how to parse json data from local files?

Question

i am very new to json parsing and tried to parse a json file which has list of cars but when i do parse, it gives out nil

    func jsonTwo(){
    let url = Bundle.main.url(forResource: "car_list", withExtension: "json")!
    let data = try! Data(contentsOf: url)
    let JSON = try! JSONSerialization.jsonObject(with: data, options: []) as? [String : Any]
    print(".........." , JSON , ".......")
    let brand = JSON?["models"] as? [[String : Any]]
    print("=======",brand,"=======")
}

and when i made some modifications to this code as below

    func jsonTwo(){
    let url = Bundle.main.url(forResource: "car_list", withExtension: "json")!
    let data = try! Data(contentsOf: url)
    let JSON = try! JSONSerialization.jsonObject(with: data, options: []) 
    print(".........." , JSON , ".......")
    let brand = JSON["brand"] as? [[String : Any]]
    print("=======",brand,"=======")
}

then i get and error saying "Type 'Any' has no subscript members"

below is a sample of the json file that i am using

[{"brand": "Aston Martin", "models": ["DB11","Rapide","Vanquish","Vantage"]}]

Possible duplicate of [Reading in a JSON File Using Swift](https://stackoverflow.com/questions/24410881/reading-in-a-json-file-using-swift) — dahiya_boy, Jan 08 '19 at 10:22
You should use Codable for Swift 4. `try! JSONSerialization.jsonObject(with: data, options: []) ` returns `Any`. try try! JSONSerialization.jsonObject(with: data, options: []) as! [[String: AnyObject]]` — Scriptable, Jan 08 '19 at 10:22
please avoid `try!` as it may crash the app , also you should use `Codable` time for `JSONSerialization` is over — Shehata Gamal, Jan 08 '19 at 10:27

vadian · Answer 1 · 2019-01-08T10:31:23.763

The outer object is an array, please note the [] and the value for key models is a String array.

func jsonTwo() {
    let url = Bundle.main.url(forResource: "car_list", withExtension: "json")!
    let data = try! Data(contentsOf: url)
    let json = try! JSONSerialization.jsonObject(with: data) as! [[String : Any]]
    print(".........." , JSON , ".......")
    for item in json {
        let brand = item["brand"] as! String
        let models = item["models"] as! [String]
        print("=======",brand, models,"=======") 
    }
}

or more comfortable with Decodable

struct Car: Decodable {
    let brand : String
    let models : [String]
}

func jsonTwo() {
    let url = Bundle.main.url(forResource: "car_list", withExtension: "json")!
    let data = try! Data(contentsOf: url)
    let cars = try! JSONDecoder().decode([Car].self, from: data)
    for car in cars {
        let brand = car.brand
        let models = car.models
        print("=======",brand, models,"=======") 
    }
}

Normally you are strongly discouraged from force unwrapping optionals with ! but in this case the code must not crash because a file in the application bundle is read-only at runtime and any crash would reveal a design mistake.

Shehata Gamal · Answer 2 · 2019-01-08T10:28:09.993

7

You need

struct Root: Codable {
    let brand: String
    let models: [String]
}

do {

     let url = Bundle.main.url(forResource: "car_list", withExtension: "json")!
     let data = try Data(contentsOf: url) 
     let res = try JSONDecoder().decode([Root].self, from: data)
     print(res)

}
catch { 
    print(error)
}

Your problem as

let JSON = try! JSONSerialization.jsonObject(with: data, options: [])

returns Any , so you can't use subscript it like a dictionary here JSON["brand"]

edited Jan 08 '19 at 10:28

answered Jan 08 '19 at 10:22

Shehata Gamal

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you are a life saver – vgvishesh23113 Jan 08 '19 at 11:14

score 2 · Accepted Answer · answered Jan 08 '19 at 11:01

Please note that variable JSON in your code is an array of objects. You have to cast it properly.

func jsonTwo(){
    let url = Bundle.main.url(forResource: "car_list", withExtension: "json")!
    let data = try! Data(contentsOf: url)
    let JSON = try! JSONSerialization.jsonObject(with: data, options: []) 
    print(".........." , JSON , ".......")
    if let jsonArray = JSON as? [[String: Any]] {
        for item in jsonArray {
            let brand = item["brand"] as? String ?? "No Brand" //A default value
            print("=======",brand,"=======")
        }
    }
}

much appreciated , you are a savior – vgvishesh23113 Jan 08 '19 at 11:22 — vgvishesh23113, Jan 08 '19 at 11:22

how to parse json data from local files?

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