Why Is an Object Not Being Decoded

Why is an object not being decoded?

according to your JSON - "type":"GET_HORSE" - you should change enum MessageType : Int,Decodable to enum MessageType: String, Decodable. I've checked your code after changes to a String and got correct model here

if let json = try? decoder.decode(Message<Horse>.self, from: data!) {
    print(json)
    print("something")
}

but it's not json, it's a model with Message<Horse> type

JSON Decoder cannot decode an object into an object

What did you expect to happen / get printed?

The log package (which uses the fmt package) prints structs enclosed in braces, listing field values separated by spaces.

Your MiddleMan has a single field, so it'll look like this:

{field}

Where field is another struct of type CompletedByUser, which has 2 fields, so it'll look like this:

{{field1 field2}}

Where field is of string type, being the empty string, so you'll see the value of field2 prefixed with a space:

{{ a03dfee5-a754-4eb9}}

If you print it adding field names:

log.Printf("%+v", middleMan)

You'll see an output like:

{User:{DisplayName: Id:a03dfee5-a754-4eb9}}

Using another (Go-syntax) format:

log.Printf("%#v", middleMan)

Output:

main.MiddleMan{User:main.CompletedByUser{DisplayName:"", Id:"a03dfee5-a754-4eb9"}}

Try this on the Go Playground.

Why is my object of type SKTileMapNode not being decoded?

For anyone who runs into this issue, I spent the better part of a day figuring it out and found no luck. However, I figured out that the larger issue was found in my SKScene. My custom class was encoded and decoded as part of the scene. The solution was to use NSKeyedArchiver on my scene as follows:

override func encodeRestorableState(with coder: NSCoder) {
    self.sceneWasSaved = true
    if self.gameState != nil {
        coder.encode(self.sceneWasSaved, forKey: "GameViewController_sceneWasSaved")
        coder.encode(self.gameState!, forKey: "GameViewController_gameState")
        NSKeyedArchiver.archiveRootObject(self.gameScene!, toFile: filePath)
    }
    super.encodeRestorableState(with: coder)
}

Then unarchive:

vc.gameScene = NSKeyedUnarchiver.unarchiveObject(withFile: filePath) as? GameScene

It seems that if we use the coder and decoder that Spritekit types are not properly handled for whatever odd reason. But if you use the archiver method it handles them and both my SKScene and my custom class was properly encoded and decoded.

Note I changed nothing in my custom class described in the question, only the archiving of SKScene.

Anyway, I don't have an answer of why this works, but maybe it will save someone!

str' object has no attribute 'decode'. Python 3 error?

You are trying to decode an object that is already decoded. You have a str, there is no need to decode from UTF-8 anymore.

Simply drop the .decode('utf-8') part:

header_data = data[1][0][1]

As for your fetch() call, you are explicitly asking for just the first message. Use a range if you want to retrieve more messages. See the documentation:

The message_set options to commands below is a string specifying one or more messages to be acted upon. It may be a simple message number ('1'), a range of message numbers ('2:4'), or a group of non-contiguous ranges separated by commas ('1:3,6:9'). A range can contain an asterisk to indicate an infinite upper bound ('3:*').

why Decode method in swift4 gives object nil if there is one tag in json payload has type mismatch

Please read the error message carefully, the reason is very clear (no need to guess)

Expected String but Int has been found

means the (found) value is Int but you declared a String property

All strings in JSON are wrapped in double quotes, the type for type is Int

class Animal: Codable {
    var name: String?
    var type: Int?
}

If the JSON contains always both values declare the properties as non-optional by removing the question marks.

The implicit decoder / initializer fails if any error occurs, you can see this just from the code syntax. If you want to have finer control write your own custom initializer.

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