Converting JSON to array in Swift 2

Question

I need to build Arrays for a Grouped UITableView, with a Title and Detail line in each table cell. I've got my json output from the server putting it in the right shape to iterate through the UITableViewDataSource methods. But what's the simplest way to convert these to a readable array that those UITableView functions can reference?

The headings array is for the Group headings, so it's just a one-dimensional array. I can iterate that. The titles and details arrays are both two dimensional. I can't figure out how to do that in Swift.

"headings":["Tuesday, August 16, 2016","Wednesday, August 17, 2016","Thursday, August 18, 2016","Friday, August 19, 2016","Saturday, August 20, 2016","Sunday, August 21, 2016","Monday, August 22, 2016","Tuesday, August 23, 2016","Wednesday, August 24, 2016","Thursday, August 25, 2016","Friday, August 26, 2016","Saturday, August 27, 2016","Sunday, August 28, 2016","Monday, August 29, 2016","Tuesday, August 30, 2016","Wednesday, August 31, 2016","Thursday, September 1, 2016","Friday, September 2, 2016","Saturday, September 3, 2016","Sunday, September 4, 2016","Monday, September 5, 2016","Tuesday, September 6, 2016","Wednesday, September 7, 2016","Thursday, September 8, 2016","Friday, September 9, 2016","Saturday, September 10, 2016","Sunday, September 11, 2016","Monday, September 12, 2016","Tuesday, September 13, 2016","Wednesday, September 14, 2016","Thursday, September 15, 2016","Friday, September 16, 2016"],

"titles":[["Joe Johnson"],["Joe Johnson"],["Sandy Primmell","Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Sandy Primmell","Joe Johnson"],["Joe Johnson","Joe Johnson"],["Sandy Primmell","Joe Johnson"],["Mark Greene","Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Sandy Primmell","Joe Johnson"],["Joe Johnson"],["Sandy Primmell","Joe Johnson"],["Mark Greene","Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"],["Joe Johnson"]],

"details":[["OFF"],["OFF"],["Gregory","OFF"],["Gregory"],["OFF"],["OFF"],["OFF"],["Weekday Rounders","OFF"],["Weekday Rounders","Night Owls"],["Gregory","OFF"],["Gregory","OFF"],["OFF"],["OFF"],["OFF"],["Gregory"],["Gregory","OFF"],["Gregory"],["Gregory","OFF"],["Gregory","OFF"],["OFF"],["OFF"],["OFF"],["OFF"],["OFF"],["OFF"],["OFF"],["OFF"],["OFF"],["OFF"],["OFF"],["OFF"],["OFF"]]

UPDATE

Here's my Alamofire async function that grabs the data:

manager.request(.POST, getRouter(), parameters:["dev": 1, "app_action": "schedule", "type":getScheduleType(), "days_off":getScheduleDaysOff(), "period":getSchedulePeriod(), "begin_date":getScheduleBeginDate(), "end_date":getScheduleEndDate()])
        .responseString {response in
            print(response)
            var json = JSON(response.result.value!);
// what I'm missing
   }

how did you get that data from server? some framework have built in JSON parser that will allow you to easily create those array — Lope
– Lope, Commented Aug 16, 2016 at 12:18
@Thom try my answer and let me know if you have some problems — Marco Santarossa
– Marco Santarossa, Commented Aug 16, 2016 at 12:20
@Thom ok, if it works for you mark my answer as right, I would appreciate it, thank you — Marco Santarossa
– Marco Santarossa, Commented Aug 16, 2016 at 12:22

Marco Santarossa · Accepted Answer · 2016-08-17 12:55:21Z

4

You can use this function:

func convertStringToDictionary(text: String) -> [String:AnyObject]? {
    if let data = text.dataUsingEncodi‌ng(NSUTF8StringEncodi‌ng) {
        do {
            return try NSJSONSerialization.JSONObjectWithData(data, options: []) as? [String:AnyObject]
        } catch let error as NSError {
            print(error)
        }
    }
    return nil
}

and then you can read the array like this:

if let dict = convertStringToDictionary(jsonText) {
    let array = dict["headings"] as? [String]
}

edited Aug 17, 2016 at 12:55

answered Aug 16, 2016 at 12:18

Marco Santarossa

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6 Comments

Works for a Living Over a year ago

I put the function into a Swift file and it gave me two errors: On line 2: Value of type 'String' has no member 'data' On line 4: Use of unresolved identifier 'JSONSerialization'

Marco Santarossa Over a year ago

@Thom try this: let data = text.dataUsingEncoding(NSUTF8StringEncoding)

Works for a Living Over a year ago

That fixed the first error. Still getting the one on line 4.

Marco Santarossa Over a year ago

@Thom replace JSONSerialization with NSJSONSerialization

Works for a Living Over a year ago

I tried that but then it said that jsonObject is not a member of NSJSONSerialization

|

Ahmad Baracat · Accepted Answer · 2016-08-16 12:49:26Z

2

Alternatively, You can use JSON parsing libraries like Argo or SwiftyJSON, which were created to simplify the JSON parsing. They are both well tested and will handle edge cases for you, like missing parameters in the JSON responses etc.

