背景：项目原本是使用HandyJson来做的数据-模型的相互转换，后面测试发现在iOS12.1系统的，HandyJson库会必现崩溃libswiftCoreGraphics image not found，该库作者已经不再更新且不推荐使用了，具体详细原及可以看下我之前的文章：https://www.jianshu.com/p/167167f54a0d
后面就考虑移除HandyJson改为系统Codable去实现数据-模型的相互转换，从Handyjson迁移到Codable的过程中，我发现了如下问题
我发现HandyJson在做转换时，如果json数据的某个字段的类型与model类的对应的字段类型不匹配时，HandyJson会尝试自动帮你进行类型转换，但是在Codable中，类型不匹配会导致错误，换句话说就是必须保证jsonObjct中对应的属性名称是对应的，否则该属性的自动会转换失败，如果想要转换，必须手动实现codable对应的方法。
对于继承类型，无法自动转换该类型的父类或子类属性，如果想要转换，必须手动实现codable对应的方法。
系统对于实体类属性,会根据是可选值或不可选值自动调用对应的方法,如果json这个key为空,但是实体类属性为不可选值,这也会导致对象转换失败。
这几点差异，导致对于每个改动的接口，都需要进行一番调试，查看转换是否正常，耗费了很多时间。
以下为实践过程中总结的一些经验：
// 遵循codable协议,即可自动转化,前提:
// 1.类的父类是NSobject或空
// 2.类的属性类型与json或者jsonObjct中对应的类型是对应的,否则对象会转化失败
// 3.类的属性名称与json或者jsonObjct中对应的属性名称是对应的,否则该属性会转换失败
// 4.如果包含嵌套类型,则嵌套类型也需要实现codable协议
// 5.系统对于实体类属性,会根据是可选值或不可选值自动调用对应的方法,如果json这个key为空,但是实体类属性为不可选值,这也会导致对象转换失败
self.childName = try container.decodeIfPresent(String.self, forKey: .childName)
self.childName = try container.decode(String.self, forKey: .childName)
try cotainer.encodeIfPresent(self.childName, forKey: .childName)
try cotainer.encode(self.childName, forKey: .childName)
// 无法自动转化时
// 1.类如果是子类,需要手动实现enum CodingKeys:/ init(from decoder: Decoder)/ encode(to encoder: Encoder)方法,父类需要遵守codable协议,但可以自动转化
// 2.类的属性类型不对应,需要手动实现enum CodingKeys:/ init(from decoder: Decoder)/ encode(to encoder: Encoder)方法
// 3.类的属性名称不对应,需要手动实现enum CodingKeys,所有属性都必须写出来
public class JsonToModelViewController: UIViewController {
/*
let jsonStr = """
{
"token_expires_timestamp":1680680304281,
"uid":"4478366175",
"token_expires_time":86400,
"isSetPwd":"0",
"token": "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJleHAiOjE2ODA2ODAzMDQyODEsInBheWxvYWQiOiJ7XCJpbWlVaWRcIjpcIjQ0NzgzNjYxNzVcIixcImZsYWdcIjoxfSJ9.KOBDBhs_pnDPdp85UOebQ6lfJy_Tf_w-YhXj0KlTyok",
"refresh_token":"eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJleHAiOjE2ODE4MDM1MDQyODEsInBheWxvYWQiOiJ7XCJpbWlVaWRcIjpcIjQ0NzgzNjYxNzVcIixcImZsYWdcIjoyfSJ9.0AJs5VFJjIOfOG3VjoJ9zx75taRS2xFGbrpEamyWoAk",
"refresh_token_expires_timestamp":1681803504281,
"authCode":"0167247243702923",
"refresh_token_expires_time":1209600,
"currentUtcDate":1680593904281,
}
"""
*/
let jsonStr = """
{
"name": "张三",
"age": 20,
"description": "A handsome boy.",
"childName": "小a"
}
"""
let jsonLabel = UILabel(frame: CGRectZero)
let jsonToModelButton = UIButton(type: .system)
let modelToJsonButton = UIButton(type: .system)
let modelToJsonObjButton = UIButton(type: .system)
