Swift uses userdefaults and codable to save an array of class objects or structure instances

swift use UserDefaults And Codable  Save an array of class objects or structure instances

        I wrote an article before 《swift use UserDefaults And NSSecureCoding Save an array of class objects 》 The article , Although it can save class and structure arrays , But in actual use, each class or structure to be saved should be encoded and decoded , There is also more code when saving and reading , It is complicated to use , Especially when saving and reading arrays are frequent .

        This article uses swift4.0  Agreement brought by Codable To solve the problems mentioned above .

        Codable It is based on the basic agreement  Encodable,Decodable,CodingKey  Above . The specific content will not be expanded . In this article, its use is very simple , Just inherit the protocol when defining classes and structures . The code is as follows ：

struct Item: Codable {
    var uuid: UUID
    var inAction: Int
    var outAction: Int
    var useful: Bool
}

        Just follow the above definition , Don't ask  《swift use UserDefaults And NSSecureCoding Save an array of class objects 》 Then write the coding and decoding code as in , Is it simple .

        To further simplify the code , Easy to use , Yes  UserDefaults Expand as follows

extension UserDefaults {
    //  Save the class array 
    func set<T:Encodable>(classArrory object: [T], key: String) {
        do {
            let data = try JSONEncoder().encode(object)
            self.set(data, forKey: key)
        } catch {
            print(error)
        }
    }
    
    //  Read the class array 
    func classArrory<T:Decodable>(forKey key : String) -> [T] {
        guard let data = self.data(forKey: key) else { return [] }
        do {
            return try JSONDecoder().decode([T].self, from: data)
        } catch {
            print(error)
        }
        return []
    }
}

         In the above code , function set The main function is to encode and save the structure array ,  function classArrory Its main function is to read structural data and decode , Template parameters are used in both functions T, To specify different classes and structures . There is nothing else to say , Very simple, at a glance .

        The foundation has been laid , Let's see how to use it

 let ud = UserDefaults.standard

 let item1 = Item(uuid: "00000023-0000-1000-8000-0026BB765291", inAction: 0, outAction: 1, useful: true)

 let item2 = Item(uuid: "0000003E-0000-1000-8000-0026BB765475", inAction: 1, outAction: 1, useful: true)

 var items = [item1, item2]

 //  Save the class array 
 ud.set(classArrory: items, key: "homekits")

 ...

 //  Read the class array 
 items = ud.classArrory(forKey: "homekits")

        After defining the array , Write... In one line , One line readout , Is it simple ？

        Related blogs

        《swift use UserDefaults And NSSecureCoding Save an array of class objects 》