如何从Decodable获取utf8解码字符串? [英] How to get utf8 decoded string from Decodable?

问题描述

问题是我有一个json数据包含和编码的字符串，例如:

The issue is that I have a json data contains and encoded string, example:

let jsonData = "{ \"encoded\": \"SGVsbG8gV29ybGQh\" }".data(using: .utf8)

我需要获取"SGVsbG8gV29ybGQh"字符串的解码值.

What I need is to get the decoded value of "SGVsbG8gV29ybGQh" string.

实际上，我可以通过执行以下操作来获得所需的输出:

Actually I could get the desired output by implementing:

let decoder = JSONDecoder()
let result = try! decoder.decode(Result.self, from: jsonData!)

if let data = Data(base64Encoded: result.encoded), let decodedString = String(data: data, encoding: .utf8) {
    print(decodedString) // Hello World!
}

我要做的是:

• 将我从json(result.encoded)获得的编码字符串转换为数据对象

• convert the encoded string That I got from the json (result.encoded) to Data object

再次将数据对象转换为字符串.

Reconvert the data object to a string again.

但是，这似乎不仅仅是一个步骤，在这种情况下是否有更好的方法可循?

However, it seems to be more than just a one step to achieve it, is there better approach(es) to be followed for such a case?

推荐答案

在处理Decodable的编码字符串时，实际上您甚至不必将属性声明为String，只需直接声明它即可为Data.

When it comes to handle encoded string for a Decodable, actually you don't even have to declare the property as String, just directly declare it as Data.

因此，对于您的情况，您应该将encoded编辑为:

So for your case, what you should do is to edit encoded to as:

struct Result: Decodable {
    var encoded: Data
}

因此:

let decoder = JSONDecoder()
let result = try! decoder.decode(Result.self, from: jsonData!)

let decodedString = String(data: result.encoded, encoding: String.Encoding.utf8)
print(decodedString ?? "") // decodedString

---

请记住，这与处理可解码项的日期非常相似，例如，请考虑以下json数据:

---

Keep in mind that it is a pretty similar case to handling Dates for decodables, as an example consider that we have the following json data:

let jsonData = "{ \"timestamp\": 1527765459 }".data(using: .utf8)

很显然，您不会收到timestamp作为数字并将其转换为Date对象，而是将其声明为Date:

Obviously, you won't receive timestamp as number and convert it to a Date object, instead you would declare it as Date:

struct Result: Decodable {
    var timestamp: Date
}

因此:

let decoder = JSONDecoder()
// usually, you should edit decoding strategy for the date to get the expected result:
decoder.dateDecodingStrategy = .secondsSince1970

let result = try! decoder.decode(Result.self, from: jsonData!)
print(result.timestamp) // 2018-05-31 11:17:39 +0000

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