Deal with an API that changes format

Looking for a bit of advice. I'm tapping into WordsAPI to create a spellchecker iOS app using swift, however, depending on the words you search for the JSON response is sometimes in a different format.

Response for the word "test" looks like this (I've stripped out most of it just to get the point across)

{ 
    "word": "test", 
    "pronunciation": {
         "all": "tɛst"
    }
}

Whereas the response for the word "testing" looks like this

{ 
    "word": "testing", 
    "pronunciation": "'tɛstɪŋ" 
}

I'm using a model to decode the response data

struct WordDetails: Codable {
   let word: String
   let results: [Definition]
   let pronunciation: Pronounce
}

struct Pronounce: Codable {
   let all: String
}

struct Definition: Codable {
   let definition: String
   let partOfSpeech: String
   let synonyms: [String]?
}

But this will only deal with one scenario and fail to decode the other. Can I write it in such a way to deal with both formats?

You can implement the decoding yourself and try to decode pronunciation key as String type. If that fails with DecodingError.typeMismatch error you decode it as Pronounce type:

struct WordDetails: Codable {
    let word: String
    let results: [Definition]
    let pronunciation: Pronounce
    
    enum CodingKeys: String, CodingKey {
        case word
        case results
        case pronunciation
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        word = try container.decode(String.self, forKey: .word)
        results = try container.decode([Definition].self, forKey: .results)
        do {
            let string = try container.decode(String.self, forKey: .pronunciation)
            pronunciation = Pronounce(all: string)
        } catch DecodingError.typeMismatch {
            pronunciation = try container.decode(Pronounce.self, forKey: .pronunciation)
        }
    }
}