Problem converting JSON to Array with Swift

Question

I try to convert a JSON to an Array but I face some issue and do not know how to sort it out. I use Swift 5 and Xcode 12.2.

Here is the JSON from my PHP query:

    [
            {
            Crewcode = AAA;
            Phone = 5553216789;
            Firstname = Philip;
            Lastname = MILLER;
            email = "[email protected]";
        },
            {
            Crewcode = BBB;
            Phone = 5557861243;
            Firstname = Andrew;
            Lastname = DEAN;
            email = "[email protected]";
        }
    ]

And here is my Swift code :

    let url: URL = URL(string: "https://xxx.php")!

    let defaultSession = Foundation.URLSession(configuration: URLSessionConfiguration.default)

    let task = defaultSession.dataTask(with: url) { (data, response, error) in

        if error != nil {
            print("Failed to download data")
        }
        else {
            print("Data downloaded")

            do {
                if let jsondata = (try? JSONSerialization.jsonObject(with: data!, options: [])) {
                    
                    print(jsondata)

                    struct Crew: Decodable {
                        var Code: String
                        var Phone: String
                        var Firstname: String
                        var Lastname: String
                        var email: String
                    }

                    let decoder = JSONDecoder()
                    do {
                        let people = try decoder.decode([Crew].self, from: jsondata as! Data)
                        print(people)
                    }
                    catch {
                        print(error)
                    }
                }
            }
        }
    }
    
    task.resume()

When I run my code I get the following error:

Could not cast value of type '__NSArrayI' (0x7fff86b930b0) to 'NSData' (0x7fff86b911e8). 2020-12-09 14:52:48.988468+0100 FTL[57659:3019805] Could not cast value of type '__NSArrayI' (0x7fff86b930b0) to 'NSData' (0x7fff86b911e8). Could not cast value of type '__NSArrayI' (0x7fff86b930b0) to 'NSData' (0x7fff86b911e8).

Should you have any idea to get it right, I thank you in advance for your assistance on this !

You're mixing JSONSerialization with JSONDecoder. These are not related (the former is a long-existing ObjC system; the latter is a newer Swift system). JSONDecoder expects you to pass the actual data to it. Remove the JSONSerialization code. But note that your struct requires that there be a Code parameter that your JSON doesn't include. If it's optional, then you need to make it optional (String?). — Rob Napier
– Rob Napier, Commented Dec 9, 2020 at 20:22

vadian · Accepted Answer · 2020-12-09 20:36:38Z

1

You are deserializing the JSON twice by mixing up JSONSerialization and JSONDecoder.

Delete the first one

~~if let jsondata = (try? JSONSerialization.jsonObject(with: data!, options: [])) {~~

– By the way the JSON in the question is neither fish nor fowl, neither JSON nor an NS.. collection type dump –

and replace

let people = try decoder.decode([Crew].self, from: jsondata as! Data)

with

let people = try decoder.decode([Crew].self, from: data!)

and the struct member names must match the keys otherwise you have to add CodingKeys

edited Dec 9, 2020 at 20:36

answered Dec 9, 2020 at 20:25

vadian

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1 Comment

hgiraud Over a year ago

Thank you so much for your help! I tried and it works very well.

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