如何在没有可选值的情况下将字典数组快速转换为json字符串[重复]

Question

我想将字典数组转换为 json 字符串，所以我使用了

func json(from object: NSMutableArray) -> String? {
    guard let data = try? JSONSerialization.data(withJSONObject: object) else {
        return nil
    }

    return String(data: data, encoding: String.Encoding.utf8)
}

它返回一个json字符串，但在搅拌之前有一个可选

finalString = json(from: saveArray)
print(finalString)

可选("[{\"CreatedOn\":\"2018 年 3 月 29 日星期四\",\"DayName\":\"Wed\",\"EmployeeID\":\"1\",\ "AppointmentType\":\"3\",\"FromTime\":\"09:00:00\",\"AppointmentDate\":\"2018 年 5 月 16 日星期三\",\"ToTime\": \"10:00:00\",\"CreatedBy\":\"40289\",\"PatientID\":\"17586\",\"ResourceID\":\"1\",\"PatientConditionId\ ":\"17590\"},{\"CreatedOn\":\"2018 年 3 月 29 日星期四\",\"DayName\":\"Thu\",\"EmployeeID\":\"1\" ,\"AppointmentType\":\"3\",\"FromTime\":\"09:00:00\",\"AppointmentDate\":\"2018 年 5 月 17 日星期四\",\"ToTime\ ":\"10:00:00\",\"CreatedBy\":\"40289\",\"PatientID\":\"17586\",\"ResourceID\":\"1\",\" PatientConditionId\":\"17590\"},{\"CreatedOn\":\"2018 年 3 月 29 日星期四\",\"DayName\":\"Fri\",\"EmployeeID\":\"1 \",\"AppointmentType\":\"3\",\"FromTime\":\"09:00:00\",\"AppointmentDate\":\"2018 年 5 月 18 日星期五\",\" ToTime\":\"10:00:00\",\"CreatedBy\":\"40289\",\"PatientID\":\"17586\",\"ResourceID\":\"1\", \"PatientConditionId\":\"17590\"}]")

当我打开这个值时......

finalString = json(from: saveArray)
print(finalString!)

然后我得到...

[
{
"CreatedOn": "Thursday, Mar 29, 2018",
"DayName": "Wed",
"EmployeeID": "1",
"AppointmentType": "3",
"FromTime": "09:00:00",
"AppointmentDate": "Wednesday, May 16, 2018",
"ToTime": "10:00:00",
"CreatedBy": "40289",
"PatientID": "17586",
"ResourceID": "1",
"PatientConditionId": "17590"
},
{
"CreatedOn": "Thursday, Mar 29, 2018",
"DayName": "Thu",
"EmployeeID": "1",
"AppointmentType": "3",
"FromTime": "09:00:00",
"AppointmentDate": "Thursday, May 17, 2018",
"ToTime": "10:00:00",
"CreatedBy": "40289",
"PatientID": "17586",
"ResourceID": "1",
"PatientConditionId": "17590"
},
{
"CreatedOn": "Thursday, Mar 29, 2018",
"DayName": "Fri",
"EmployeeID": "1",
"AppointmentType": "3",
"FromTime": "09:00:00",
"AppointmentDate": "Friday, May 18, 2018",
"ToTime": "10:00:00",
"CreatedBy": "40289",
"PatientID": "17586",
"ResourceID": "1",
"PatientConditionId": "17590"
}
]

只是一个数组结构。

现在如何实现没有可选值的json字符串结构?????

Answer 1

可以通过条件绑定来实现

if let finalString = json(from: saveArray) {
  print(finalString) //here final string is unwrapped
} else {
  print("Invalid JSON")
}

或

guard let finalString = json(from: saveArray) else {
   print("finalString is nil")
   return
}

print(finalString)

Answer 2

您将返回值声明为可选

... -> String?

所以即使结果不是，它也总是可选的。

解包或可选绑定可选

finalString! 

if let final = finalString { ...

在打印输出中去掉Optional。

---

更好的解决方案是将函数标记为can throw，并将JSONSerialization的错误交出。与返回可选项相比，这是一种更加一致的错误处理。如果没有错误，则从 Data 对象创建的字符串永远不会是 nil。

不要在 Swift 中使用NSMutableArray。

func json(from object: [[String:Any]]) throws -> String {
    let data = try JSONSerialization.data(withJSONObject: object)
    return String(data: data, encoding: .utf8)!
}

并使用它

do {
   let finalString = json(from: ...
} catch { print(error) }