Issue raised, while retriving datas from JSON by u

I am retrieving datas from JSON by using swift. I am new to JSON. I don't how to retrieve this nested values. My JSON format is below.

//JSON DATA
{
    "data": [
        {
            "category_id": 1,
            "category_name": "category1",
            "category_icon": "",
            "category_child": [
                {
                    "sub_category_id": 11,
                    "sub_category_name": "subcategoryname1",
                    "sub_category_icon": ""
                },
                {
                    "sub_category_id": 12,
                    "sub_category_name": "subcategoryname2",
                    "sub_category_icon": ""
                }
            ]
        },
        {
            "category_id": 2,
            "category_name": "category2",
            "category_icon": "",
            "category_child": [
                {
                    "sub_category_id": 21,
                    "sub_category_name": "subcategoryname12",
                    "sub_category_icon": ""
                },
                {
                    "sub_category_id": 22,
                    "sub_category_name": "subcategoryname22",
                    "sub_category_icon": ""
                }
            ]
        }
    ]
}

I have tried some ways. But, I failed to get proper elements in dictionary. My code is below:

ATTEPMT 1:
var dict: NSDictionary! = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary

        for(var i = 0; i < (dict.valueForKey("data") as NSArray).count; i++)
        {
            self.categFromJson.addObject((dict.valueForKey("data") as NSArray) .objectAtIndex(i))

        }

        for(var i = 0; i < (categFromJson.valueForKey("category_child") as NSArray).count; i++)
        {
            self.sub_ct_FromArr.addObject((categFromJson.valueForKey("category_child") as NSArray) .objectAtIndex(i))

        }

        for(var i = 0; i < (sub_ct_FromArr.valueForKey("sub_category_name") as NSArray).count; i++)
        {
            self.sub_ct_name_arr.addObject((sub_ct_FromArr.valueForKey("sub_category_name") as NSArray) .objectAtIndex(i))

        }


//ATTEMPT 2
var dict: NSDictionary! = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary

for(var i = 0; i < (dict.valueForKey("data") as NSArray).count; i++)
{
    categFromJson.addObject((dict.valueForKey("data") as NSArray) .objectAtIndex(i))

    sub_ct_FromArr.addObject((categFromJson.valueForKey("category_child") as NSArray) .objectAtIndex(i))

    sub_ct_name_arr.addObject((sub_ct_FromArr.valueForKey("sub_category_name") as NSArray) .objectAtIndex(i))
}

But, for both attempt, final output is wrong and same. Bcos, coding below.

//CODING
println(sub_ct_name_arr.objectAtIndex(0))

//Output for this Code
(subcategoryname1,subcategoryname2)
//REQUIRED Output
subcategoryname1

Kindly guide me. I don't know what is that issue.

First, it's important to visualize what kind of data you have.

Then you can get root objects like this, following which object is of which type:

let dict = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as! NSDictionary

let dataArray = dict["data"] as! [[String:AnyObject]]  // The array of dictionaries

for object in dataArray {
    let category_id = object["category_id"] as! Int
    let category_name = object["category_name"] as! String
    // etc
    let category_child = object["category_child"] as! [[String:AnyObject]]
    for child in category_child {
        let sub_category_id = child["sub_category_id"] as! Int
        let sub_category_name = child["sub_category_name"] as! String
        println(sub_category_id)
        println(sub_category_name)
    }
}

You also might consider using a library like SwiftyJSON if you have a lot of decoding to do.