Why can't I decode my JSON file in Swift?

Question

I broke my original JSON file up into two different JSON files, but now I can't decode the second one. I've run it through multiple validators and it seems to be valid JSON, and I tried making certain properties optional, but to no avail.

Here's the extension I'm using to decode, which works for the first file, but crashes for the second one with the message "Thread 1: Fatal error: Failed to decode justiceforvictims.json from bundle."

    import UIKit

extension Bundle {
func decode<T: Decodable>(_ type: T.Type, from file: String) -> T {
    guard let url = self.url(forResource: file, withExtension: nil) else {
        fatalError("Failed to locate \(file) in bundle.")
    }

    guard let data = try? Data(contentsOf: url) else {
        fatalError("Failed to load \(file) from bundle.")
    }

    let decoder = JSONDecoder()

    guard let loaded = try? decoder.decode(T.self, from: data) else {
        fatalError("Failed to decode \(file) from bundle.")
    }

    return loaded
}
}

These are the structs describing the JSON files:

    struct petitionLabel: Codable, Identifiable {
    var id: String
    var name: String
    var items: [petitionName]
}

struct petitionName: Codable, Equatable, Identifiable {
    var id: String
    var name: String
    var link: String
    var organization: String?
    var justiceForVictims: Bool
    var policyReform: Bool
    var description: String?

#if DEBUG
static let example = petitionName(id: "45", name: "Hi", link: "bye", organization: "6", justiceForVictims: true, policyReform: false, description: "HI")
#endif
}

I'm calling the separate files like this:

     let petitionlabelPolicyReform = Bundle.main.decode([petitionLabel].self, from: "petitions.json")
let petitionlabelJusticeForVictims = Bundle.main.decode([petitionLabel].self, from: "justiceforvictims.json")

This is the malfunctioning JSON file:

