Swift Cache Service (leveraging Codable / JSON support) and simple implementation with UserDefaults

CacheService.swift

import Foundation

protocol CacheService {
    
    func load<T: Cachable>(_ identifier: String) throws -> T?
    
    func save<T: Cachable>(_ identifier: String, _ cachable: T) throws
    
    func clear<T: Cachable>(_ type: T.Type) throws
    func clear(_ identifier: String) throws
}

extension CacheService {
    
    func load<T: Cachable>(_ type: T.Type) throws -> T? {
        try load()
    }
    
    func load<T: Cachable>() throws -> T? {
        try load(.init(describing: T.self))
    }
    
    func save<T: Cachable>(_ cachable: T) throws {
        try save(String(describing: T.self), cachable)
    }
}

typealias Cachable = Codable

UserDefaultsCacheService.swift

import Foundation

class UserDefaultsCacheService : CacheService {
    
    func load<T: Cachable>(_ identifier: String) throws -> T? {
        do {
            return try UserDefaults
                .standard
                .data(forKey: identifier)
                .map(decode)
        } catch {
            return nil
        }
    }
    
    func save<T: Cachable>(_ identifier: String, _ cachable: T) throws {
        do {
            let data = try encode(cachable)
            UserDefaults
                .standard
                .setValue(data, forKey: identifier)
        } catch {
            throw error
        }
    }
    
    func clear<T: Cachable>(_ type: T.Type) throws {
        try clear(String(describing: T.self))
    }
    
    func clear(_ identifier: String) throws {
        UserDefaults
            .standard
            .removeObject(forKey: identifier)
    }
    
    fileprivate func decode<T: Decodable>(_ json: Data) throws -> T {
        try decoder.decode(T.self, from: json)
    }
    
    fileprivate func encode<T: Encodable>(_ value: T) throws -> Data {
        try encoder.encode(value)
    }
}

fileprivate let encoder: JSONEncoder = .init()
fileprivate let decoder: JSONDecoder = .init()