I have a Dictionary that has a User object, and that User object is a dictionary that has a key "Name".
In Swift, i need to access the value for "Name".
So I did the following:
let user = question[kUserOwner] as! PFUser
let userName = user[kName] as! String
userButton.setTitle(userName, forState:UIControlState.Normal)
1) Is there really no easier/shorter way to do this?
In Objective C:
[_userButton setTitle:[[question objectForKey:kUserOwner] objectForKey:kName] forState:UIControlStateNormal];
I do realize that it is not Type safe but I can live with that, as long as I know what I am doing.
2) Is there any way i can avoid casting?
When you subscript, you get an Optional. And you cannot subscript an Optional. Therefore, while you can perhaps avoid casting, you cannot avoid unwrapping:
let dinner = ["name":"Matt"]
let douter = ["owner":dinner]
let name = douter["owner"]!["name"]
But that only works because Swift knows very specifically what douter is. It would be better, therefore, to do this in stages, as Swift expects you to do, e.g. with a nested series of if let bindings:
let dinner : AnyObject = ["name":"Matt"] as AnyObject
let douter : AnyObject = ["owner":dinner] as AnyObject
if let owner = douter["owner"] as? [NSObject:AnyObject],
let name = dinner["name"] as? String {
// do something with name
}
Related
I set up breakpoints all along my function, everything is running fine, but when it comes to the print part, it always skips over it.
func testForGettingAllValues(){
let uid = user2?.id
let ref = FIRDatabase.database().reference().child("user-reviews").child(uid!)
ref.observe(.childAdded, with: {(firstSnapshot) in
let reviewId = firstSnapshot.key
let messageReference = FIRDatabase.database().reference().child("reviews").child(reviewId)
messageReference.queryOrdered(byChild: "ratingNumber").observeSingleEvent(of: .value, with: {(reviewSnapshot) in
if reviewSnapshot.exists(){
if let values = reviewSnapshot.value as? [String:AnyObject]{
for reviews in values {
if let ratingNumber = reviews.value["ratingNumber"] as? String{
print("This is the ratingNumber list", ratingNumber)
}
}
}
}
})
})
}
}
In you nestedness, the following holds:
if binding to values is successful, it is of type [String:AnyObject]
each reviews instances is a named tuple of type (key: String, value: AnyObject)
when you try to bind to ratingNumber, you access the value property of reviews, and act as if this value property is a dictionary itself. However, it is not, it is of type AnyObject.
Most likely, in the third bullet above, lies the logical error, which in turn cause the innermost optional binding to fail. The compiler cannot know whether or not the AnyObject instance accessible by reviews.value is in fact wrapping a dictionary (an NSDictionary, perhaps?). You could attempt to first attempt a type conversion of it to the dictionary type you believe it to be, and thereafter attempting to access the "ratingNumber" key of the converted value.
Possibly (without the chance to test this out myself, due to your lack of a reproducable example ...):
if let ratingNumber = (reviews.value as? [String: String])?["ratingNumber"]
This is what I am trying to do with the dictionary:
if let deliveries = dictionary["deliveries"] as? NSDictionary {
var castedDeliveries = [Double: Double]()
for delivery in deliveries {
if let value = delivery.value as? Double {
castedDeliveries[Double(delivery.key as! NSNumber)] = value //Could not cast value of type 'NSTaggedPointerString' (0x1a1e3af20) to 'NSNumber' (0x1a1e458b0).
}
}
settings!.deliveries = castedDeliveries
}
And this is what I try to cast, as a part of JSON response from server:
deliveries = {
2 = 0;
5 = "2.59";
7 = "3.59";
};
It doesnt work, because there is an error at commented line:
Could not cast value of type 'NSTaggedPointerString' (0x1a1e3af20) to 'NSNumber' (0x1a1e458b0).
You are trying to cast dictionary directly but instead you need to cast each key - value pair. If you want generic solution to this problem take a look at SwiftyJSON library which address JSON parsing problem for you.
Casting doens't mean data transformation from a type to another.
Your dictionary seems to be composed by Integer keys and String values.
If you want to transform in something else you ca use the map function.
let converted = deliveries.map{[Double($0) : Double($1)]}
But pay attention.
Here we are saying, iterate over the dictionary (in the $0 there is the dictionary key in the $1 there is the value) and create a new dictionary that has as a key a Double initialized at the key value and as a new value a Double initialized as the old dictionary value. The last conversion can fail, so the returned data is an optional.
As I noted in the comments, this isn't casting. You want a data conversion. You need to do that explicitly, especially in this case since it might fail.
Looking at the error, I think you really have a dictionary of [String:String] here (in NSDictionary form). That suggests the JSON is badly encoded, but such is life. Assuming that dictionary looks something like this:
let dictionary: NSDictionary = ["deliveries": ["2":"0", "5": "2.59", "7": "3.59"]]
You would convert it to [Double:Double] like this:
if let jsonDeliveries = dictionary["deliveries"] as? [String:String] {
var deliveries: [Double: Double] = [:]
for (key, value) in jsonDeliveries {
if let keyDouble = Double(key),
valueDouble = Double(value) {
deliveries[keyDouble] = valueDouble
}
}
// Use deliveries
}
This silently ignores any values that can't be converted to Double. If you would rather generate errors, use a guard let rather than an if let.
I am trying since a whole day migrating my localStorage data to realm.io...
Now the only issue I am facing is that I can get the object property using
object.valueforKey("key")
but not using the simpler one
object.key
Here you have a peace of my code
let realm = try! Realm()
let predicate = NSPredicate(format: "groupID = %#", group.valueForKey("groupID") as! String )
let current = realm.objects(apiGroup).filter(predicate)
let currentGroup = current[0]
print(currentGroup.valueForKey("token") as! String)
print(currentGroup.token)
When I execute that this is been printed on the console.
