How to parse JSON data from local JSON File swift 3?

Question

I am trying to print a list of currencies and their symbols from a JSON file that I have locally in the project

guard let path: String = Bundle.main.path(forResource: "Common-Currency", ofType: "json") else {return}
    let url = URL(fileURLWithPath: path)

    do {
        let jsonData = try Data(contentsOf: url)
        let json = try JSONSerialization.jsonObject(with: jsonData, options: .mutableContainers)
        print(json)

        guard let jsonArray = json as? [Any] else { return }

        for currency in jsonArray {
            guard let eachCurrency = currency as? [String: Any] else {return}
            guard let currencyName = eachCurrency["code"] else {return}
            guard let currencySymbol = eachCurrency["symbol_native"] else {return}

            print(currencyName)
            print(currencySymbol)
        }
    }
    catch {
        print(error)
    }

This is the current code I have, however when I run it only the print(json) command gets executed, not the other 2 prints. What am I doing wrong?

The json looks something like this:

{

"Currencies" : {
"USD": {
    "symbol": "$",
    "name": "US Dollar",
    "symbol_native": "US$",
    "decimal_digits": 2,
    "rounding": 0,
    "code": "USD",
    "name_plural": "US dollars"
},
"CAD": {
    "symbol": "CA$",
    "name": "Canadian Dollar",
    "symbol_native": "CA$",
    "decimal_digits": 2,
    "rounding": 0,
    "code": "CAD",
    "name_plural": "Canadian dollars"
},
"EUR": {
    "symbol": "€",
    "name": "Euro",
    "symbol_native": "€",
    "decimal_digits": 2,
    "rounding": 0,
    "code": "EUR",
    "name_plural": "euros"
},
"AED": {
    "symbol": "AED",
    "name": "United Arab Emirates Dirham",
    "symbol_native": "د.إ.‏",
    "decimal_digits": 2,
    "rounding": 0,
    "code": "AED",
    "name_plural": "UAE dirhams"
},
"AFN": {
    "symbol": "Af",
    "name": "Afghan Afghani",
    "symbol_native": "؋",
    "decimal_digits": 0,
    "rounding": 0,
    "code": "AFN",
    "name_plural": "Afghan Afghanis"
},

Please post the beginning of the JSON string. json is most likely a dictionary. And if the file is in the bundle you don't need all guard expressions and optional bindings. Force unwrap all dictionary values. If the code crashes it's a design error. — vadian
– vadian, Commented Aug 18, 2017 at 8:33

vadian · Accepted Answer · 2017-08-18 09:12:02Z

1

The root object is a dictionary [String:Any]. The currencies are the value for key currencies which is also a dictionary.

You get the currency information with

let url = Bundle.main.url(forResource: "Common-Currency", withExtension: "json")!
do {
    let jsonData = try Data(contentsOf: url)
    let json = try JSONSerialization.jsonObject(with: jsonData) as! [String:Any]
    print(json)

    let currencies = json["Currencies"] as! [String: [String:Any]]

    for (key, currency) in currencies {
        let currencyName = currency["name"] as! String
        let currencySymbol = currency["symbol_native"] as! String

        print(key) // == `code`
        print(currencyName)
        print(currencySymbol)
    }
}
catch {
    print(error)
}

For an alphabetical order you have to get the keys, sort them and get the currency dictionary by key.

        let currencies = json["Currencies"] as! [String: [String:Any]]
        let currencyCodes = currencies.keys.sorted()

        for code in currencyCodes {
            let currency = currencies[code]!
            let currencyName = currency["name"] as! String
            let currencySymbol = currency["symbol_native"] as! String

            print(code)
            print(currencyName)
            print(currencySymbol)
        }

edited Aug 18, 2017 at 9:12

answered Aug 18, 2017 at 8:49

vadian

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6 Comments

A. G Over a year ago

Sorry, at this line of code : "let currencies = json["currencies"] as! [String: [String:Any]]" I get a Thread 1 EXC_BAD_INSTRUCTION error

vadian Over a year ago

The key starts with capital C. I edited the answer.

A. G Over a year ago

Thanks, worked like a charm. Also, do you have any idea why it doesn't print in order?

vadian Over a year ago

Because a dictionary is unordered by definition. I updated the answer with an ordered solution.

A. G Over a year ago

Also, how would I display these results in a table as the variables are not global and can't be used in other methods?

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