ios 将自定义类对象转换为 NSData

Converting custom class object into NSData

提问by Tamarisk

I have a custom class that I want to save into NSUserDefaults. I am told that I need to convert the class object into data in order to save it to NSUserDefaults. I found a lot of discrete string or ints to NSDataexamples but nothing on custom class to NSData. I know very little about the intricacies of NSDataencoding etc. Any help is appreciated

我有一个自定义类要保存到NSUserDefaults. 有人告诉我，我需要将类对象转换为数据才能将其保存到NSUserDefaults. 我在NSData示例中发现了很多离散字符串或整数，但在自定义类 to NSData. 我对NSData编码等的复杂性知之甚少。感谢任何帮助

EDIT: While I understand there are similar answers here, none of them are in Swift. Translating between the languages is doable, but it is extremely tedious and sometimes very counter-intuitive.

编辑：虽然我知道这里有类似的答案，但没有一个在 Swift 中。语言之间的翻译是可行的，但它非常乏味，有时非常违反直觉。

回答by Dharmesh Kheni

Here is one simple example for you:

这是一个简单的例子：

//Custom class.
class Person: NSObject, NSCoding {
    var name: String!
    var age: Int!
    required convenience init(coder decoder: NSCoder) {
        self.init()
        self.name = decoder.decodeObjectForKey("name") as! String
        self.age = decoder.decodeObjectForKey("age") as! Int
    }
    convenience init(name: String, age: Int) {
        self.init()
        self.name = name
        self.age = age
    }
    func encodeWithCoder(coder: NSCoder) {
        if let name = name { coder.encodeObject(name, forKey: "name") }
        if let age = age { coder.encodeObject(age, forKey: "age") }

    }
}

//create an instance of your custom class.
var newPerson = [Person]()

//add some values into custom class.
newPerson.append(Person(name: "Leo", age: 45))
newPerson.append(Person(name: "Dharmesh", age: 25))

//store you class object into NSUserDefaults.
let personData = NSKeyedArchiver.archivedDataWithRootObject(newPerson)
NSUserDefaults().setObject(personData, forKey: "personData")


//get your object from NSUserDefaults.
if let loadedData = NSUserDefaults().dataForKey("personData") {

    if let loadedPerson = NSKeyedUnarchiver.unarchiveObjectWithData(loadedData) as? [Person] {
        loadedPerson[0].name   //"Leo"
        loadedPerson[0].age    //45
    }
}

Tested with playground.

用操场测试。

Hope this helps.

希望这可以帮助。

回答by George

This following sample code is based on Richie Rich's answer (see above) and passes tests in this environment:

以下示例代码基于 Richie Rich 的回答（见上文）并在此环境中通过了测试：

• Xcode version 9.1 (9B55)
• Swift version 4.0.2 (swiftlang-900.0.69.2 clang-900.0.38, Target: x86_64-apple-macosx10.9)
• MacBook Air (11-inch, Mid 2012) with macOS High Sierra (version 10.13.1)

• Xcode version 9.1 (9B55)
• Swift version 4.0.2 (swiftlang-900.0.69.2 clang-900.0.38, Target: x86_64-apple-macosx10.9)
• MacBook Air (11-inch, Mid 2012) with macOS High Sierra (version 10.13.1)

---

---

// Foundation is required to NSObject and NSCoding
import Foundation

// A custom class called Person with two properties (a string name and an
// integer age), that is a subclass of NSObject and adopts NSCoding protocol.
class Person: NSObject, NSCoding {
  var name: String!
  var age: Int!

