Swift中的json操作

在app开发中，app一般都会和后端进行交互，后端接口返回的是json格式的字符串，对json的操作是必须掌握的技能。

在Swfit中对json操作最常用的是两种方式，使用JSONSerialization或者使用JSONDecoder和JSONEncoder。下面详细介绍这两种方式的使用方法。

1、JSONSerialization

使用JSONSerialization可以方便的对json数据进行编码或者解码。

1.1、使用JSONSerialization对json数据进行解码

swift提供 两个方法对json数据进行解码

/// Returns a Foundation object from given JSON data.
/// 把JSON数据转换成对象，返回Any类型
class func jsonObject(with: Data, options: JSONSerialization.ReadingOptions) -> Any

/// Returns a Foundation object from JSON data in a given stream.
/// 把InputStream流中的数据转换成对象，返回Any类型
class func jsonObject(with: InputStream, options: JSONSerialization.ReadingOptions) -> Any

1.2、使用JSONSerialization对符合格式要求的数据进行JSON编码

swift也提供了两个方法对用于JSON编码

/// Returns JSON data from a Foundation object.
/// 把对象转换成Data类型的数据
class func data(withJSONObject: Any, options: JSONSerialization.WritingOptions) -> Data

/// Writes a given JSON object to a stream.
/// 把JSON对象写入stream流
class func writeJSONObject(Any, to: OutputStream, options: JSONSerialization.WritingOptions, error: NSErrorPointer) -> Int

2、JSONDecoder&&JSONEncoder

2.1、JSONDecoder解码

struct GroceryProduct: Codable {
    var name: String
    var points: Int
    var description: String?
}

let json = """
{
    "name": "Durian",
    "points": 600,
    "description": "A fruit with a distinctive scent."
}
""".data(using: .utf8)!

let decoder = JSONDecoder()
let product = try decoder.decode(GroceryProduct.self, from: json)

print(product.name) // Prints "Durian"

2.2、JSONEncoder

struct GroceryProduct: Codable {
    var name: String
    var points: Int
    var description: String?
}

let pear = GroceryProduct(name: "Pear", points: 250, description: "A ripe pear.")

let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted

let data = try encoder.encode(pear)
print(String(data: data, encoding: .utf8)!)

/* Prints:
 {
   "name" : "Pear",
   "points" : 250,
   "description" : "A ripe pear."
 }
*/