DefaultsStorage

Use UserDefaults in AppKit and UIKit as easily as @AppStorage in SwiftUI, with simple reactivity via didSet, no Combine dependency required.

License

• Author: Terence J. Grant
• License: MIT License
• Donate: Your donations are appreciated!

About

@DefaultsStorage is a property wrapper that reflects a UserDefaults value, allowing reactive updates via didSet when values change.

This work-alike for @AppStorage reads from and writes to UserDefaults the same way, making migration to or from SwiftUI straightforward.

Features

• Simple property wrapper for storing and retrieving UserDefaults values.
• Supports Bool, Int, Double, String, Date, and Data.
  • Arrays of those types, for instance [Int]
  • Dictionaries of those types where the "key" is of type String, for instance [String: Int]
• Also supports URL and enums with String or Int raw values.
• Provides didSet-based reactivity.
• Compatible with values stored by @AppStorage.
• Fully tested for reliability.

Installation

Swift Package Manager (SPM)

Add DefaultsStorage to your project with Swift Package Manager in Xcode:

1. Go to "File -> Add Package Dependency…"
2. Enter the package URL: https://github.com/tatewake/DefaultsStorage
3. Use "Dependency Rule -> Exact Version" and set to use release version "1.1.0".

Usage

Simple Example

The @DefaultStorage tag will load from UserDefaults on instantiation and save automatically when the value changes. If no value exists in UserDefaults, the initializer will provide a default value.

@DefaultsStorage("name") var name = "User"

This syncs automatically on initialization or when modified in code.

Reactive Example

Here’s an example using SettingsModel as a struct to leverage didSet reactivity.

struct SettingsModel {
    struct Display: Equatable {
        enum Address: String {
            case first, multiple, last
        }

        @DefaultsStorage("addressSourcePublic") var addressSourcePublic = false
        @DefaultsStorage("addressToDisplay") var addressToDisplay = Address.multiple
    }

    struct Network: Equatable {
        @DefaultsStorage("offlineUpdateFrequency") var offlineUpdateFrequency = 30.0
        @DefaultsStorage("onlineUpdateFrequency") var onlineUpdateFrequency = 60.0
    }

    var display = Display()
    var network = Network()
}

Now, in a top-level Model class, we use didSet to handle changes in SettingsModel via a delegate:

class Model {
	weak var delegate: MyDelegate?

	var settings = SettingsModel() {
	    didSet {
	        if oldValue.display != settings.display {
	            delegate?.displaySettingsChanged(display: settings.display)
	        }

	        if oldValue.network != settings.network {
	            delegate?.networkSettingsChanged(network: settings.network)
	        }
	    }
	}
	...
}

This is just a simple example, but it shows the straightforward nature of DefaultsStorage.

Caveats

While @DefaultsStorage is similar to @AppStorage, there are two key differences:

1. External changes won’t update in real time, and
2. Properties sharing the same key won’t stay in sync.

This is because @DefaultsStorage only reads from UserDefaults on initialization, and only internal code changes trigger the didSet handler.

Therefore, if another app or process updates your UserDefaults store, or two @DefaultsStorage properties use the same key, these changes won’t trigger reactively.

The first scenario is rare, and for the second, ensure a single variable per setting as the “source of truth.”

Acknowledgements

• Inspired by SwiftUI's @AppStorage.