Swift Json解析与model互转

//为了将 JSON 字符串转化为 Beer 类型的实例，我们需要将 Beer 类型标记为 Codable。enum BeerStyle: String, Codable {
case ipa
case stout
case kolsch
}struct Beer: Codable {
let name: String
let abv: Float
let brewery: String
let style: BeerStyle
}/// json 的key与结构体属性不是对应的，需要自定义键值名
struct Beer2: Codable {
let name: String
let abv: Float
let brewery: String
let style: BeerStyle private enum CodingKeys: String, CodingKey {
case name
case abv = "alcohol_by_volume"
case brewery = "brewery_name"
case style
} init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
name = try values.decode(String.self, forKey: Beer2.CodingKeys.name)
abv = try values.decode(Float.self, forKey: Beer2.CodingKeys.abv)
brewery = try values.decode(String.self, forKey: Beer2.CodingKeys.brewery)
style = try values.decode(BeerStyle.self, forKey: Beer2.CodingKeys.style)
}
}class Wine: NSObject, Codable {
var abv: Float?
}class Beer3: Wine {
var name: String?
var brewery: String?
var style: BeerStyle?
}class Beer4: Wine {
var name: String?
var brewery: String?
var style: BeerStyle? private enum CodingKeys: String, CodingKey {
case name
case abv = "alcohol_by_volume"
case brewery = "brewery_name"
case style
} /// 自定义编码
override func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self) try container.encode(name, forKey: .name)
try container.encode(abv, forKey: .abv)
try container.encode(brewery, forKey: .brewery)
try container.encode(style, forKey: .style)
} /// 自定义解码
required init(from decoder: Decoder) throws {
super.init()
let values = try decoder.container(keyedBy: CodingKeys.self)
name = try values.decode(String.self, forKey: Beer4.CodingKeys.name)
abv = try values.decode(Float.self, forKey: Beer4.CodingKeys.abv)
brewery = try values.decode(String.self, forKey: Beer4.CodingKeys.brewery)
style = try values.decode(BeerStyle.self, forKey: Beer4.CodingKeys.style)
}
}/// 时间格式处理
struct Foo: Encodable {
let date: Date
}/// 浮点类型处理
struct Numbers: Decodable {
let a: Float
let b: Float
let c: Float
}

import UIKitclass jsonViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad() jsonFunc1()
jsonFunc2()
jsonFunc3()
jsonFunc4()
jsonFunc7()
jsonFunc8()
}
}// MARK: https://segmentfault.com/a/1190000009929819#articleHeader9extension jsonViewController {
/// JSON 数据结构和Model 对象结构一致
func jsonFunc1() {
let jsonString: String = "{\"name\":\"Endeavor\",\"abv\":8.9,\"brewery\":\"Saint Arnold\",\"style\":\"ipa\"}"
let jsonData = jsonString.data(using: String.Encoding.utf8)
let decoder = JSONDecoder()
// JSON 数据解析为 Beer 实例对象
let beer = try! decoder.decode(Beer.self, from: jsonData!) print("name=\(beer.name),abv=\(beer.abv),brewery=\(beer.brewery),style=\(beer.style)")
/* 打印
name=Endeavor,abv=8.9,brewery=Saint Arnold,style=ipa
*/ let encoder = JSONEncoder()
// 默认 outputFormatting 属性值为 .compact，输出效果如上。如果将其改为 .prettyPrinted 后就能获得更好的阅读体检
encoder.outputFormatting = .prettyPrinted
// 将 Beer 实例转化为 JSON
let jsonData2 = try! encoder.encode(beer) print(String(bytes: jsonData2, encoding: String.Encoding.utf8) ?? "") /* 打印
{
"style" : "ipa",
"brewery" : "Saint Arnold",
"name" : "Endeavor",
"abv" : 8.8999996185302734
}
*/
} /// JSON 数据结构和Model 对象结构不一致,自定义键值名
func jsonFunc2() {
let jsonString: String = "{\"name\":\"Endeavor\",\"alcohol_by_volume\":8.9,\"brewery_name\":\"Saint Arnold\",\"style\":\"ipa\"}"
let jsonData = jsonString.data(using: String.Encoding.utf8)
let decoder = JSONDecoder()