{
"id": "DE58CEFF-7023-4B60-88CC-80C5B7BFB6EC",
"name": "Justice for Victims",
"items": [
    {
        "id": "D44AAEBC-BF4F-42CD-8C37-0FEF772A5B69",
        "name": "Justice for Breonna Taylor",
        "link": "https://act.colorofchange.org/sign/justiceforbre-breonna-taylor-officers-fired",
        "organization": "Color of Change",
        "justiceForVictims": true,
        "policyReform": false,
        "description": "Hi"
    },
    {
        "id": "82B28AFF-BB29-4186-AA07-04959180D81A",
        "name": "Justice for Ahmaud Arbery",
        "link": "https://change.org/p/federal-bureau-of-investigation-disbarment-of-george-e-barnhill",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": "Disbar prosecutor George E. Barnhill for his decision to sit on the case of Ahmaud Arbery's murder for three months out of prejudice/racism and a personal relationship with the murderers."
    },
    {
        "id": "71B872F2-3B5D-46D0-9D98-E696B4AE30E4",
        "name": "Justice for Regis Korchinski-Paquet",
        "link": "https://change.org/p/justice-for-regis-korchinski-paquet",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": "Hold the officers involved accountable in the death of Regis Korchinski-Paquet through firing and filing charges."
    },
    {
        "id": "71B872F2-3B5D-4",
        "name": "Justice for Emerald Black",
        "link": "https://www.change.org/p/san-leandro-police-deartment-justice-for-emerald-black",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B872F2-3B5D-46",
        "name": "Justice for Tete Gulley",
        "link": "http://chng.it/44DyFp8kdv",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B87",
        "name": "Justice for Tamir Rice",
        "link": "http://chng.it/sZkTD8tQbb",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B872F",
        "name": "Justice for Chrystul Kizer",
        "link": "http://chng.it/kMVf2HnDkb",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B872F2-3B",
        "name": "Justice for Alejandro Vargas Martinez",
        "link": "http://chng.it/q9BwVvN6ZX",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B87534B",
        "name": "Justice for Jennifer Jeffley",
        "link": "http://chng.it/QNGzSzmzxr",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B872F4q35B",
        "name": "Justice for Young Uwa",
        "link": "http://chng.it/KG2Xd46gV4",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B87349",
        "name": "Justice for Belly Mujinga",
        "link": "http://chng.it/TBfm476Ysj",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B872F3425B",
        "name": "Justice for Jamee Johnson",
        "link": "https://campaigns.organizefor.org/petitions/justice-for-jamee-johnson",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B872253F23B",
        "name": "Justice for Collins Khosa",
        "link": "http://chng.it/TCsXxK5hkF",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B879002F2B",
        "name": "Justice for Cameron Green",
        "link": "http://chng.it/2tpznJ9btJ",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "711230jB",
        "name": "Justice for Sean Reed",
        "link": "http://chng.it/nV9KQGSxfc",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71B872F2kfsd-3B",
        "name": "Justice for Joao Pedro",
        "link": "http://chng.it/FjJ7ZD4q5p",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "7kjlfgas1B872F2-3B",
        "name": "Justice for Willie Simmons",
        "link": "https://www.change.org/p/alabama-governor-kay-ivey-willie-simmons-has-served-38-years-for-a-9-robberyf",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "7B872Fkdfsg2-3B",
        "name": "Justice for Kendrick Johnson",
        "link": "https://www.change.org/p/united-states-supreme-court-justice-for-kendrick-johnson",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "7gijsa",
        "name": "Free Kyjuanzi Harris",
        "link": "https://www.change.org/p/illinois-governor-correcting-a-wrongful-conviction-kyjuanzi-harris",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "7aglkjB",
        "name": "Justice for Darrius Stewart",
        "link": "https://www.change.org/p/donald-j-trump-justice-for-darrius-stewart",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "71Bgsfklj3B",
        "name": "Justice for Andile Mchunu",
        "link": "https://www.change.org/p/bheki-cele-justice-for-andile-mchunu-bobo",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "7sdfgjkl1",
        "name": "Justice for Amiya Braxton",
        "link": "https://www.change.org/p/bre-jackson-justice-for-amiya-braxton",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "7thooos1",
        "name": "Justice for Eric Riddick",
        "link": "https://www.change.org/p/free-eric-riddick",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "rkjsgf",
        "name": "Justice for Elijah Nichols",
        "link": "https://www.change.org/p/ralph-s-northam-justice-for-elijah-nichols",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "ekas",
        "name": "Justice for Zinedine Karabo Gioia",
        "link": "https://www.change.org/p/the-botswana-government-justice-for-zinedine",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "rjkgsd1",
        "name": "Retrial for Angel Bumpass",
        "link": "https://www.change.org/p/bill-lee-demand-a-retrial-for-angel-bumpass-wrongfully-convicted-13-year-old-with-a-life-sentence",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "lkjas1",
        "name": "Justice for Sheku Bayoh",
        "link": "https://www.change.org/p/police-scotland-investigate-the-death-of-sheku-bayoh-in-police-custody",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "kadgskjldx",
        "name": "Free Albert Wilson",
        "link": "https://www.change.org/p/everybody-free-albert-wilson-from-the-crooked-kansas-legal-system",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "fjdiobs",
        "name": "Justice for Amari Boone",
        "link": "https://www.change.org/p/greg-abbott-justice-for-amari-boone",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "34asklj",
        "name": "Justice for Rashad Cunningham",
        "link": "https://www.change.org/p/fox-news-justice-for-rashad-cunningham-%EF%B8%8F",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "34jklasf",
        "name": "Justice for Tazne Vank Wyk",
        "link": "https://www.change.org/p/goodwood-magistrate-s-court-justice-for-tazne-van-wyk",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "3gjkaf4",
        "name": "Free Marshae Jones",
        "link": "https://www.change.org/p/pleasant-grove-police-department-dismiss-the-charges-on-marshae-jones-and-charge-the-one-who-shot-her-and-her-unborn-babyF",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "3agkjfn4",
        "name": "Justice for Michael Dean",
        "link": "https://www.change.org/p/temple-police-department-justice-for-michael-dean",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "3kgraljn4",
        "name": "Justice for Dion Johnson",
        "link": "https://www.change.org/p/phoenix-police-department-justice-for-dion-johnson",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "3jgakbfn4",
        "name": "Justice for Tamla Horsford",
        "link": "https://www.change.org/p/state-of-georgia-fire-sheriff-ron-freeman-stop-his-corruption-and-constant-cover-ups-as-sheriff-in-forsyth-count",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "3agllll4",
        "name": "Justice for Shukri Abdi",
        "link": "https://www.change.org/p/manchester-police-justice-for-shukri-abdi",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "3rasthe",
        "name": "Free Chaffin Darnel",
        "link": "https://www.change.org/p/everyone-and-the-police-of-cooks-county-illinois-free-chaffin-darnel-y",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "34t3409etj",
        "name": "Justice for Cariol Horne",
        "link": "https://www.change.org/p/nys-comptroller-thomas-p-dinapoli-support-former-buffaloe-police-officer-cariol-horne-to-receive-her-pension-a7acf769-f001-4a37-8fcc-558023abc33a",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "33c094",
        "name": "Justice for Brittany Williams",
        "link": "https://www.change.org/p/drop-false-charges-placed-on-police-brutality-victim-and-hold-the-officers-accountable",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "3j94g4",
        "name": "Justice for Quentin Suttles",
        "link": "https://www.change.org/p/john-j-flynn-consequences-for-excessive-force-used-on-quentin-suttles",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "8gkw47",
        "name": "Free Kenneth Reams",
        "link": "https://www.change.org/p/amnesty-international-free-kenneth-reams-he-s-been-on-death-row-for-the-past-26-years-he-never-killed-anybody",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "8lj7",
        "name": "Justice for James Scurlock",
        "link": "https://www.change.org/p/douglas-county-attorney-donald-kleine-demand-justice-for-james-scurlock-killed-by-omaha-racist-during-george-floyd-protest",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "8gh7",
        "name": "Justice for David McAtee",
        "link": "https://www.change.org/p/louisville-mayor-greg-fischer-justice-for-david-mcatee",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "8jgarl7",
        "name": "Justice for Ashton Dickson",
        "link": "https://www.change.org/p/mayor-of-ottawa-justice-for-ashton-dickson-he-was-killed-at-the-age-of-25-and-had-a-bright-future-ahead",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "8graijeo7",
        "name": "Free Anthony Wint",
        "link": "https://www.change.org/p/ron-desantis-free-anthony-wint-fbc27c7c-920d-4104-9960-a234f45cbe20",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "8iba7",
        "name": "Retrial for Sandra Bland",
        "link": "https://www.change.org/p/texas-governor-i-want-sandra-bland-s-case-reopened",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "9igrae0",
        "name": "Justice for Brad Levi",
        "link": "https://www.change.org/p/city-of-austin-texas-justice-for-brad-levi-ayala",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "9lkgjra0",
        "name": "Justice for Jonas Joseph",
        "link": "https://www.change.org/p/tampa-bay-justice-for-jonas-joseph",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "9afdgj0",
        "name": "Justice for Dominique Clayton",
        "link": "https://www.change.org/p/justice-for-dominique-clayton",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "90ntk0",
        "name": "Justice for Anderson Arboleda",
        "link": "https://www.change.org/p/fiscaliacol-justicia-para-anderson-arboleda-joven-afro-asesinado-a-golpes-por-un-polic%C3%ADa-en-el-cauca-justiciaparaandersonarboleda-policiacolombia-cgr-colombia-pgn-col-defensoriacol",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "9bej90",
        "name": "Free Curtis Price",
        "link": "https://www.change.org/p/governor-of-south-carolina-south-carolina-supreme-court-south-carolina-senators-free-curtis-price",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "90vw0",
        "name": "Justice for Crosley Green",
        "link": "https://www.change.org/p/grant-clemency-to-crosley-green-now",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    },
    {
        "id": "9b90ea0",
        "name": "Justice for Tyler J. Evans",
        "link": "https://www.change.org/p/columbia-county-jail-justice-for-tyler-j-evans",
        "organization": "Change.org",
        "justiceForVictims": true,
        "policyReform": false,
        "description": ""
    }
]
}

