How to check response codable value is empty or not?

问题

I am new to swift and codable too. I have below codable. I am getting all response of API in "RecentResult". I want to check "data" is empty or not. How do I check it?

struct RecentResult: Codable 
    {
        let input: Input
        let commandResult: CommandResultClass
    }

    struct CommandResultClass: Codable {
        let success: Int
        let message: String
        let data: DataClass
    }

    struct DataClass: Codable {
        let recentCount: String

        enum CodingKeys: String, CodingKey {
            case recentCount = "RecentCount"
         }
    }

To decode I am using this line but I am not getting how do I check for "data" is empty of not.

let strResponseData = try JSONDecoder().decode(RecentResult.self, from: data!)

回答1:

General tip for when you have something like an optional in your data...

If you have this ..

struct example: Decodable {
  let name: String
  let nickname: String
  let tag: String
}

those three HAVE TO be there, they can't be "nil", they cannot be nonexistent in the JSON.

So if "nickname" is simply not in the json, it just won't parse.

On the other hand. If you do this, notice the question mark:

struct example: Decodable {
  let name: String
  let nickname: String?
  let tag: String
}

then the .nickname field can actually be nil

So then, you can say something like

if blah.nickname == nil { print("no nickname in the json!") }

You could say the literal answer to your question "How to check if field XYZ is empty" is "if strResponseData.xyz == nil" ...

But you have to indicate to the parser that in the json it may be either nil (ie, the json looks like this ... "nickname":nil ) or it is just plain missing from the json (there's just no field "nickname" in the json).

The way you do that is with the "?".

来源：https://stackoverflow.com/questions/60905397/how-to-check-response-codable-value-is-empty-or-not

标签

ios

swift

swift5.1