json - Swift:将结构转换为 JSON？

Question

我创建了一个 struct 并想将其保存为 JSON 文件。

struct Sentence {
    var sentence = ""
    var lang = ""
}

var s = Sentence()
s.sentence = "Hello world"
s.lang = "en"
print(s)

...结果是:

Sentence(sentence: "Hello world", lang: "en")

但是我怎样才能将 struct 对象转换成类似这样的东西:

{
    "sentence": "Hello world",
    "lang": "en"
}

Answer 1

Swift 4 引入了 Codable 协议(protocol)，它提供了一种非常方便的方式来编码和解码自定义结构。

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) }