I have a struct that looks like:
struct nameStruct {
let name: String
let index: Int
}
I have an NSMutableArray that contains about 50 objects of this struct
Right now, I fill the contents of my namesDict with
let namesDict:[String: Any] = ["names" : namesArray]
However, because I only need the index object for sorting, I'd like to only add the name attribute to the dictionary, something like this:
let namesDict:[String: Any] = ["names" : namesArray.name]
or, because of swift's nature:
let namesDict:[String: Any] = ["names" : (namesArray as! [nameStruct]).name]
(focus on the .name part which obviously doesn't work in Swift)
Right now, my best guess would be to create a new array in a loop, only adding the name of the contents of my namesArray - but if there was a way to do this in one line without another array "in between", this would be really nice.
You can use map.
let namesDict: [String: Any] = ["names": namesArray.map({ ($0 as! nameStruct).name })]
Related
I have declared a dictionary in Swift as so: var dict = [String: [String: [String]]]().
What I am trying to do now is to write to the nested dictionary. I have used both codes below, however, none of them work as the initial key does not exist:
dict["Test"]?["One"] = ["Failed"]
dict["Test"]!["One"] = ["Failed"]
What I am trying to do is to create a key for ["One"], much like how you can create a key for a normal dictionary using dict[key].
You need to instantiate every inner dictionary.
var dict = [String : [String : [String]]]()
dict["Test"] = [String : [String]]()
dict["Test"]?["One"] = ["Worked"]
print(dict)
Make sure to avoid force unwrapping.
dict is empty. There is no value for the "Test" key.
One option is to provide a default:
dict["Test", default: [:]]["One"] = ["A", "B"]
You can take this one step further:
dict["Test2", default: [:]]["Two", default: []].append("Hello")
That last line will work for any combination of the keys "Test2" and "Two" existing or not before that is used.
I would like to know how I can make a key of a dictionary have multiple values according to the data that comes to it.
Attached basic example:
var temp = [String: String] ()
temp ["dinningRoom"] = "Table"
temp ["dinningRoom"] = "Chair"
In this case, I always return "Chair", the last one I add, and I need to return all the items that I am adding on the same key.
In this case, the "dinningRoom" key should have two items that are "Table" and "Chair".
You can use Swift Tuples for such scenarios.
//Define you tuple with some name and attribute type
typealias MutipleValue = (firstObject: String, secondObject: String)
var dictionary = [String: MutipleValue]()
dictionary["diningRoom"] = MutipleValue(firstObject: "Chair", secondObject: "Table")
var value = dictionary["diningRoom"]
value?.firstObject
You can declare a dictionary whose value is an array and this can contain the data you want, for example:
var temp = [String: [String]]()
temp["dinningRoom"] = ["Table", "Chair", "Bottle"]
If you want to add a new element you can do it this way:
if temp["dinningRoom"] != nil {
temp["dinningRoom"]!.append("Flower")
} else {
temp["dinningRoom"] = ["Flower"]
}
Now temp["dinningRoom"] contains ["Table", "Chair", "Bottle", "Flower"]
Use Dictionary like this:
var temp = [String: Any]()
temp["dinningRoom"] = ["Table", "Chair"]
If you want to fetch all the elements from dinningRoom. You can use this:
let dinningRoomArray = temp["dinningRoom"] as? [String]
for room in dinningRoomArray{
print(room)
}
It is not compiled code but I mean to say that we can use Any as value instead of String or array of String. When you cast it from Any to [String]
using as? the app can handle the nil value.
I'm trying to look for items equal or less than zero in my query like so.....
for zeroItems in snapshot.value as! NSDictionary where zeroItems.value["Value"] as! Int <= 0
I'm getting an Expected type error. Please explain and show me how to correct.
You may want to consider applying a filter to simplify the logic to only include elements less than zero. I've created a working example in the IBM Swift Sandbox.
import Foundation
// Construct the data structure with demo data
struct Snapshot {
let value: NSDictionary
}
let dict: NSDictionary = [ "a" : -1, "b" : 0, "c" : 1]
let snapshot = Snapshot(value: dict)
//Apply a filter
let zeroItems = snapshot.value.filter{Int($0.1 as! NSNumber) <= 0}
//View the result
print(zeroItems)
Almost certainly you've overused Any if you have to use this many as! casts in a single line. Create a custom struct for this type and convert the data to that. If you're passing around NSDictionary and using as! very much, you're fighting the system.
That said, to make this work you probably just need more parentheses. Something like:
for zeroItems in (snapshot.value as! NSDictionary) where (zeroItems.value["Value"] as! Int) <= 0
But this is horrible Swift, so avoid this if possible.