// JSON 数据解析为 Beer 实例对象
let beer = try! decoder.decode(Beer2.self, from: jsonData!) print("name=\(beer.name),abv=\(beer.abv),brewery=\(beer.brewery),style=\(beer.style)")
/* 打印
name=Endeavor,abv=8.9,brewery=Saint Arnold,style=ipa
*/ let encoder = JSONEncoder()
// 默认 outputFormatting 属性值为 .compact，输出效果如上。如果将其改为 .prettyPrinted 后就能获得更好的阅读体检
encoder.outputFormatting = .prettyPrinted
// 将 Beer 实例转化为 JSON
let jsonData2 = try! encoder.encode(beer) print(String(bytes: jsonData2, encoding: String.Encoding.utf8) ?? "")
/* 打印
{
"style" : "ipa",
"name" : "Endeavor",
"brewery_name" : "Saint Arnold",
"alcohol_by_volume" : 8.8999996185302734
}
*/
} /// Codable 默认实现无法覆盖继承这种情况
func jsonFunc3() {
let jsonDic: [String: Any] = ["name": "Endeavor", "abv": 8.9, "brewery": "Saint Arnold", "style": "ipa"]
let jsonData = JSONToData(obj: jsonDic) let decoder = JSONDecoder()
// JSON 数据解析为 Beer 实例对象
let beer = try! decoder.decode(Beer3.self, from: jsonData) print("name=\(String(describing: beer.name)),abv=\(String(describing: beer.abv)),brewery=\(String(describing: beer.brewery)),style=\(String(describing: beer.style))")
/* 打印
name=nil,abv=Optional(8.9),brewery=nil,style=nil
*/ //解析成功但是 name、brewery、style 三个属性全部为 nil,显然，这不是我们想要的结果。Codable 默认实现无法覆盖继承这种情况
} /// 解决 无法覆盖继承的问题，自定义解码和编码
func jsonFunc4() {
let jsonString: String = "{\"name\":\"Endeavor\",\"alcohol_by_volume\":8.9,\"brewery_name\":\"Saint Arnold\",\"style\":\"ipa\"}"
let jsonData = jsonString.data(using: String.Encoding.utf8)
let decoder = JSONDecoder()
// JSON 数据解析为 Beer 实例对象
let beer = try! decoder.decode(Beer4.self, from: jsonData!) print("name=\(String(describing: beer.name)),abv=\(String(describing: beer.abv)),brewery=\(String(describing: beer.brewery)),style=\(String(describing: beer.style))")
/* 打印
name=Optional("Endeavor"),abv=Optional(8.9),brewery=Optional("Saint Arnold"),style=Optional(abcProject.BeerStyle.ipa)
*/ let encoder = JSONEncoder()
// 默认 outputFormatting 属性值为 .compact，输出效果如上。如果将其改为 .prettyPrinted 后就能获得更好的阅读体检
encoder.outputFormatting = .prettyPrinted
// 将 Beer 实例转化为 JSON
let jsonData2 = try! encoder.encode(beer) print(String(bytes: jsonData2, encoding: String.Encoding.utf8) ?? "")
/* 打印
{
"style" : "ipa",
"name" : "Endeavor",
"brewery_name" : "Saint Arnold",
"alcohol_by_volume" : 8.8999996185302734
}
*/
} /// 时间格式处理
func jsonFunc7() {
let encoder = JSONEncoder()
encoder.dateEncodingStrategy = .iso8601
let foo = Foo(date: Date())
let jsonData2 = try! encoder.encode(foo) print(String(bytes: jsonData2, encoding: String.Encoding.utf8) ?? "") /*
其他日期编码格式选择如下： .formatted(DateFormatter) - 当你的日期字符串是非标准格式时使用。需要提供你自己的日期格式化器实例。
.custom( (Date, Encoder) throws -> Void ) - 当你需要真正意义上的自定义时，使用一个闭包进行实现。
.millisecondsSince1970、 .secondsSince1970 - 这在 API 设计中不是很常见。 由于时区信息完全不在编码表示中，所以不建议使用这样的格式，这使得人们更容易做出错误的假设。
对日期进行 Decoding 时基本上是相同的选项，但是 .custom 形式是 .custom( (Decoder) throws -> Date )，所以我们给了一个解码器并将任意类型转换为日期格式。 */
} /// 浮点类型处理
func jsonFunc8() {
let jsonString: String = "{\"a\": \"NaN\", \"b\": \"+Infinity\", \"c\": \"-Infinity\" }"
let jsonData = jsonString.data(using: String.Encoding.utf8)
let decoder = JSONDecoder() decoder.nonConformingFloatDecodingStrategy =
.convertFromString(
positiveInfinity: "+Infinity",
negativeInfinity: "-Infinity",
nan: "NaN") let numbers = try! decoder.decode(Numbers.self, from: jsonData!)
dump(numbers) /* 打印 ▿ abcProject.Numbers
- a: nan
- b: inf
- c: -inf */
}
}