/device |
DYLD_PRINT_STATISTICS=1 |
More options documented here | |
OS_ACTIVITY_MODE=disable |
info, debug, disable | Sets the logging mode of the launched process to the specified level. See man log for more details. |
OBJC_HELP |
Dumps out a list (during app launch) of other environment variables that vary depending on OS version |
Objective-C
NSDictionary* environment = [[NSProcessInfo processInfo] environment];
environment[@"MY_ENV_VAR"];Swift
let environment = ProcessInfo.processInfo().environment
environment["MY_ENV_VAR"];Launch Options:
CoreData Options
| Launch Option | Values | Usage |
|---|---|---|
| -com.apple.CoreData.SQLDebug | 1,2,3 | Increasingly verbose log levels for SQL generated by CoreData |
| -com.apple.CoreData.SyntaxColoredLogging | YES, NO | Make CoreData logging colorful |
| -com.apple.CoreData.MigrationDebug | YES, NO | Enables additional logging for CoreData migrations |
| -com.apple.CoreData.ConcurrencyDebug 1 | 1 | Enables concurrency checks for NSManagedObject contexts - crash if used on an incorrect thread |
| -com.apple.CoreData.SQLiteIntegrityCheck | 1 | Run an SQLite integrity check on initialization |
Debugging Localization
| Launch Option | Values | Usage |
|---|---|---|
| -AppleLocale | Any locale identifier (e.g. 'en', 'it', 'es') | Force the locale on app launch |
| -NSDoubleLocalizedStrings | YES, NO | Doubles the length of all localized strings, e.g. "Word" => "Word Word" to debug layout issues |
| -NSShowNonLocalizedStrings | YES, NO | Shows non-localized strings in ALL CAPS so they're easier to spot |
| -NSForceRightToLeftWritingDirection | YES, NO | YES to force right-to-left mode to engage (even in non-RTL languages) |
Layout and State Restoration
| Launch Option | Values | Usage |
|---|---|---|
| -UIViewLayoutFeedbackLoopDebuggingThreshold | number of iterations to consider a loop | Enables the Layout Feedback Loop Debugger, and sets the time threshold that triggers it |
| -UIStateRestorationDebugLogging | YES, NO | Enables state restoration debug logging for debugging issues with application state restoring |
| -UIStateRestorationDeveloperMode | YES, NO | Keeps the state restoration info even if the app crashes |
Swift:
# If you want to handle parsing the options on your own:
ProcessInfo.processInfo().arguments // [String]
# The "Arguments" domain in user defaults overrides others, so just grab the value from UserDefaults
UserDefaults.standard