I have some data I stored into a dictionary which is defined as:
let data = Dictionary<String, AnyObject>()
In this dictionary the value is always a string, but the value can be an array or integer or string. But when I try to access an item in a array in this dictionary, like:
let item = data["key"][0]
It gives me this error:
Cannot subscript value of type "AnyObject"
How should I access that item?
You need to tell the compiler that you're expecting an array:
if let array = data["key"] as? [Int] {
let item = array[0]
}
Without that, the compiler only knows that there MAY be an AnyObject in data["key"] (it might also be nil).
Related
I try to convert my code to swift 3 an I have spent hours on the following error:
Type 'Any' has no subscript members
Here's was my original code:
let data: AnyObject = user.object(forKey: "profilePicture")![0]
I looked at the answers here but I'm still stuck. (I do programming as a hobby, I'm not a pro :/)
I've try that:
let object = object.object(forKey: "profilePicture") as? NSDictionary
let data: AnyObject = object![0] as AnyObject
But now I get this error:
Variable used within its own initial value
Second issue: Use always a different variable name as the method name, basically use more descriptive names than object anyway.
First issue: Tell the compiler the type of the value for profilePicture, apparently an array.
if let profilePictures = user["profilePicture"] as? [[String:Any]], !profilePictures.isEmpty {
let data = profilePictures[0]
}
However, the array might contain Data objects, if so use
if let profilePictures = user["profilePicture"] as? [Data], !profilePictures.isEmpty {
let data = profilePictures[0]
}
Or – what the key implies – the value for profilePicture is a single object, who knows (but you ...)
And finally, as always, don't use NSArray / NSDictionary in Swift.
let employerName = snapshot.value! ["employerName"] as! String
let employerImage = snapshot.value! ["employerImage"] as! String
let uid = snapshot.value! ["uid"] as! String
I reviewed previous posts but cannot seem to find a way to solve this problem. All three lines of code give the "type 'Any' has no subscript members" error. Fairly new to this so any help is appreciated.
snapshot.value has a type of Any. A subscript is a special kind of function that uses the syntax of enclosing a value in braces. This subscript function is implemented by Dictionary.
So what is happening here is that YOU as the developer know that snapshot.value is a Dictionary, but the compiler doesn't. It won't let you call the subscript function because you are trying to call it on a value of type Any and Any does not implement subscript. In order to do this, you have to tell the compiler that your snapshot.value is actually a Dictionary. Further more Dictionary lets you use the subscript function with values of whatever type the Dictionary's keys are. So you need to tell it you have a Dictionary with keys as String(AKA [String: Any]). Going even further than that, in your case, you seem to know that all of the values in your Dictionary are String as well, so instead of casting each value after you subscript it to String using as! String, if you just tell it that your Dictionary has keys and values that are both String types (AKA [String: String]), then you will be able to subscript to access the values and the compiler will know the values are String also!
guard let snapshotDict = snapshot.value as? [String: String] else {
// Do something to handle the error
// if your snapshot.value isn't the type you thought it was going to be.
}
let employerName = snapshotDict["employerName"]
let employerImage = snapshotDict["employerImage"]
let uid = snapshotDict["fid"]
And there you have it!
Since you want to treat snapshot.value as an unwrapped dictionary, try casting to one and, if it succeeds, use that dictionary.
Consider something like:
func findElements(candidate: Any) {
if let dict: [String : String] = candidate as? Dictionary {
print(dict["employerName"])
print(dict["employerImage"])
print(dict["uid"])
}
}
// Fake call
let snapshotValue = ["employerName" : "name", "employerImage" : "image", "uid" : "345"]
findElements(snapshotValue)
class X {
static let global: [String:String] = [
"x":"x data",
"y":"y data",
"z":"z data"
]
func test(){
let type = "x"
var data:String = X.global[type]!
}
}
I'm getting the error: Value of optional type 'String?' not unwrapped.
Why do I need to use ! after X.global[type]? I'm not using any optional in my dictionary?
Edited:
Even if X.global[type] may not exist for the type, force unwrapping will still crash on runtime. A better approach may be:
if let valExist = X.global[type] {
}
but Xcode is giving me the wrong idea by hinting about optional type.
Dictionary accessor returns optional of its value type because it does not "know" run-time whether certain key is there in the dictionary or not. If it's present, then the associated value is returned, but if it's not then you get nil.
From the documentation:
You can also use subscript syntax to retrieve a value from the dictionary for a particular key. Because it is possible to request a key for which no value exists, a dictionary’s subscript returns an optional value of the dictionary’s value type. If the dictionary contains a value for the requested key, the subscript returns an optional value containing the existing value for that key. Otherwise, the subscript returns nil...
In order to handle the situation properly you need to unwrap the returned optional.
There are several ways:
Option 1:
func test(){
let type = "x"
if var data = X.global[type] {
// Do something with data
}
}
Option 2:
func test(){
let type = "x"
guard var data = X.global[type] else {
// Handle missing value for "type", then either "return" or "break"
}
// Do something with data
}
Option 3:
func test(){
let type = "x"
var data = X.global[type] ?? "Default value for missing keys"
}
If we look at the Dictionary implementation, subscript is returning a ValueType as optional because it doesn't know if the key is exists or not:
//Reading a key that is not present in `self` yields `nil`.
//Writing `nil` as the value for a given key erases that key from `self`.
subscript (key: KeyType) -> ValueType?
So when we try to get a value from our Dictionary we get it as an optional from the subscript; that is we have to unwrap the optional to get the underlying object. As mentioned in earlier answers, option2 is preferred.
guard var data = X.global[type] else {
//key = 'type' doesn't exists
}
//key exists so do something with 'data'
I am trying to create a table view to show the content of a dictionary called tableText<String, String>. But in the cellForRowAtInSection method, when I do something like
let obj = tableText[indexPath.row]
It gives me a error saying that
cannot subscript a value of type 'Dictionary<String, String> with an index of Int.
I also tried things like
let obj = tableText[indexPath.row] as? NSDictionary
but the error is still there.
Could you help me with this please?
If you just want the values, you can get an array of values from the dictionary and used the indexPath.row on that array.
if let text = tableText.values[indexPath.row] as? String {
cell.textLabel.text = text
}
Obviously if you need them to be sorted you would have to sort them as dictionary is not sorted based on keys.
If you wanted them sorted alphabetically, you could do this
let sortedText = tableText.values.sorted { $0.localizedCaseInsensitiveCompare($1) == NSComparisonResult.OrderedAscending }
And use this sortedText array as your datasource
I have NSDictionary, I know it only has one key and one value, how can I directly get the first value from it?
thanks,
If you have a Swift Dictionary and you know you have exactly 1 key/value pair you can do this:
var dict = ["aaa":"bbb"]
let v = dict.values.first!
If you have more than 1 key/value pair then there is no "first" value since dictionaries are unordered. If you have no key/value pairs this will crash.
If you have an NSDictionary, you can use allValues.first!, but you'll have to cast the result because the value will be an AnyObject:
var dict:NSDictionary = ["aaa":"bbb"]
let v = dict.allValues.first! as! String
or:
let v = dict.allValues[0] as! String
Cast to a Swift Dictionary if it isn't one already. Then use the values property, cast to an Array, and get index 0.
let v = Array(myDictionary.values)[0]