JSONSerialization：是什么、Foundation类方法及工作原理

import Foundation

// 使用JSONSerialization的基本结构
let jsonString = """
{
    "id": 1,
    "name": "John Doe",
    "email": "john@example.com"
}
"""

guard let jsonData = jsonString.data(using: .utf8) else {
    return
}

do {
    let json = try JSONSerialization
        .jsonObject(with: jsonData,
                       options: .mutableContainers)
    print(json)
} catch {
    print("JSON解析错误：\(error)")
}

let jsonString = """
{
    "products": [
        {"id": 1, "name": "iPhone", "price": 999},
        {"id": 2, "name": "iPad", "price": 799}
    ]
}
"""
let data = Data(jsonString.utf8)

if let json = try? JSONSerialization
    .jsonObject(with: data) as? [String: Any],
    let products = json["products"] as? [[String: Any]] {

    for product in products {
        if let name = product["name"] as? String {
            print("产品：\(name)")
        }
    }
}

// 反向序列化：对象 -> JSON
let outputDict: [String: Any] = ["status": "ok", "count": 42]
if let outputData = try? JSONSerialization
    .data(withJSONObject: outputDict,
                options: .prettyPrinted) {
    String(data: outputData, encoding: .utf8)
}

// 解析API响应
func parseUserResponse(data: Data) {
    do {
        guard let json = try JSONSerialization
            .jsonObject(with: data) as? [String: Any]
        else { return }

        guard let userId = json["id"] as? Int,
              let name = json["name"] as? String
        else {
            throw ParsingError.missingField
        }

        print("用户：\(name) (ID：\(userId))")

    } catch let error as ParsingError {
        print("解析失败：\(error)")
    } catch {
        print("意外错误：\(error)")
    }
}

enum ParsingError: Error {
    case missingField
    case invalidType
}

// 处理不同类型的错误
func safeParse(jsonData: Data) {
    do {
        let object = try JSONSerialization
            .jsonObject(with: jsonData,
                           options: .fragmentsAllowed)

        if let dictionary = object as? [String: Any] {
            print("包含\(dictionary.count)个键的字典")
        } else if let array = object as? [Any] {
            print("包含\(array.count)个项目的数组")
        }

    } catch CocoaError.propertyListReadCorrupt {
        print("损坏的JSON数据")
    } catch let error as CocoaError {
        print("Cocoa错误：\(error)")
    } catch {
        print("未知错误：\(error)")
    }
}

// 序列化前检查对象有效性
let testObject: [String: Any] = ["key": "value", "nested": ["a": 1]]
if JSONSerialization.isValidJSONObject(testObject) {
    print("有效的JSON对象")
}