Making an api request using URLSession.shared.dataTask

Question

I'm making an api request:

var urlRaw = bookSummaryReadsDomainUrl + apiKey;
let url = URL(string: urlRaw.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)!)

let task = URLSession.shared.dataTask(with: url!, completionHandler: { (data, response, error) in
    if let error = error {
        print("Error with fetching book summary reads: \(error)")
        return
    }
    
    guard let httpResponse = response as? HTTPURLResponse,
        (200...299).contains(httpResponse.statusCode) else {
            print("Error with the response, unexpected status code: \(response)")
            return
    }
    if let data = data,
        let flurryItems = try? JSONDecoder().decode(FlurrySummary.self, from: data) {
        completionHandler(flurryItems.rows ?? [])
    }
})
task.resume()

to an endpoint that returns the following data

{
"rows": [
{
"dateTime": "2020-07-04 00:00:00.000-07:00",
"event|name": "BookSummaryRead",
"paramName|name": "bookId",
"paramValue|name": "elon-musk",
"count": 12
},

... ]

import Foundation

struct FlurrySummary: Codable {
    var rows: [FlurryItem]?
    enum CodingKeys: String, CodingKey {
        case rows = "rows"
    }
}


struct FlurryItem: Codable {
    var name: String?
    var event: String?
    var value: String?
    var count: String?
    var date: String?
    enum CodingKeys: String, CodingKey {
        case name = "paramName|name"
        case event = "event|name"
        case value = "paramValue|name"
        case count = "count"
        case date = "dateTime"
    }
}

For some reason the JSONDecoder.decode part is not working. It's not filling up the flurryItems and flurryItems.rows = nil. What am I doing wrong?

I’d suggest not using try? with the decode, because that discards any diagnostic error, if it failed. Use do-try-catch and see what error you get. — Rob
– Rob, Commented Jul 5, 2020 at 15:24
Btw you are abusing of the optionals. You should declare optional only the properties that might be nil not every property. You should declare your properties as constants. — Leo Dabus
– Leo Dabus, Commented Jul 5, 2020 at 15:26

Frankenstein · Accepted Answer · 2020-07-05 15:30:07Z

1

The property count in FlurryItem has to be of type Int.

var count: Int?

You have to catch the Error that are thrown.

do {
    if let data = data,
        let flurryItems = try JSONDecoder().decode(FlurrySummary.self, from: data) {
        completionHandler(flurryItems.rows ?? [])
    }
} catch { print(error) }

Also, you don't need the CodingKeys in FlurrySummary since the property name is the same.

struct FlurrySummary: Codable {
    var rows: [FlurryItem]?
}

Note: Also, avoid using optional declaration if the property never becomes null.

edited Jul 5, 2020 at 15:30

answered Jul 5, 2020 at 15:26

Frankenstein

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3 Comments

Leo Dabus Over a year ago

This will fix the error but code only answers are not helpful for future readers.

Leo Dabus Over a year ago

Btw does it need to be optional? Does it need to be a variable instead of a constant?

Leo Dabus Over a year ago

Are the Coding keys necessary for the root structure?

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