Shared User Defaults in iOS

Enable App Groups for both targets

With the NSUserDefaults class, you can save settings and properties related to application or user data.

While developing extensions in iOS, you may find a need to share application or user data between the host app and the extension.

To do so, you can enable the `App Groups` Capability.

1. In Xcode’s Project Navigator, Click the `Project Icon`
2. Select the `Host App` Target
3. Select the `Capabilities` Tab on the top menu
4. Toggle the `App Groups` capability
   - If you have not associated a development team you will be prompted to.
5. Select `+` icon and enter a unique group name such as `group.reverse.company.uri.name`
6. Repeat the above for the Extension’s target

You can then use NSUserDefaults initWithSuiteName:.

NSUserDefaults *sharedDefaults = [[NSUserDefaults alloc] initWithSuiteName:@"group.com.example.app"];

Then set a value in one target…

[sharedDefaults setObject:value forKey:@"key"];
[sharedDefaults synchronize];

And read the associated value in the other target…

NSString *value = [sharedDefaults stringForKey:@"key"];