Swift:将结构转换为JSON?
我创建了一个Swift:将结构转换为JSON?,json,swift,struct,nsjsonserialization,Json,Swift,Struct,Nsjsonserialization,我创建了一个struct,并希望将其保存为JSON文件 struct Sentence { var sentence = "" var lang = "" } var s = Sentence() s.sentence = "Hello world" s.lang = "en" print(s) …这导致: Sentence(sentence: "Hello world", lang: "en") 但是如何将struct对象转换为如下内容: { "sentence"
struct
,并希望将其保存为JSON文件
struct Sentence {
var sentence = ""
var lang = ""
}
var s = Sentence()
s.sentence = "Hello world"
s.lang = "en"
print(s)
…这导致:
Sentence(sentence: "Hello world", lang: "en")
但是如何将struct
对象转换为如下内容:
{
"sentence": "Hello world",
"lang": "en"
}
使用
使用此函数,您可能需要创建一个返回JSON序列化字符串的函数。在这个函数中,您可以获取所需的属性并从中创建NSDictionary,然后使用上面提到的类
大概是这样的:
struct Sentence {
var sentence = ""
var lang = ""
func toJSON() -> String? {
let props = ["Sentence": self.sentence, "lang": lang]
do {
let jsonData = try NSJSONSerialization.dataWithJSONObject(props,
options: .PrettyPrinted)
return String(data: jsonData, encoding: NSUTF8StringEncoding)
} catch let error {
print("error converting to json: \(error)")
return nil
}
}
}
因为您的结构只有两个属性,所以自己构建JSON字符串可能更容易。Swift 4引入了
Codable
协议,它提供了一种非常方便的编码和解码自定义结构的方法
struct Sentence : Codable {
let sentence : String
let lang : String
}
let sentences = [Sentence(sentence: "Hello world", lang: "en"),
Sentence(sentence: "Hallo Welt", lang: "de")]
do {
let jsonData = try JSONEncoder().encode(sentences)
let jsonString = String(data: jsonData, encoding: .utf8)!
print(jsonString) // [{"sentence":"Hello world","lang":"en"},{"sentence":"Hallo Welt","lang":"de"}]
// and decode it back
let decodedSentences = try JSONDecoder().decode([Sentence].self, from: jsonData)
print(decodedSentences)
} catch { print(error) }
Swift 4支持可编码协议,例如
struct Sentence: Encodable {
var sentence: String?
var lang: String?
}
let sentence = Sentence(sentence: "Hello world", lang: "en")
现在,您可以使用JSONEncoder自动将结构转换为JSON:
let jsonEncoder = JSONEncoder()
let jsonData = try jsonEncoder.encode(sentence)
打印出来:
let jsonString = String(data: jsonData, encoding: .utf8)
print(jsonString)
{
"sentence": "Hello world",
"lang": "en"
}
这是一个不错的扩展和JSON编码/解码方法:
extension Encodable {
func toJSONString() -> String {
let jsonData = try! JSONEncoder().encode(self)
return String(data: jsonData, encoding: .utf8)!
}
}
func instantiate<T: Decodable>(jsonString: String) -> T? {
return try? JSONDecoder().decode(T.self, from: jsonString.data(using: .utf8)!)
}
可能的重复(作为提示,您只能将数组或字典转换为JSON,因此基本上您需要以JSON格式输入值的字典表示形式)。基本上,如果我可以将结构转换为类似JSON的字符串,那就太好了。当只有数组和字典可转换为JSON时,我的问题是:如何将结构转换为字典?有第三方库,如。但是,我没有这方面的经验。
toJSON()
的返回应该是NSData
。另外,您创建的props
字典中的第二个键是错误的。我已将第二个键更新为字符串,谢谢。第二点取决于用户想要返回什么我们如何将其重新转换为struct?@BhavinRamani添加一个初始值设定项init(dict:[String:Any]){…`并提取values@BhavinRamani,您可以自动完成,下面是一个很棒的教程:
struct Sentence: Codable {
var sentence = ""
var lang = ""
}
let sentence = Sentence(sentence: "Hello world", lang: "en")
let jsonStr = sentence.toJSONString()
print(jsonStr) // prints {"lang":"en","sentence":"Hello world"}
let sentenceFromJSON: Sentence? = instantiate(jsonString: jsonStr)
print(sentenceFromJSON!) // same as original sentence