Using Coding Keys to exclude values from being decoded

Question

I have the following structure to decode JSON data:

UPDATED:

struct Section {
    let owner : String
    var items : [ValueVariables]
}

struct ValueVariables : Decodable {
    var isSelected = false
    let breed: String
    let color: String
    let tagNum: Int

    // other members 
}

The issue is isSelected is not a value being decoded, how can I exclude it from being decoded to prevent it from causing an error like this:

keyNotFound(CodingKeys(stringValue: "isSelected", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: \"isSelected\", intValue: nil) (\"isSelected\"), converted to is_selected.", underlyingError: nil))

I have tried using coding keys like this, but it does not seem to work :

private enum CodingKeys : String, CodingKey {
    case isSelected = "isSelected"
}

Applied Answer:

struct ValueVariables : Decodable {

    private enum CodingKeys : String, CodingKey {
        case breed, color, tagNum
    }

    var isSelected = false
    let breed: String
    let color: String
    let tagNum: Int
}

The JSON Looks like this:

[{"breed":"dog","color":"black","tagNum":20394}]

Error recieved:

Type 'ValueVariables' does not conform to protocol 'Decodable'

isSelected is a computed var? Is it a var for UI? Then don't mix like that your "data model" and a ui-model. Is it an addon? — Larme, Sep 16 '19 at 14:49
Your latest version of the posted code does _not_ generate an error. If your own code is different and generates an error you need to tell us but to me this question has been already correctly answered. — Joakim Danielson, Sep 16 '19 at 15:39

vadian · Accepted Answer · 2019-09-16T15:15:20.793

4

The other way round, you have to specify all keys which are going to be decoded.

struct ValueVariables : Decodable {

    private enum CodingKeys : String, CodingKey {
        case breed, color
    }

    var isSelected = false
    let breed: String
    let color: String
}

edited Sep 16 '19 at 15:15

answered Sep 16 '19 at 14:39

vadian

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In addition to case `isSelected = "isSelected"`? – John Sep 16 '19 at 14:42
2

No, **omit** the excluded keys – vadian Sep 16 '19 at 14:43
What if color is a Int not a String, how would the CodingKeys be different? – John Sep 16 '19 at 14:45
`color` is always a string even if the **value** is `Int`. – vadian Sep 16 '19 at 14:49
I am still getting the same error, the Coding Keys do not seem to help – John Sep 16 '19 at 15:06
Is there something I need to change in `struct ValueVariables : Decodable {` ? – John Sep 16 '19 at 15:10
I updated the answer. The JSON `{"breed":"dog","color":"black"}` will be decoded correctly. – vadian Sep 16 '19 at 15:17
Now I get the error: `Type 'ValueVariable' does not conform to protocol 'Decodable'` – John Sep 16 '19 at 15:17
Please edit your question and add the **entire** struct. – vadian Sep 16 '19 at 15:19
You have to add `tagNum` to the CodingKeys. Please read my answer carefully. – vadian Sep 16 '19 at 15:24
`tagNum` is in the CodingKeys I was just shortening the struct for the question, please see the update I posted with the full struct and JSON. I still get the error does not conform to protocol 'Decodable' – John Sep 16 '19 at 15:30
That's impossible if you decode `JSONDecoder().decode([ValueVariables].self, from:...` – vadian Sep 16 '19 at 15:32
I believe I am doing it correctly as the following: `try decoder.decode([ValueVariables].self` please see my update – John Sep 16 '19 at 16:06
The struct, the code and the JSON in the question do work. – vadian Sep 16 '19 at 16:16

Using Coding Keys to exclude values from being decoded

1 Answers1