Looping through embedded JSON arrays in Swift?

Question

I'm trying to loop through an embedded JSON array and extract all the values to put in a local array. This is what the JSON looks like:

"welcome": {
  "data": {
    "tncUrl": ""
  },
  "items": [
    {
      "newUser": [
        {
          "stepConcept": false
        },
        {
          "stepSafety": true
        },
        {
          "stepFacilitator": true
        },
        {
          "stepTransparency": true
        }
      ],
      "switcher": [
        {
          "stepConcept": true
        },
        {
          "stepSafety": true
        },
        {
          "stepFacilitator": true
        },
        {
          "stepTransparency": true
        }
      ]
    }
  ]
}

I'm able to get to a point where I can see I'm retrieving values for "newUser", the problem is looping through those values and adding them to an array. I'm getting a EXC_BAD_INSTRUCTION error when doing so. This is the code I'm using to get those values:

  func prepareArrayOfViews(userType: User)
    {
        if (welcomeJSON != nil)
        {
            let items : NSArray? = welcomeJSON!.value(forKey: "items") as? NSArray

            if (items == nil)
            {
                listOfViews = ["stepConcept", "stepSafety", "stepFacilitator", "stepTransparency"]
                maxPages = listOfViews.count
                return
            }

            if (items != nil) {

                if let newUser = (items?.value(forKey: "newUser") as? NSArray){

                    //Below is where the error "EXC_BAD_INSTRUCTION"
                    for key in (newUser as! NSDictionary).allKeys
                    {
                        if (((newUser as! NSDictionary).value(forKey: key as! String) as? Bool)!)
                        {
                            listOfViews.append(key as! String)
                        }
                    }

                }

                if (listOfViews.count == 0)
                {
                    listOfViews = ["stepConcept", "stepSafety", "stepFacilitator", "stepTransparency"]
                }

                maxPages = listOfViews.count
            }
        }
    }

Are you responsible for sending the JSON? If yes why do you send multiple dictionaries with only one key in an array (rather than one dictionary)? — vadian
– vadian, Commented Jul 29, 2017 at 17:21
The code was already in place, I'm rewriting it to fit the new json data — SwiftyJD
– SwiftyJD, Commented Jul 29, 2017 at 17:27

David Pasztor · Accepted Answer · 2017-07-29 18:25:07Z

2

I have changed your code to use native Swift structs. Since you are not handling errors or doing anything when your optional unwrapping doesn't work, I have also changed the unwrapping to guard statements.

Other than the serious problems with Swift coding practices, your issue was that you were trying to iterate through an array of dictionaries as a simple dictionary.

func prepareArrayOfViews(userType: User){
    guard let welcomeJSON = welcomeJSON else {return}
    guard let items = welcomeJSON["items"] as? [[String:Any]] else {
        listOfViews = ["stepConcept", "stepSafety", "stepFacilitator", "stepTransparency"]
            maxPages = listOfViews.count
            return
    }
    for item in items {
        if let newUser = item["newUser"] as? [[String:Any]] {
            for embeddedDict in newUser {
                for (key, value) in embeddedDict { 
                    if let val = value as? Bool, val == true {
                        listOfViews.append(key)
                    }
                }
            }
        } else if let switcher = item["switcher"] as? [[String:Any]]{
            for embeddedDict in switcher {
                for (key, value) in embeddedDict { 
                    if let val = value as? Bool, val == true {
                        //do whatever you need to with the value
                    }
                }
            }
        }
    }
    if (listOfViews.count == 0){
         listOfViews = ["stepConcept", "stepSafety", "stepFacilitator", "stepTransparency"]
    }   
    maxPages = listOfViews.count
}

edited Jul 29, 2017 at 18:25

answered Jul 29, 2017 at 17:32

David Pasztor

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9 Comments

SwiftyJD Over a year ago

Thanks for your help but the code is giving an error on the line : for (key, value) in embeddedDict - Type '(key: String, value: Any)' does not conform to protocol 'Sequence'

David Pasztor Over a year ago

@SwiftyJD my bad, accidentally casted newUser to a Dictionary instead of an array of dictionaries. See my updated code, it should work now.

David Pasztor Over a year ago

Glad I could help. If you found my answer helpful, please accept it.

SwiftyJD Over a year ago

After further testing it looks like something might be wrong with the line: guard let items = welcomeJSON["items"] as? [String:Any] because Its goes right to the else statement even when the JSON is available

SwiftyJD Over a year ago

Ok, I'll let the API guys know, thanks for your help, saved my Saturday afternoon.

|

Vadim Kozak · Accepted Answer · 2017-07-29 17:31:16Z

1

Because

//here newUser is an NSArray

     if let newUser = (items?.value(forKey: "newUser") as? NSArray){

                        //here newUser forced to NSDictionary 
                        for key in (newUser as! NSDictionary).allKeys

try to change this part to

if let newUsers = (items?.value(forKey: "newUser") as? NSArray){

                for newUser in newUsers
                {
                    for key in (newUser as! NSDictionary).allKeys
                {
                    if (((newUser as! NSDictionary).value(forKey: key as! String) as? Bool)!)
                    {
                        listOfViews.append(key as! String)
                    }
                }
                }

            }

edited Jul 29, 2017 at 17:31

answered Jul 29, 2017 at 17:29

Vadim Kozak

4203 silver badges11 bronze badges

3 Comments

SwiftyJD Over a year ago

I see, I do need to get the items in the newUser array as a dictionary for the key valued pairs, am I missing something? -Nevermind I see you updated your answer.

SwiftyJD Over a year ago

I get a SIGABRT error on this line: for key in (newUser as! NSDictionary).allKeys

David Pasztor Over a year ago

@SwiftyJD see my answer, which uses native Swift structs and no unsafe unwrappings

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