56abbf408cfea7941a8b30b7
fatal error: unexpectedly found nil while unwrapping an Optional value
Can you please tell me if this is the normal behaviour or if I can do something to get the
"object.key"
notation??
Thanks in advance
Thanks all for your views. I ended up creating a custom object with a custom init and passing realm object to it...
Then I looped the realm object to assign the same object properties to the custom one... example
class Images:Object{
var picid:String = ""
var path:String = ""
var timeStamp:NSDate!
override class func primaryKey() -> String{
return "picid"
}
}
class realmImages{
var picid:String!
var path:String!
var timeStamp:NSDate!
init(object:Images){
picid = object.valueForKey("picid") as! String
path = object.valueForKey("path") as! String
timeStamp = object.valueForKey("timeStamp") as! NSDate
}
}
Hang on! I think I didn't actually understand the question properly!
If the .token property is actually a member of your class, that should absolutely work. Just to confirm, are you defining your members of your Realm model subclass properly, according to the documentation?
class APIGroup: Object {
dynamic var token = ""
}
If so, and you're STILL having trouble, it may be possible that Swift wasn't able to infer that the type of the object returned from the filter wasn't your APIGroup object (Which would explain why valueForKey still works).
If that's the case, stating the type should help:
let currentGroup = current[0] as APIGroup
Let me know if that helped!
I am currently trying to get a value called "loot" out of the current user. I need the value as a String, but Swift is being stubborn and says it "cannot convert Anyobject to String". The Parse documentation for iOS says to use something like:
let score = gameScore["score"] as String
and so, I try this :
let lootAmount = user["loot"] as String
BTW 'user' is referring to the current user. When I try that, it gives error saying it's not convertible. I tried placing '!'s and '?'s wherever Xcode suggested, but it just crashed the app with no error.
So, how do I get the user value called "loot" as a String?
Loot is an NSNumber not an NSString or String.
You could convert it to a String like this:
if let loot = user["loot"] as? NSNumber {
let lootString = "\(loot)"
}
If you're not sure of an object's type, you can ask it using dynamicType:
print(user["loot"]!.dynamicType)
//prints `__NSCFNumber.Type`
You may need to downcast AnyObject. Try this: let lootAmount = user["loot"] as? String or unwrap your optional user if you haven't done so:
let currentUser = PFUser.currentUser()
if let user = currentUser {
let lootAmount = user["loot"] as String
}
I am doing what I believe to be a very simple task. I'm trying to get a value out of a dictionary if the key exists. I am doing this for a couple keys in the dictionary and then creating an object if they all exist (basically decoding a JSON object). I am new to the language but this seems to me like it should work, yet doesn't:
class func fromDict(d: [String : AnyObject]!) -> Todo? {
let title = d["title"]? as? String
// etc...
}
It gives me the error: Operand of postfix ? should have optional type; type is (String, AnyObject)
HOWEVER, if I do this, it works:
class func fromDict(d: [String : AnyObject]!) -> Todo? {
let maybeTitle = d["title"]?
let title = maybeTitle as? String
// etc...
}
It appears to be basic substitution but I may be missing some nuance of the language. Could anyone shed some light on this?
The recommended pattern is
if let maybeTitle = d["title"] as? String {
// do something with maybeTitle
}
else {
// abort object creation
}
It is possibly really a question of nuance. The form array[subscript]? is ambiguous because it could mean that the whole dictionary (<String:AnyObject>) is optional while you probably mean the result (String). In the above pattern, you leverage the fact that Dictionary is designed to assume that accessing some key results in an optional type.
After experimenting, and noticing that the ? after as is just as ambiguous, more, here is my solution:
var dictionary = ["one":"1", "two":"2"]
// or var dictionary = ["one":1, "two":2]
var message = ""
if let three = dictionary["three"] as Any? {
message = "\(three)"
}
else {
message = "No three available."
}
message // "No three available."
This would work with all non-object Swift objects, including Swift Strings, numbers etc. Thanks to Viktor for reminding me that String is not an object in Swift. +
If you know the type of the values you can substitute Any? with the appropriate optional type, like String?
There are a few of things going on here.
1) The ? in d["title"]? is not correct usage. If you're trying to unwrap d["title"] then use a ! but be careful because this will crash if title is not a valid key in your dictionary. (The ? is used for optional chaining like if you were trying to call a method on an optional variable or access a property. In that case, the access would just do nothing if the optional were nil). It doesn't appear that you're trying to unwrap d["title"] so leave off the ?. A dictionary access always returns an optional value because the key might not exist.
2) If you were to fix that:
let maybeTitle = d["title"] as? String
The error message changes to: error: '(String, AnyObject)' is not convertible to 'String'
The problem here is that a String is not an object. You need to cast to NSString.
let maybeTitle = d["title"] as? NSString
This will result in maybeTitle being an NSString?. If d["title"] doesn't exist or if the type is really NSNumber instead of NSString, then the optional will have a value of nil but the app won't crash.
3) Your statement:
let title = maybeTitle as? String
does not unwrap the optional variable as you would like. The correct form is:
if let title = maybeTitle as? String {
// title is unwrapped and now has type String
}
So putting that all together:
if let title = d["title"] as? NSString {
// If we get here we know "title" is a valid key in the dictionary, and
// we got the type right. title has now been unwrapped and is ready to use
}
title will have the type NSString which is what is stored in the dictionary since it holds objects. You can do most everything with NSString that you can do with String, but if you need title to be a String you can do this:
if var title:String = d["title"] as? NSString {
title += " by Poe"
}
and if your dictionary has NSNumbers as well:
if var age:Int = d["age"] as? NSNumber {
age += 1
}