json解析笔记

Json解析这里主要是想说明一下options的作用

1.对象转成jsonString : 进行转化前为了安全最好先判断isValidJSONObject, 原因如下：

/// Generate JSON data from a Foundation object
let jsonObj1 = "这是数据" // 1.解析非集合对象options须有.fragmentsAllowed，否则奔溃
let jsonObj2 = [6] // 数组类型options不需要.fragmentsAllowed也能解析
let jsonObj3 = ["key":"value"] // 这种是正常的字典
let jsonObj4 = ["msg" : "haha!", 
                "data":["key":"value"],
            "fdasfds" :[12]] as [String : Any] // 不需要.fragmentsAllowed能解析
let jsonObj5 : Set = ["value1", "value2"] // 集合类型加什么options都会奔溃

let bool1 = JSONSerialization.isValidJSONObject(jsonObj1) // false
let bool2 = JSONSerialization.isValidJSONObject(jsonObj2) // true
let bool3 = JSONSerialization.isValidJSONObject(jsonObj3)// true
let bool4 = JSONSerialization.isValidJSONObject(jsonObj4)// true
let bool5 = JSONSerialization.isValidJSONObject(jsonObj5)// false

let data = try? JSONSerialization.data(withJSONObject: jsonObj, 
options: [.prettyPrinted, // 1.打印美化，转成字符串会自动加换行符和缩进
.sortedKeys, // 2.排序key
.fragmentsAllowed, // 3.允许非字典、非数组类型解析
.withoutEscapingSlashes])// 4.内容里面包含斜杆"\"时不用添加斜杆转义 

结论：

func getJSONStringFromDictionary(_ dictionary: Dictionary<AnyHashable, Any>) -> String {
    guard dictionary.count > 0, JSONSerialization.isValidJSONObject(dictionary) else {
        print("非有效json")
        return ""
    }
// options:参数根据上述的介绍自己选择
    let data = try! JSONSerialization.data(withJSONObject: dictionary, options: [])
    let JSONString = NSString(data: data, encoding: String.Encoding.utf8.rawValue)
    return JSONString! as String
}

2. jsonString转成字典或者数组

let jsonString1 = "\"aaaa\"" // 要解析非键值对，需要option有.allowFragments
let jsonString2 = "[{\"key1\":\"value1\", \"key2\" : \"value2\"}, {\"key3\":\"value3\", \"key3\" : \"value3\"}]"// 能解析
let jsonString3 = "{\"key1\":\"value1\", \"key2\" : \"value2\"}"// 能解析
let jsonString4 = "{\"data\": [{\"key1\":\"value1\"}, {\"key2\" : \"value2\"}]}"// 能解析
let jsonString5 = "aaaaaa"// 非键值对或者非""里面的字符串，解析都是空的
let jsonString = jsonString1
let jsonObj = getJsonObj(with: jsonString)

func getJsonObj(with jsonString: String) -> Any! {
    guard jsonString.count > 0 else {
        return nil
    }
    let data = jsonString.data(using: String.Encoding.utf8)!
    do {// 在jsonString1时，第一个有.allowFragments能解析，第二个会抛出异常
        let _ = try JSONSerialization.jsonObject(with: data, options: .allowFragments)
        let _ = try JSONSerialization.jsonObject(with: data, options: [])
    } catch let error as NSError {
        print(error)
    }
    let jsonObj2 = try? JSONSerialization.jsonObject(with: data, options: [.mutableContainers, // 解析出来数组和字典是可变的
.mutableLeaves, // 解析出来的字符串是可变的
.allowFragments])// 允许不是键值对的单独值
    let jsonObj = try? JSONSerialization.jsonObject(with: data, options: [])
    return jsonObj
}

结论：

func getJsonObj(with jsonString: String) -> Any! {
    guard jsonString.count > 0 else {
        return nil
    }
    let data = jsonString.data(using: String.Encoding.utf8)!
    let jsonObj = try? JSONSerialization.jsonObject(with: data, options: [])
    return jsonObj
}