Migrating to 1.10

Update your code to make use of the new state sharing tools in the library, such as the Shared property wrapper, and the appStorage and fileStorage persistence strategies.

Overview

The Composable Architecture is under constant development, and we are always looking for ways to simplify the library, and make it more powerful. This version of the library only introduced new APIs and did not deprecate any existing APIs.

Important: Before following this migration guide be sure you have fully migrated to the newest tools of version 1.9. See doc:MigrationGuides for more information.

Sharing state

The new tools added are concerned with allowing one to seamlessly share state with many parts of an application that is easy to understand, and most importantly, testable. See the dedicated doc:SharingState article for more information on how to use these new tools.

To share state in one feature with another feature, simply use the Shared property wrapper:

@ObservableState
struct State {
  @Shared var signUpData: SignUpData
  // ...
}

This will require that SignUpData be passed in from the parent, and any changes made to this state will be instantly observed by all features holding onto it.

Further, there are persistence strategies one can employ in @Shared. For example, if you want any changes of signUpData to be automatically persisted to the file system you can use fileStorage(_:decoder:encoder:) and specify a URL:

@ObservableState
struct State {
  @Shared(.fileStorage(URL(/* ... */) var signUpData = SignUpData()
  // ...
}

Upon app launch the signUpData will be populated from disk, and any changes made to signUpData will automatically be persisted to disk. Further, if the disk version changes, all instances of signUpData in the application will automatically update.

There is another persistence strategy for storing simple data types in user defaults, called appStorage. It can refer to a value in user defaults by a string key:

@ObservableState 
struct State {
  @Shared(.appStorage("isOn")) var isOn = false
  // ...
}

Similar to fileStorage(_:decoder:encoder:), upon launch of the application the initial value of isOn will be populated from user defaults, and any change to isOn will be automatically persisted to user defaults. Further, if the user defaults value changes, all instances of isOn in the application will automatically update.

That is the basics of sharing data. Be sure to see the dedicated doc:SharingState article for more detailed information.