This code works fine in Swift 2:
guard let userData = responseData["UserProfile"] as? [String : AnyObject] else { return }
var userProfileFieldsDict = [String: String]()
if let profileUsername = userData["Username"] as? NSString {
userProfileFieldsDict["username"] = String(profileUsername)
}
if let profileReputationpoints = userData["ReputationPoints"] as? NSNumber {
userProfileFieldsDict["reputation"] = String(profileReputationpoints)
}
But, in Swift 3 it throws an error on userProfileFieldsDict["reputation"] saying
init has been renamed to init(describing:)
My question is why does it trigger on that line and not on the userProfileFieldsDict["username"] assignment line, and how to go about fixing it? I'm assuming it's because I'm casting a NSNumber to a String, but I can't really understand why that matters.
NSNumber is a very generic class. It can be anything from a bool to a long to even a char. So the compiler is really not sure of the exact data type hence it's not able to call the right String constructor.
Instead use the String(describing: ) constructor as shown below
userProfileFieldsDict["reputation"] = String(describing: profileReputationpoints)
Here's more info about it.
You need to drop your use of Objective-C types. This was always a bad habit, and now the chickens have come home to roost. Don't cast to NSString and NSNumber. Cast to String and to the actual numeric type. Example:
if let profileUsername = userData["Username"] as? String {
userProfileFieldsDict["username"] = profileUsername
}
if let profileReputationpoints = userData["ReputationPoints"] as? Int { // or whatever
userProfileFieldsDict["reputation"] = String(profileReputationpoints)
}
Related
I am trying to read from a JSON String and draw a graph with its data:
{"y-axis-data":{"min":0.0,"max":1000,"Step":100.0},"x-labels":[1994,2000,2005],"y-values":[20,305,143]}
I wrote a function to create a dictionary from the string:
func jsonToDictionary(jsonString: String) -> [String: Any]? {
if let jsonData: Data = jsonString.data(using: String.Encoding.utf8) {
do {
return try (JSONSerialization.jsonObject(with: jsonData, options: []) as? [String: Any])!
} catch {
some bla bla
}
}
return nil
}
The return dictionary should count 3 elements inside when I pass my JSON string, and it does.
I can then change of some variables (Double) which are 0 until now and give them the values of min max and Step from the "y-axis-data" key of my dictionary, using {"min":0.0,"max":1000,"Step":100.0} as a dictionary it self. Works fine.
My trouble comes when trying to initialize other atributes:
self.my_view!.x-labels = (jsonToDictionary!["x-labels"]) as? NSMutableArray
my_view has already been initialized as UIViewCustomClass(frame: someFrame)
myview.x-labels is an NSMutableArray and it is initialized as nil. After executing that line of code it is still nill, of course myview.x-labels.count is nil. if I do it this way:
self.my_view!.x-labels = (jsonToDictionary!["x-labels"]) as! NSMutableArray
I get a warning :
Treating a forced downcast to NSMutableArray as optional will never produce nil.
It then crashes on runtime with this error:
Could not cast value of type '__NSArrayI' (0x110ed5448) to 'NSMutableArray' (0x110ed4598).
of course the exact same thing happens with "y-values"
What is the right way to do this?
It was because your json!["x-labels"] is implicitly treated as NSArray, so you somehow had to do a "double-force-cast"
// get the converted json
let j = jsonToDictionary(jsonString: dict)
// double cast
let m = (j!["x-labels"] as! NSArray).mutableCopy() as! NSMutableArray
Result:
I think, JSONSerialization class converts into Array, and then Swift cannot cast Array to NSMutableArray. You can do this (Swift4):
let array = (jsonToDictionary!["x-labels"]) as? [Int]
if array != nil {
self.my_view!.x-labels = NSMutableArray(array: array!)
}
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 {
...
I am using the following code to get data from an API:
typealias JSONdic = [String: AnyObject]
if let json = json as? JSONdic, history = json["history"] as? JSONdic, hour = history["hour"] as? String {
println(hour)
}
However, Xcode tells me that "json" is not a recognized identifier. I believe this can be solved with NSURLConnection, but I have no idea how to use that. Can anyone provide any examples of this protocol in use?