public override func viewDidLoad() {
super.viewDidLoad()
initViews()
}
func initViews() {
self.navigationItem.title = "json转模型"
self.view.backgroundColor = .white
jsonLabel.text = jsonStr
jsonLabel.numberOfLines = 0
jsonLabel.adjustsFontSizeToFitWidth = true
self.view.addSubview(jsonLabel)
jsonToModelButton.setTitle("json转model", for: .normal)
jsonToModelButton.backgroundColor = .gray
jsonToModelButton.addTarget(self, action: #selector(jsonToModel), for: .touchUpInside)
self.view.addSubview(jsonToModelButton)
modelToJsonButton.setTitle("model转json", for: .normal)
modelToJsonButton.backgroundColor = .gray
modelToJsonButton.addTarget(self, action: #selector(modelToJson), for: .touchUpInside)
self.view.addSubview(modelToJsonButton)
modelToJsonObjButton.setTitle("model转jsonObj", for: .normal)
modelToJsonObjButton.backgroundColor = .gray
modelToJsonObjButton.addTarget(self, action: #selector(modelToJsonObj), for: .touchUpInside)
self.view.addSubview(modelToJsonObjButton)
}
public override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
jsonLabel.snp.makeConstraints { make in
make.left.equalToSuperview().offset(10)
make.right.equalToSuperview().offset(-10)
make.top.equalToSuperview().offset(64)
make.height.lessThanOrEqualTo(300)
}
jsonToModelButton.snp.makeConstraints { make in
make.left.equalToSuperview().offset(10)
make.right.equalToSuperview().offset(-10)
make.top.equalTo(jsonLabel.snp.bottom).offset(10)
make.height.equalTo(44)
}
modelToJsonButton.snp.makeConstraints { make in
make.left.equalToSuperview().offset(10)
make.right.equalToSuperview().offset(-10)
make.top.equalTo(jsonToModelButton.snp.bottom).offset(10)
make.height.equalTo(44)
}
modelToJsonObjButton.snp.makeConstraints { make in
make.left.equalToSuperview().offset(10)
make.right.equalToSuperview().offset(-10)
make.top.equalTo(modelToJsonButton.snp.bottom).offset(10)
make.height.equalTo(44)
}
}
@objc private func jsonToModel() {
do {
// let model = try JSONDecoder().decode(ILAuthInfo.self, from: jsonStr.data(using: .utf8)!)
// let model = try JSONDecoder().decode(ILTestModel.self, from: jsonStr.data(using: .utf8)!)
let model = try JSONDecoder().decode(ILTestChildModel.self, from: jsonStr.data(using: .utf8)!)
print("转换得到的模型:\(model)")
}catch {
imiLogE("转换失败:\(error)")
}
let jsonStr = """
{"total":2,"cameraCount":1,"items":[{"name":"cm1"},{"name":"cm2"}]}
"""
do {
let model = try JSONDecoder().decode(ILHomeRoomModel.self, from: jsonStr.data(using: .utf8)!)