  // The convenience initializer for class Person
  // Reference
  // https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Initialization.html#//apple_ref/doc/uid/TP40014097-CH18-ID217
  convenience init(name: String, age: Int) {
    // self.init() is the designated initializer for class Person.
    // Reference
    // https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Initialization.html#//apple_ref/doc/uid/TP40014097-CH18-ID219
    self.init()
    self.name = name
    self.age = age
  }

  // The initializer init(coder:) is required by NSCoding protocol
  // Reference
  // https://developer.apple.com/documentation/foundation/nscoding
  // https://developer.apple.com/documentation/foundation/nscoding/1416145-init
  required convenience init(coder aDecoder: NSCoder) {
    self.init()
    // as! is a type casting operator
    // Reference
    // https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Expressions.html#//apple_ref/doc/uid/TP40014097-CH32-ID388
    self.name = aDecoder.decodeObject(forKey: "name") as! String
    self.age = aDecoder.decodeInteger(forKey: "age")
  }

  // The instance method encode(with:) is required by NSCoding protocol
  // Reference
  // https://developer.apple.com/documentation/foundation/nscoding
  // https://developer.apple.com/documentation/foundation/nscoding/1413933-encode
  func encode(with anEncoder: NSCoder) {
    if let name = name {
      anEncoder.encode(name, forKey: "name")
    }
    if let age = age {
      anEncoder.encode(age, forKey: "age")
    }
  }
}

// Create an array (or, generally speaking, a collection) as a container to
// hold instances of our custom class type Person.
// Reference
// https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/CollectionTypes.html
var anArrayOfPersons = [Person]()
print(anArrayOfPersons.count) // 0

// Add two instances into anArrayOfPersons.
// Reference
// https://developer.apple.com/documentation/swift/array
// https://developer.apple.com/documentation/swift/array/1538872-append
anArrayOfPersons.append(Person(name: "Cong", age: 33))
anArrayOfPersons.append(Person(name: "Sunny", age: 2))

// Archive anArrayOfPersons into NSData using NSKeyedArchiver.
// Reference
// https://developer.apple.com/documentation/foundation/nskeyedarchiver
// https://developer.apple.com/documentation/foundation/nskeyedarchiver/1413189-archiveddata
let dataToSave = NSKeyedArchiver.archivedData(withRootObject: anArrayOfPersons)

// Persist data. Storing anArrayOfPersons into UserDefaults as data.
// Reference
// https://developer.apple.com/documentation/foundation/userdefaults
// https://developer.apple.com/documentation/foundation/userdefaults/1414067-set
UserDefaults().set(dataToSave, forKey: "tagOfData")

// Take our stored data (in previous step) from UserDefaults using the key
// "personData". Optional binding is used to make sure the retrieved data is
// not nil.
// Reference
// https://developer.apple.com/documentation/foundation/userdefaults
// https://developer.apple.com/documentation/foundation/userdefaults/1409590-data
// https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html#//apple_ref/doc/uid/TP40014097-CH5-ID333
if let dataRetrieved = UserDefaults().data(forKey: "tagOfData"),
  // Decode our instance objects from the retrieved data
  // Reference
  // https://developer.apple.com/documentation/foundation/nskeyedunarchiver
  // https://developer.apple.com/documentation/foundation/nskeyedunarchiver/1413894-unarchiveobject
  let anArrayOfPersonsRetrieved = NSKeyedUnarchiver.unarchiveObject(with: dataRetrieved) as? [Person] {
    // See how many bytes the data we retrieved has.
    print(dataRetrieved) // 393 bytes

    // See if the name and age properties are the same as what we stored.
    print(anArrayOfPersonsRetrieved[0].name) // "Cong"
    print(anArrayOfPersonsRetrieved[0].age)  // 45
    print(anArrayOfPersonsRetrieved[1].name) // "Sunny"
    print(anArrayOfPersonsRetrieved[1].age)  // 2
  }

回答by ViTUu

This link can help you

这个链接可以帮助你

It is important your class extend NSObjectand NSCoding, because the convert need be its class, NSCodingis an interface to serialize and deserialize your class

你的类扩展是非常重要的NSObject和NSCoding，因为转换需要是它的类，NSCoding是序列化的界面和反序列化类

Saving custom SWIFT class with NSCoding to UserDefaults

使用 NSCoding 将自定义 SWIFT 类保存到 UserDefaults