You're declaring a variable by setting it to itself, which doesn't make any sense. In order to use a variable on the right hand side of an assignment, it needs to have already been declared. So let's give json a value outside of the casting statements and it works fine.
typealias JSONdic = [String: AnyObject]
let json: AnyObject = ["greeting": "Hello"]
if let json = json as? JSONdic, history = json["history"] as? JSONdic, hour = history["hour"] as? String {
println(hour)
}
While exploring a structure read from a json file, I've got this message on the “if let” line which I'm stuck with:
'String' is not a subtype of '(String, AnyObject)'
The code is as follows:
if let descriptions: Array<Dictionary<String,AnyObject>> = fields["description"] as? Array {
let description = descriptions[0]
if let text:String = description["text"] as? String { // where the error occurs
poi.description = text
}
}
You have to unwrap what's read from the description dictionary:
if let text:String = description["text"]! as? String { // where the error occurs
...
}
But that's not safe, because if the key is not found in the dict, it throws a runtime exception. A safer way is:
if let text:String = (description["text"] as AnyObject?) as? String { // where the error occurs
...
}
However, I presume that you're using NSJSONSerialization to deserialize your json data, so a better way to do that is to stick with obj-c types rather than pure swift data types with generics:
if let descriptions = fields["description"] as? NSArray {
let description = descriptions[0] as NSDictionary
if let text = description["text"] as? String {
let x = text
}
}
More compact and much easier to read.
Use the new syntax and less of it.
Test declarations: Dictionary of Array of Dictionary
// let testFields: [String:[[String:Any]]]
or
// let testFields: [String:[[String:String]]]
let testFields = ["description":[["text":"value"]]]
if let descriptions = testFields["description"] {
let description = descriptions[0]
if let text = description["text"] as String? {
println("text: \(text)")
}
}
Output:
text: value
I want to parse a JSON to object, but I have no idea how to cast AnyObject to String or Int since I'm getting:
0x106bf1d07: leaq 0x33130(%rip), %rax ; "Swift dynamic cast failure"
When using for example:
self.id = reminderJSON["id"] as Int
I have ResponseParser class and inside of it (responseReminders is an Array of AnyObjects, from AFNetworking responseObject):
for reminder in responseReminders {
let newReminder = Reminder(reminderJSON: reminder)
...
}
Then in Reminder class I'm initialising it like this (reminder as AnyObject, but is Dictionary(String, AnyObject)):
var id: Int
var receiver: String
init(reminderJSON: AnyObject) {
self.id = reminderJSON["id"] as Int
self.receiver = reminderJSON["send_reminder_to"] as String
}
println(reminderJSON["id"]) result is: Optional(3065522)
How can I downcast AnyObject to String or Int in case like this?
//EDIT
After some tries I come with this solution:
if let id: AnyObject = reminderJSON["id"] {
self.id = Int(id as NSNumber)
}
for Int and
if let tempReceiver: AnyObject = reminderJSON["send_reminder_to"] {
self.id = "\(tempReceiver)"
}
for string
In Swift, String and Int are not objects. This is why you are getting the error message. You need to cast to NSString and NSNumber which are objects. Once you have these, they are assignable to variables of the type String and Int.
I recommend the following syntax:
if let id = reminderJSON["id"] as? NSNumber {
// If we get here, we know "id" exists in the dictionary, and we know that we
// got the type right.
self.id = id
}
if let receiver = reminderJSON["send_reminder_to"] as? NSString {
// If we get here, we know "send_reminder_to" exists in the dictionary, and we
// know we got the type right.
self.receiver = receiver
}
reminderJSON["id"] gives you an AnyObject?, so you cannot cast it to Int You have to unwrap it first.
Do
self.id = reminderJSON["id"]! as Int
if you're sure that id will be present in the JSON.
if id: AnyObject = reminderJSON["id"] {
self.id = id as Int
}
otherwise
Now you just need to import Foundation. Swift will convert value type(String,int) into object types(NSString,NSNumber).Since AnyObject works with all objects now compiler will not complaint.
This is actually pretty simple, the value can be extracted, casted, and unwrapped in one line: if let s = d["2"] as? String, as in:
var d:[String:AnyObject] = [String:AnyObject]()
d["s"] = NSString(string: "string")
if let s = d["s"] as? String {
println("Converted NSString to native Swift type")
}