AEStoredWrapper

AEStoredWrapper.swift

/**
 *  https://gist.github.com/tadija/7668382ef3e14cb304b31b6273ae8f65
 *  Revision 2
 *  Copyright © 2021 Marko Tadić
 *  Licensed under the MIT license
 */

import Foundation

public struct AEStoredWrapper {
    public static var storage: UserDefaults = .standard
}

// MARK: - Wrappers

@propertyWrapper
public struct StoredValue<T> {
    public let key: String
    public let value: T
    public let storage: UserDefaults

    public var wrappedValue: T {
        get {
            storage.object(forKey: key) as? T ?? value
        }
        set {
            if let optional = newValue as? AnyOptional, optional.isNil {
                storage.removeObject(forKey: key)
            } else {
                storage.set(newValue, forKey: key)
            }
        }
    }

    public init(
        wrappedValue value: T,
        key: String,
        storage: UserDefaults = AEStoredWrapper.storage
    ) {
        self.value = value
        self.key = key
        self.storage = storage
    }
}

@propertyWrapper
public struct StoredRaw<T: RawRepresentable> {
    public let key: String
    public let value: T
    public let storage: UserDefaults

    public var wrappedValue: T {
        get {
            guard let object = storage.object(forKey: key) as? T.RawValue else {
                return value
            }
            return T(rawValue: object) ?? value
        }
        set {
            if let optional = newValue as? AnyOptional, optional.isNil {
                storage.removeObject(forKey: key)
            } else {
                storage.set(newValue.rawValue, forKey: key)
            }
        }
    }

    public init(
        wrappedValue value: T,
        key: String,
        storage: UserDefaults = AEStoredWrapper.storage
    ) {
        self.value = value
        self.key = key
        self.storage = storage
    }
}

@propertyWrapper
public struct StoredCodable<T: Codable> {
    public let key: String
    public let value: T
    public let storage: UserDefaults

    public var wrappedValue: T {
        get {
            guard let data = storage.object(forKey: key) as? Data else {
                return value
            }
            if let decoded = try? JSONDecoder().decode(T.self, from: data) {
                return decoded
            } else {
                assertionFailure("decoding failed for key: \(key)")
                return value
            }
        }
        set {
            if let optional = newValue as? AnyOptional, optional.isNil {
                storage.removeObject(forKey: key)
            } else {
                if let encoded = try? JSONEncoder().encode(newValue) {
                    storage.set(encoded, forKey: key)
                } else {
                    assertionFailure("encoding failed for key: \(key)")
                }
            }
        }
    }

    public init(
        wrappedValue value: T,
        key: String,
        storage: UserDefaults = AEStoredWrapper.storage
    ) {
        self.value = value
        self.key = key
        self.storage = storage
    }
}

// MARK: - Convenience

public extension StoredValue where T: ExpressibleByNilLiteral {
    init(key: String, storage: UserDefaults = AEStoredWrapper.storage) {
        self.init(wrappedValue: nil, key: key, storage: storage)
    }
}

public extension StoredRaw where T: ExpressibleByNilLiteral {
    init(key: String, storage: UserDefaults = AEStoredWrapper.storage) {
        self.init(wrappedValue: nil, key: key, storage: storage)
    }
}

public extension StoredCodable where T: ExpressibleByNilLiteral {
    init(key: String, storage: UserDefaults = AEStoredWrapper.storage) {
        self.init(wrappedValue: nil, key: key, storage: storage)
    }
}

// MARK: - Helpers

private protocol AnyOptional {
    var isNil: Bool { get }
}

extension Optional: AnyOptional {
    var isNil: Bool { self == nil }
}