When decoding JSON with `JSONDecoder` never ignore the error with `try?`. Catch the error and `print` it. It tells you immediately what's wrong. The fatal error is useless. And name structs always with a starting uppercase letter. — vadian, Jun 16 '20 at 04:08

score 2 · Answer 1 · answered Jun 16 '20 at 02:48

The issue is your top level json type is an object of type petitionLabel rather than Array [petitionLabel]. So it's not issue of SwiftUI.

So you would need to change

let petitionlabelJusticeForVictims = Bundle.main.decode([petitionLabel].self, from: "justiceforvictims.json")

to

let petitionlabelJusticeForVictims = Bundle.main.decode(petitionLabel.self, from: "justiceforvictims.json")

As I do in this tested code in https://www.tutorialspoint.com/compile_swift_online.php

import Foundation
import Glibc

let str = """
{
"id": "DE58CEFF-7023-4B60-88CC-80C5B7BFB6EC",
"name": "Justice for Victims",
"items": [
    {
        "id": "D44AAEBC-BF4F-42CD-8C37-0FEF772A5B69",
        "name": "Justice for Breonna Taylor",
        "link": "https://act.colorofchange.org/sign/justiceforbre-breonna-taylor-officers-fired",
        "organization": "Color of Change",
        "justiceForVictims": true,
        "policyReform": false,
        "description": "Hi"
    }
]
}
"""

struct petitionLabel: Codable {
    var id: String
    var name: String
    var items: [petitionName]
}

struct petitionName: Codable {
    var id: String
    var name: String
    var link: String
    var organization: String?
    var justiceForVictims: Bool
    var policyReform: Bool
    var description: String?

#if DEBUG
static let example = petitionName(id: "45", name: "Hi", link: "bye", organization: "6", justiceForVictims: true, policyReform: false, description: "HI")
#endif
}

let json = try JSONDecoder().decode(petitionLabel.self, from: str.data(using: .utf8)!)

print(json)

For your convenience, it would be nice to catch JSONDecoder.decode throwing function error rather than silence it using try? so you can log the error. Actually, using try! can help you understand the error as Swift will report the error to you like this:

Fatal error: Error raised at top level: Swift.DecodingError.typeMismatch(Swift.Array<Any>, Swift.DecodingError.Context(codingPath: [], debugDescription: "Expected to decode Array<Any> but found a dictionary instead.", underlyingError: nil))

score 0 · Accepted Answer · answered Jun 17 '20 at 16:41

0

I just forgot to put brackets around the JSON lol

answered Jun 17 '20 at 16:41

Mira

131
1
9

Why can't I decode my JSON file in Swift?

2 Answers2