Swift 4 JSONEncoder不能对String或Int进行编码，但它们遵循Codable协议

Question

let encoder = JSONEncoder()

do {
   let encodData = try encoder.encode("test string") // same as Int type
   print(encodData) // nil
} catch let err {
   print(err.localizedDescription) // The data couldn’t be written because it isn’t in the correct format.
}

如何编码这些类型值

Answer 1

顶级（根）JSON对象只能是数组或字典。例如：

do {
    let encoder = JSONEncoder()
    let encodData = try encoder.encode(["test string"])
    print(String(data: encodData, encoding: .utf8)!) 
    // ["test string"]

} catch {
    print(error.localizedDescription)
}