崩溃：在 Swift 3 中将字典转换为 Json 字符串
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Crash : Convert dictionary to Json string in Swift 3
提问by W.venus
I'm trying to convert my swift dictionary to Json string but getting strange crash by saying
我正在尝试将我的 swift 字典转换为 Json 字符串，但说奇怪的崩溃
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Invalid type in JSON write (_SwiftValue)'
由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“JSON 写入中的类型无效（_SwiftValue）”
My code:
我的代码：
let jsonObject: [String: AnyObject] = [
"firstname": "aaa",
"lastname": "sss",
"email": "my_email",
"nickname": "ddd",
"password": "123",
"username": "qqq"
]
do {
let jsonData = try JSONSerialization.data(withJSONObject: jsonObject, options: .prettyPrinted)
// here "jsonData" is the dictionary encoded in JSON data
let decoded = try JSONSerialization.jsonObject(with: jsonData, options: [])
// here "decoded" is of type `Any`, decoded from JSON data
// you can now cast it with the right type
if let dictFromJSON = decoded as? [String:String] {
// use dictFromJSON
}
} catch {
print(error.localizedDescription)
}
Please help me!
请帮我！
Regards.
问候。
回答by Josh Homann
Stringis not of type AnyObject. Objects are reference types, but Stringin swift has value semantics. A Stringhowever, can be of type Any, so the code below works. I suggest you read up on reference types and value semantic types in Swift; its a subtle but important distinction and its also different from what you expect from most other languages, where String is often a reference type (including objective C).
String不是AnyObject类型。对象是引用类型，但swift 中的String具有值语义。然而，一个String可以是Any类型，所以下面的代码有效。我建议你阅读 Swift 中的引用类型和值语义类型；这是一个微妙但重要的区别，它也不同于您对大多数其他语言的期望，其中 String 通常是一种引用类型（包括目标 C）。
let jsonObject: [String: Any] = [
"firstname": "aaa",
"lastname": "sss",
"email": "my_email",
"nickname": "ddd",
"password": "123",
"username": "qqq"
]
do {
let jsonData = try JSONSerialization.data(withJSONObject: jsonObject, options: .prettyPrinted)
// here "jsonData" is the dictionary encoded in JSON data
let decoded = try JSONSerialization.jsonObject(with: jsonData, options: [])
// here "decoded" is of type `Any`, decoded from JSON data
// you can now cast it with the right type
if let dictFromJSON = decoded as? [String:String] {
print(dictFromJSON)
}
} catch {
print(error.localizedDescription)
}
