In a method, how to access a structure's property with String parameter in dot syntax way

Question

Sorry, maybe the title seemed hard to understand.

Here is the situation:

A structure with google API URL properties, which are wrapped together and will be stored as Data in userDefaults.

Code Block struct googleApiLibrary: Codable {
    let authUrl: URL
    let tokenUrl: URL
    let userinfoUrl: URL
}

A function with a parameter, Its job is to retrieve the googleApiLibrary from UserDefault, decode back to structure and get the corresponding URL based on the parameter key provided.

Code Block func loadGmailApiUrl(forKey key: String) -> URL {
    guard let encodedValue = defaults.object(forKey: "gmailApiLibrary") as? Data,
       let decodedValue = try? JSONDecoder().decode(GmailApiLibrary.self, from: encodedValue) else { return }
    return decodedValue.<???>
  }

The problem that has bothered me for a long time is, how can I use the String parameter key, to access the structure's property (the appropriate URL to the key).

Swift

259

Posted by

reepic

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Answer 1

One possible solution would be using KeyPath for the parameter key:

Code Block func loadGmailApiUrl(forKey key: KeyPath<GmailApiLibrary, URL>) -> URL? {
    guard let encodedValue = defaults.object(forKey: "gmailApiLibrary") as? Data else {
        print("No value for 'gmailApiLibrary'")
        return nil
    }
    do {
        let decodedValue = try JSONDecoder().decode(GmailApiLibrary.self, from: encodedValue)
        return decodedValue[keyPath: key]
    } catch {
        print(error)
        return nil
    }
}

Posted by

OOPer

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Answer 2

@OOPer, Thanks, I'm going to have a try.

And, I'm not sure. Maybe it's better to save the url stuff as dictionary, not structure?

Posted by

reepic

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Answer 3

Maybe it's better to save the url stuff as dictionary, not structure?

True. If you have some reason to use String key, it definitely is the better.

Posted by

OOPer

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In a method, how to access a structure's property with String parameter in dot syntax way

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