I am fairly new to the Swift syntax and am receiving this error with my code "Cannot assign through subscript: subscript is get only"
This is from the line: friendDictionary[(friendUID as? String)!] = ["name": friendsData!["name"]]
Any advice on the correct way of doing it would be very helpful.
func getFriendsUIDs() {
if FBSDKAccessToken.currentAccessToken() == nil {
print("failed to start graph request")
return
}else{
}
if FBSDKAccessToken.currentAccessToken() != nil {
}
let parameters = ["fields": "name, id, picture"]
FBSDKGraphRequest(graphPath: "/me/friends", parameters: parameters).startWithCompletionHandler {
(NSURLConnection, result, requestError) in
let friendIds = result["id"] as? NSDictionary
let friendsData = friendIds!["data"] as? [NSDictionary]
var ref: FIRDatabaseReference!
ref = FIRDatabase.database().reference()
ref.child("users").child((FIRAuth.auth()?.currentUser?.uid)!).child("friendUIDs").observeEventType(.Value, withBlock: { (snapshot) in
self.FriendUIDs = NSArray()
self.FriendUIDs = (snapshot.value as? NSArray)!
print(self.FriendUIDs)
var friendDictionary = NSDictionary()
for friendUID in self.FriendUIDs {
friendDictionary[(friendUID as? String)!] = ["name": friendsData!["name"]]
}
self.fetchFriendFeed(friendDictionary)
}) { (error) in
print(error.localizedDescription)
}
}
}
func fetchFriendFeed(friendDictionary: NSDictionary) {
var ref: FIRDatabaseReference!
ref = FIRDatabase.database().reference()
for friendUID in FriendUIDs {
ref.child("users").child(friendUID as! String).child("Agenda").observeEventType(.ChildAdded, withBlock: { (snapshot) in
print(snapshot)
if let dictionary = snapshot.value as? [String: AnyObject] {
let friendPost = FriendPost()
friendPost.picture = friendDictionary[friendUID as! String]? ["picture"] as? String
friendPost.activity = dictionary["activity"] as? String
friendPost.date = dictionary["date"] as? String
friendPost.time = dictionary["time"] as? String
friendPost.friendname = friendDictionary[friendUID as! String]? ["name"] as? String
self.friendPosts.append(friendPost)
dispatch_async(dispatch_get_main_queue(), {
self.collectionView?.reloadData()
Nothing to do with Swift. You've elected to use Objective-C, in effect, by making friendDictionary an NSDictionary. NSDictionary is immutable; you can't assign into it or alter it in any way. That is simply a fact about Objective-C. The Swift var declaration makes no difference to this fact.
A better choice, since you are writing in Swift, would be to use a Swift dictionary, which is [AnyHashable:Any]() (in Swift 3). This will interchange with NSDictionary when you are talking to Objective-C, but it will give you a mutable dictionary because you (rightly) declared it with var.
Have you tried using NSMutableDictionary? That solved the issue for me.
For those who get stuck here, another reason for this happens when you try to assign something that does not conform the actual dictionary, in my example i was doing something like this:
var dict = [Date : UUID]()
let randomUUID = UUID()
dict[randomUUID] = Date.now
whereas I meant to write UUID : Date but I was sleepy so i made a mistake, and Swift gave me a misleading error saying subscript is get-only. So this error also appears with type mismatch for Swift 5.7.
Related
I'm a newb to Swift programming, but experience in other languages.
I am having problem accessing items within NSDictionary to build out view elements. This is coming back from a Firebase instance.
Can someone take a look at the code and the output and lead me in the right direction to access these object properties?
ref.observe(.value, with: { (snapshot) in
for child in snapshot.children { //even though there is only 1 child
let snap = child as! DataSnapshot
let dict = snap.value as? NSDictionary
for (joke, item) in dict ?? [:] {
print(joke)
print(item)
}
}
})
This is the output from the print() methods.
joke2
{
PostUser = "Bobby D";
Punchline = "His money went to the movies.";
Rating = 1;
Setup = "Why did the dad go hungry?";
}
joke
{
PostUser = "Billy G";
Punchline = "Because he couldn't moo to a job.";
Rating = 3;
Setup = "Why did the cow go to school?";
}
Can someone tell me how to create items from these objects? Something like:
var posterName = joke.PostUser
When I try this, I get the error Value of type 'Any' has no member 'PostUser'. I've tried to access these DB object properties in multiple different ways described on SO and can't get any further.