An example using Argo:

Assuming the JSON response has this format (from Twitter API)

{
  "users": [
    {
      "id": 2960784075,
      "id_str": "2960784075",
      ...
    }
}

1- Create a Swift class to represent the response

Note that Response is a class that contains an array of User which is another class not shown here, but you get the point.

struct Response: Decodable {
    let users: [User]
    let next_cursor_str: String

    static func decode(j: JSON) -> Decoded<Response> {
        return curry(Response.init)
            <^> j <|| "users"
            <*> j <| "next_cursor_str"
    }
}

2- Parse the JSON

//Convert json String to foundation object
let json: AnyObject? = try? NSJSONSerialization.JSONObjectWithData(data, options: [])

//Check for nil    
if let j: AnyObject = json {
  //Map the foundation object to Response object
  let response: Response? = decode(j)
}

An example using Swifty

As explained in the official documentation:

1- Convert JSON string to SwiftyJSON object

if let dataFromString = jsonString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false) {
    let json = JSON(data: dataFromString)
}

2- Access specific element

If data is an array then use the index

//Getting a double from a JSON Array
let name = json[0].double

If data is a dictionary then use the key

//Getting a string from a JSON Dictionary
let name = json["name"].stringValue

2'- Loop over the elements

Array

//If json is .Array
//The `index` is 0..<json.count's string value
for (index,subJson):(String, JSON) in json {
    //Do something you want
}

Dictionary

//If json is .Dictionary
for (key,subJson):(String, JSON) in json {
   //Do something you want
}

edited Aug 16, 2016 at 12:49

answered Aug 16, 2016 at 12:28

Ahmad Baracat

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4 Comments

Works for a Living Over a year ago

Thanks. How about with Swifty? I looked there but couldn't successfully implement anything.

Ahmad Baracat Over a year ago

@Thom Referenced the important pieces from the documentation. Notice that with Argo you create a class and then let Argo map the JSON data to your class, but in Swifty, you don't create a class, but you do the mapping yourself.

Works for a Living Over a year ago

This is terrific. Thank you. I am using SwiftyJson and was able to use it to iterate through the one-dimensional one no problem. Is a dictionary basically the JS object equiv?

Ahmad Baracat Over a year ago

You mean equivalent to the JS dictionary? Yes, it is :)

Bashta · Accepted Answer · 2016-08-16 12:48:46Z

2

I would suggest using AlamofireObjectMapper. The library lets you you map objects from json easily and if combined with Alamofire can cast and return your object on the server response. The object mapping itself should look like this in your case

class CustomResponseClass: Mappable {
    var headings: [String]?

    required init?(_ map: Map){

    }

    func mapping(map: Map) {
        headings <- map["headings"]
   }
}

This way you decouple the logic of mapping and parsing json from your tableViewController.

AlamofireObjectMapper

edited Aug 16, 2016 at 12:48

answered Aug 16, 2016 at 12:43

Bashta

8510 bronze badges

3 Comments

Works for a Living Over a year ago

Thanks. Checking this out.

Bashta Over a year ago

@Thom In case you found your solution can you please accept one of the above answers please.

Works for a Living Over a year ago

I used bits and pieces from multiple answers but I chose the one that I think was the closest to my final solution.

Nirav D · Accepted Answer · 2016-08-16 13:48:46Z

2

Looks like you are getting Dictionary from json and each key contain Array, you can try something like this, first declare one Dictionary instance and use that with TableViewDataSource methods.

var response = [String: AnyObject]()

do {
     self.response = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableContainers) as! [String: AnyObject]
     print(dic)
}
catch let e as NSError {
     print(e.localizedDescription)
}

Now inside tableView methods

func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    if let arr = self.response["headings"] as? [String] {
        return arr.count
    }
    return 0
}

func tableView(tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
    let headings = self.response["headings"] as! [String]
    return headings[Int]
}

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    if let arr = self.response["titles"] as? [[String]] {
        return arr[Int].count
    }
    return 0
}

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let titles = self.response["titles"] as! [[String]]
    let details = self.response["details"] as! [[String]]       
    let cell = tableView.dequeueReusableCellWithIdentifier("cell") as! EmployeeCell
    cell.mainLabel?.text = titles[indexPath.section][indexPath.row]
    cell.detailLabel?.text = details[indexPath.section][indexPath.row]
    return cell
}

edited Aug 16, 2016 at 13:48

answered Aug 16, 2016 at 12:28

Nirav D

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11 Comments

Works for a Living Over a year ago

What am I putting in data!? I'm getting errors in your do/catch.

Nirav D Over a year ago

In your api call you are getting NSData object, that you need to pass with that method, If you don't get it add the code in question that you have used to call api.

Nirav D Over a year ago

after this line var json = JSON(response.result.value!); add line like this self.response = json as! [String: AnyObject]` and then reload the tableView.

Nirav D Over a year ago

Have you try like i said?

Works for a Living Over a year ago

Are you saying that I don't need the do/catch?

|

Collectives™ on Stack Overflow

Converting JSON to array in Swift 2

4 Answers 4

6 Comments

An example using Argo:

1- Create a Swift class to represent the response

2- Parse the JSON

An example using Swifty

1- Convert JSON string to SwiftyJSON object

2- Access specific element

2'- Loop over the elements

4 Comments

3 Comments

11 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

6 Comments

An example using Argo:

1- Create a Swift class to represent the response

2- Parse the JSON

An example using Swifty

1- Convert JSON string to SwiftyJSON object

2- Access specific element

2'- Loop over the elements

4 Comments

3 Comments

11 Comments

Your Answer

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