You interpreting snapshot.value as Dictionary, so zeroItems is a tuple of key and value.
As I understand you having array of dictionaries, and you want to filter them by "Value" key, right?
If so then you may use following code:
// dictionary with Value key, and Int value
let dict: [String: Any] = ["Value":-1]
// array of dictionaries
let value: [[String: Any]] = [dict, <**add here as many as you want**>]
// get only array of integeres
let onlyIntegers = value.flatMap { $0["Value"] as? Int }.filter {$0 <= 0 }
print(onlyIntegers)
// get array of dictionaries which passes <=0 check
let onlyLessOrEqualTo0 = value.filter { dict in
if let value = dict["Value"] as? Int {
return value <= 0
}
return false
}
print(onlyLessOrEqualTo0)
First of all, adding some parentheses will help in seeing where the problem is:
for zeroItems in myDict as! NSDictionary where (zeroItems.value["Value"] as! Int) <= 0
Now, we get "Type 'Any' has no subscript members". So the problem is that you haven't told Swift what the type is of zeroItems's value, which I think is a dictionary of , judging from your code:
This compiles for me:
for zeroItems in myDict as! Dictionary<String, Dictionary<String, Int>> where zeroItems.value["Value"]! <= 0
However, this is not pretty. You could probably get more readable code using filter as was suggested in another answer.
It's not entirely that I can't solve this, but there are proper and improper ways and I don't want to use a flawed method. I have this snapshot from firebase, and I declare it as NSDictionary as so:
let commentDict = commentsDictionary.value as? NSDictionary
When I print commentDict it looks like this:
commentText = Fififgkffy;
postedBy = USXhV0QYkpbSzAmXgfeteXHuoqg2;
commentText = Fhzifigh;
postedBy = USXhV0QYkpbSzAmXgfeteXHuoqg2;
CommentDict will always look like this. It will always have 2 items. I want to know the proper way to grab the items and assign them to variables. One way I have used before, but just on one item is by putting this in a for loop:
if name as! String == "postedBy" {
Then I get the value for the "postedBy" dictionary item. When having 2 items though, should I make a little array for commentText and postedBY, and have 2 arrays with 2 items each? Another important point is that These must stay in their own groups. I have to keep track of which "commentText" was the first group and which was the 2nd group, same with "postedBy".
In the long-run I have to end up with commentText1, postedBy1, commentText2, postedBy2 all as separate String variables.
This is what I ended up doing but I just want to know if there is a better or more "proper" way to do it. I might have to put some safety if statements into this method to make sure the array gets filled properly and all that.
if let commentDict = commentsDictionary.value as? NSDictionary {
for(name, value) in commentDict {
commentInfoArray.append(value as! String)
}
let comment1Text = commentInfoArray[0]
let comment1User = commentInfoArray[1]
let comment2Text = commentInfoArray[2]
let comment2User = commentInfoArray[3]
}
If it's only postedBy and commentText relation that you are looking for try using this as your structure:-
USXhV0QYkpbSzAmXgfeteXHuoqg2 : comment1 : true,
comment2 : true,
//postedById : [postText]
Then at your retrieval use a dictionary to append your data to:-
db_Ref.child(userID).observeSingleEvent(of: .value, with: {(snap) in
if let commentDict = snap.value as? [String:AnyObject]{
for each in commentDict{
print(each.key) // Append your key here
}
}
})
I have an NSCountedSet consisting of String objects, if I iterate over the set and print it out, I see something like this:
for item in countedSet {
print(item)
}
Optional(One)
Optional(Two)
The countedSet is created from an Array of String objects:
let countedSet = NSCountedSet(array: countedArray)
If I print the array I see something like this:
["Optional(One)", "Optional(One)", "Optional(One)", "Optional(Two)", "Optional(Two)"]
Now, I want to use those counted strings to access data in a Dictionary, where the keys are String type and the values have the type [String : AnyObject]. If I print the dictionary, I see all the data.
However, if I use of the objects from the countedSet to access the dictionary, I always get a nil value back:
for item in countedSet {
let key = item as? String
let data = dictionary[key!] // Xcode forced me to unwrap key
print(data)
}
nil
nil
But
let key = "One"
let data = dictionary[key]
gives me the expected data.
What am I missing here, how can I access my data from the countedSet objects?
UPDATE: solved thanks to the comment from Martin R. The String objects were originally NSString objects (obtained from NSScanner), and I was casting them wrongly:
let string = String(originalString)
after I changed it to:
let string = (originalString as! String)
All works fine.