I would recommend you to convert the output into objects like this:
struct Item {
var postUser: String?
var punchline: String?
var rating: Int?
var setup: String?
init(fromDict dict: [String: AnyObject] ) {
self.postUser = dict["PostUser"] as? String
self.punchline = dict["Punchline"] as? String
self.rating = dict["Rating"] as? Int
self.setup = dict["Setup"] as? String
}
}
And use it like this:
ref.observe(.value, with: { (snapshot) in
for child in snapshot.children {
let snap = child as! DataSnapshot
guard let dict = snap.value as? [String: AnyObject] else { continue }
let myItem = Item(fromDict: dict)
print(myItem)
}
})
But you could also access items in your dictionary directly like this:
let posterName = joke["PostUser"] as? String
I have this code
let jsonData = try JSONSerialization.jsonObject(with: data, options: []) as! [Any?]
if var first = jsonData[0] as! String?{
if(first=="Error"){
DispatchQueue.main.async(execute: {
self.postNotFoundLabel.isHidden = false
});
}else if(first=="Empty"){
print("Empty")
}
}
What i want to do is to cast jsonData[0] to String if it's possible and if it's not then move on.But instead when it's not possible application stops and gives me an error
Could not cast value of type '__NSDictionaryI' (0x1092054d8) to 'NSString' (0x108644508).
How can i cast only when it's possible?
You are trying to force-cast to an optional String. That's not what you want.
Change:
if var first = jsonData[0] as! String? {
to:
if var first = jsonData[0] as? String {
This tries to cast to String. If jsonData[0] isn't actually a String, you get nil and the if var fails.
And you probably want if let, not if var since you don't seem to be making any change to first.
First of all JSON objects will never return optional values so [Any?] is nonsense.
Second of all the error message says the type cast to string is inappropriate because the type of the result is actually a dictionary.
Solution: Check the type for both String and Dictionary
if let jsonData = try JSONSerialization.jsonObject(with: data) as? [Any],
let first = jsonData.first {
if let firstIsDictionary = first as? [String:Any] {
// handle case dictionary
} else if let firstIsString = first as? String {
// handle case string
}
}
PS: A type cast forced unwrap optional to optional (as! String?) is nonsense, too.
Here's the Swifty way to do what you're doing :)
guard let jsonData = try JSONSerialization.jsonObject(with: data, options: []) as? [Any?], let first = jsonData[0] as? String else {
DispatchQueue.main.async(execute: {
self.postNotFoundLabel.isHidden = false
});
return
}
if(first == "Empty") {
print(first)
}
Don't use as! if you are not sure that casting will succeed. The exclamation mark after the as keyword forces the casting, which throws an error if the casting does not succeed.
Use as? instead, which returns an optional variable of the type you were trying to casting to. If the casting fails, instead of throwing an error, it just returns nil.
let jsonData = try JSONSerialization.jsonObject(with: data) as? [Any]
if var first = jsonData.first as? String{
if(first=="Error"){
DispatchQueue.main.async(execute: {
self.postNotFoundLabel.isHidden = false
});
}else if(first=="Empty"){
print("Empty")
}
}
I am trying to parse the emergency data in into emergency struct but it never statifies the condition and get into else case.Here is my code and structure.Some thing i have written woring in first line.
if let emergencyDict = snapshotValue["emergency"] as? [String:[String:Any]]{
for (emerId, emerData) in emergencyDict {
let emer = Emergency.init(emergency: emerData as NSDictionary)
emergency.append(emer)
}
}
else{
let emer = Emergency.init(emerg: "" as AnyObject)
emergency.append(emer)
}
struct Emergency{
var emer_id: String
var emer_name: String
var emer_phoneNo: String
init(emergency: NSDictionary) {
if emergency.object(forKey: "id") != nil {
emer_id = emergency.object(forKey: "id") as! String
}
else{
emer_id = ""
}
}
}
The problem you are having emergency as Array with type [Any] and if you remove the first object then you get Array of type [[String:Any]]. So try like this way.
if let array = snapshotValue["emergency"] as? [Any],
let emergencyArrar = Array(array.dropFirst()) as? [[String:Any]] {
print(emergencyArray)
for emergency in emergencyArray {
print(emergency)
}
}
You have written wrong in this line:
if let emergencyDict = snapshotValue["emergency"] as? [String:[String:Any]]{
It should be:
if let emergencyDict = snapshotValue["emergency"] as? [[String:Any]]{
This question should belong to query from firebase database.