print("转换得到的模型:\(model)")
}catch {
imiLogE("转换失败:\(error)")
}
}
@objc private func modelToJson() {
let m1 = ILTestModel()
m1.name = "张三"
let m2 = ILTestModel()
m2.name = "李四"
do {
let jsonData = try JSONEncoder().encode([m1, m2])
let json = String(data: jsonData, encoding: .utf8)
print("转换得到的json1:\(json ?? "空")")
}catch{
imiLogE("转换失败:\(error)")
}
let m = ILHomeRoomModel()
m.total = 2
m.cameraCount = 1
let cm1 = ILRoomItem()
cm1.name = "cm1"
let cm2 = ILRoomItem()
cm2.name = "cm2"
m.items = [cm1, cm2]
do {
let jsonData = try JSONEncoder().encode(m)
let json = String(data: jsonData, encoding: .utf8)
print("转换得到的json2:\(json ?? "空")")
}catch{
imiLogE("转换失败:\(error)")
}
let bm = ILTestBigModel()
bm.bigName = "大名"
bm.child = m2
do {
let jsonData = try JSONEncoder().encode(bm)
let json = String(data: jsonData, encoding: .utf8)
print("转换得到的json3:\(json ?? "空")")
}catch{
imiLogE("转换失败:\(error)")
}
}
@objc private func modelToJsonObj() {
let model = ILTestModel()
model.name = "李四"
model.smallName = "a"
model.des = "啊哈"
model.age = 22
let jsonObj = ILCodableUtil.modelToJsonObject(model) as? [String: Any]
}
}
@objcMembers
public class ILTestModel: NSObject, Codable {
var name: String?
var smallName: String?
var des: String?
var age: Int = 0
public override var description: String {
"name:\(name ?? "空"), smallName:\(smallName ?? "空"), des:\(des ?? "空"), age:\(age)"
}
// enum CodingKeys: String, CodingKey {
// case name
// case smallName
// case des = "description"
// case age
// }
//手动实现
/*
public required init(from decoder: Decoder) throws {
super.init()
let container = try decoder.container(keyedBy: CodingKeys.self)
self.nickName = try container.decodeIfPresent(String.self, forKey: .nickName)
self.deviceName = try container.decodeIfPresent(String.self, forKey: .deviceName)
self.mac = try container.decodeIfPresent(String.self, forKey: .mac)
self.productKey = try container.decodeIfPresent(String.self, forKey: .productKey)
self.token = try container.decodeIfPresent(String.self, forKey: .token)
self.categoryKey = try container.decodeIfPresent(String.self, forKey: .categoryKey)
//特殊处理一下字典
let dicData = try container.decodeIfPresent(Data.self, forKey: .extraDeviceInfo)
self.extraDeviceInfo = ILLocalDeviceKeychainUtil.dataToDictionary(dicData);
}
public func encode(to encoder: Encoder) throws {
//super.encode(to: encoder)
var cotainer = encoder.container(keyedBy: CodingKeys.self)
try cotainer.encodeIfPresent(self.nickName, forKey: .nickName)
try cotainer.encodeIfPresent(self.deviceName, forKey: .deviceName)
try cotainer.encodeIfPresent(self.mac, forKey: .mac)
try cotainer.encodeIfPresent(self.productKey, forKey: .productKey)
try cotainer.encodeIfPresent(self.token, forKey: .token)
try cotainer.encodeIfPresent(self.categoryKey, forKey: .categoryKey)
//特殊处理一下字典
if let dicData = ILLocalDeviceKeychainUtil.dictionaryToData(self.extraDeviceInfo) {
try cotainer.encodeIfPresent(dicData, forKey: .extraDeviceInfo)
}
}
*/
}
@objcMembers public class ILTestBigModel: NSObject, Codable {
var bigName: String?
var child: ILTestModel?
}
/// 子类想要使用Codable转换,必须手写以下实现
/// 与现有的 NSCoding API (NSKeyedArchiver) 不同，为了灵活性和安全性，新的 Swift 4 Codable 实现不会将有关编码类型的类型信息写入生成的档案中。因此，在解码时，API 只能使用您提供的具体类型来解码值（在您的情况下是超类类型）。
@objcMembers public class ILTestChildModel: ILTestModel {
var childName: String?
enum CodingKeys: String, CodingKey {
case childName = "childName"
}
public required init(from decoder: Decoder) throws {
try super.init(from: decoder)
let container = try decoder.container(keyedBy: CodingKeys.self)
self.childName = try container.decodeIfPresent(String.self, forKey: .childName)
}
public override func encode(to encoder: Encoder) throws {
var cotainer = encoder.container(keyedBy: CodingKeys.self)
try cotainer.encodeIfPresent(self.childName, forKey: .childName)
}
}