// you have to get the children in emergency,
// then get the value(dictionary) of each child
ref.child("emergency").observeSingleEvent(of: .value, with: { (snapshot) in
let value = snapshot.value as? NSDictionary
let keys = value?.allKeys // [1, 2, 3 ....]
for key in keys {
ref.child("emergency").child(key)..observeSingleEvent(of: .value, with: { (snapshot) in
let value = snapshot.value as? NSDictionary
// Here is your dictionary
}
}
}) { (error) in
print(error.localizedDescription)
}
I am on point where I gotta compare non optional value with nil. But I can't do it because Xcode says:
Comparing non-optional value of type 'Int' to nil always returns false
So I created Struct and then made variable: var products: [Product] = []
How I am able to compare it with nil?:
if products[indexPath.row].snusPortions == nil
{
cell.snusPortionsAmountLabel.text = "N/A"
}else
{
cell.snusPortionsAmountLabel.text = String(products[indexPath.row].snusPortions)
}
I've assigned values to them like this:
let ref = FIRDatabase.database().reference().child("Snuses").queryOrdered(byChild: "Brand").queryEqual(toValue: brandName)
ref.observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.exists(){
let enumerator = snapshot.children
while let thisProduct = enumerator.nextObject() as? FIRDataSnapshot
{
print(thisProduct.value) // So I may see what the data is like and know how to extract it
// Chances are you'd have to create a dictionary
let thisProductDict = thisProduct.value as! [String:AnyObject]
let productName = thisProductDict["Products"] as! String
let snusPortions = thisProductDict["PortionsCan"] as? Int
let productObject = Product(snusProductTitle: productName, snusNicotine: snusNicotine, snusPortions: snusPortions!, snusFlavor: snusFlavor, snusWeight: snusWeight!, snusShippingWeight: snusShippingWeight, snusProductImageURL: productURL)
self.products.append(productObject)
print(self.products)
}
self.tableView.reloadData()
}
})
This is Product struct:
struct Product {
var snusProductTitle: String
init()
{
snusProductTitle = ""
}
init(snusProductTitle: String){
self.snusProductTitle = snusProductTitle
}
}
While testing it says snusPortions is nil but I said to make it "N/A" if it is nil, why?
It sounds like you are confusing yourself between the local variable snusPortions and the Product property snusPortions.
In your Product definition, the property snusPortions is an Int. It can never be nil. Hence, in this code:
if products[indexPath.row].snusPortions == nil
... this Product's snusPortions will never be nil, and we will never set the text to "N/A".
Now let's look at your other code:
let snusPortions = thisProductDict["PortionsCan"] as? Int
This is a completely different snusPortions. It can be nil, namely, if thisProductDict lacks a "PortionsCan" key or if its value is not castable to Int.
I have a lot of issues in my code with this error. Hopefully if someone can help me here than I can figure out the rest of the problems. I have updated to xcode 7.3 and running swift 2.2.
I have read that the compiler has been "more restrictive", and I have to tell it what the "intermediary" objects are. This is causing me some confusion and would love further explanation.
func getMessage(dictionary:NSDictionary)->String{
var message = String()
if let dict = dictionary["aps"] {
if let message:String = dict["alert"] as? String {
return message
}
else{
message = ""
}
}
return message
}
Another example:
for object in objects {
let getDriver = object.objectForKey("driver")
if let picture = getDriver!["thumbnailImage"] as? PFFile {
self.profilePictures.append(picture)
}
self.requestsArray.append(object.objectId as String!)
}
The type of a dictionary value is always AnyObject. Cast the type to something more specific for example
if let dict = dictionary["aps"] as? [String:AnyObject] {
then the compiler knows that key subscripting is valid and possible
The second example is similar: object is a dictionary and the compiler needs to know that the value for key driver is also a dictionary
if let getDriver = object.objectForKey("driver") as? [String:AnyObject] {
if let picture = getDriver["thumbnailImage"] as? PFFile {
...