I just wrote the following code:
var results:[[String:[Int:String]]] = [Dictionary<String, Dictionary<Int,String>>()]
results.removeAll(keepCapacity: false)
results.append(["Swift":[1:"I love you"]])
print(results)
var dict = results[0]
var key = dict[dict.startIndex].0
var updateValue = [2:"I want to marry you"]
var value = dict.updateValue(updateValue, forKey: key)
print(results)
But I found that it doesn't work as expected. The final print still outputs
[[Swift: [1: I love you]]]. and dict.updateValue did succeed!
Welcome to the world of copy semantics. When you take the first item out of your array with results[0], you aren't making a reference to it, you're taking a copy of the value instead. This means that the Dictionary that you're updating is not the one inside the array.
After you make your updates, just replace the first value in the array with your modified one.
var value = dict.updateValue(updateValue, forKey: key)
results[0] = dict
print(results) // "[[Swift: [2: I want to marry you]]]"
Related
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.
Ok, I am working in an iMessage app and am trying to parse more than 1 url query item from the selected message here- I have been successful getting/sending just 1 value in a query:
override func willBecomeActive(with conversation: MSConversation) {
// Called when the extension is about to move from the inactive to active state.
// This will happen when the extension is about to present UI.
if(conversation.selectedMessage?.url != nil) //trying to catch error
{
let components = URLComponents(string: (conversation.selectedMessage?.url?.query?.description)!)
//let val = conversation.selectedMessage?.url?.query?.description
if let queryItems = components?.queryItems {
// process the query items here...
let param1 = queryItems.filter({$0.name == "theirScore"}).first
print("***************=> GOT IT ",param1?.value)
}
}
When I just have 1 value, just by printing conversation.selectedMessage?.url?.query?.description I get an optional with that 1 value, which is good. But with multiple I cant find a clean way to get specific values by key.
What is the correct way to parse a URLQueryItem for given keys for iMessage?
When you do conversation.selectedMessage?.url?.query?.description it simply prints out the contents of the query. If you have multiple items then it would appear something like:
item=Item1&part=Part1&story=Story1
You can parse that one manually by splitting the string on "&" and then splitting the contents of the resulting array on "=" to get the individual key value pairs in to a dictionary. Then, you can directly refer to each value by key to get the specific values, something like this:
var dic = [String:String]()
if let txt = url?.query {
let arr = txt.components(separatedBy:"&")
for item in arr {
let arr2 = item.components(separatedBy:"=")
let key = arr2[0]
let val = arr2[1]
dic[key] = val
}
}
print(dic)
The above gives you an easy way to access the values by key. However, that is a bit more verbose. The way you provided in your code, using a filter on the queryItems array, is the more compact solution :) So you already have the easier/compact solution, but if this approach makes better sense to you personally, you can always go this route ...
Also, if the issue is that you have to write the same filtering code multiple times to get a value from the queryItems array, then you can always have a helper method which takes two parameters, the queryItems array and a String parameter (the key) and returns an optional String value (the value matching the key) along the following lines:
func valueFrom(queryItems:[URLQueryItem], key:String) -> String? {
return queryItems.filter({$0.name == key}).first?.value
}
Then your above code would look like:
if let queryItems = components?.queryItems {
// process the query items here...
let param1 = valueFrom(queryItems:queryItems, key:"item")
print("***************=> GOT IT ", param1)
}
You can use iMessageDataKit library. It makes setting and getting data really easy and straightforward like:
let message: MSMessage = MSMessage()
message.md.set(value: 7, forKey: "user_id")
message.md.set(value: "john", forKey: "username")
message.md.set(values: ["joy", "smile"], forKey: "tags")
print(message.md.integer(forKey: "user_id")!)
print(message.md.string(forKey: "username")!)
print(message.md.values(forKey: "tags")!)
(Disclaimer: I'm the author of iMessageDataKit)
In my code I need to retrieve a saved array of data to populate student history data. I am using the following line of code - which works great.
returnedArray = UserDefaults.standard().object(forKey: "studentHistoryArray")! as! NSArray as! [[String]]
The problem I have is on the initial (first) run of the program. The array hasn't been created/saved yet so I need to skip this step, but only on the initial run of the program. Is there a way to run this line of code only on the first run of a program?
var defaults = UserDefaults.standard()
let studentHistoryArrayKey = "studentHistoryArray"
var returnedArray = defaults.object(forKey: studentHistoryArrayKey) as? [[String]]
// I don't think that you need to use the intermediary cast to NSArray, but
// I could be wrong.
if returnedArray == nil {
returnedArray = [[String]]()
defaults.setObject(returnedArray, forKey: studentHistoryArrayKey)
}
// Now it's guaranteed to be non-nil, so do whatever you need to do with the array.
As a rule of thumb, if you're using ! as liberally as in your example, something's going to break.
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.
I have this block of code
//start of the loop
if let objects = objects as? [PFObject] {
for object in objects {
//saving the object
self.likerNames.setObject(object["fromUserName"]!, forKey: saveStatusId!)
}
}
likerNames is an NSMutableArray declared earlier, saveStatusId is a string I also declared and saved earlier (It's just an objectId as a String), and object["fromUserName"] is an object returned from my query (not shown above).
Everything is working fine as it is but my query sometimes returns more than one object["fromUserName"] to the same key which is saveStatusId. When this happens the value I have for that saveStatusId is replaced when I actually want it to be added to the key.
So want it to kind of look like this
("jKd98jDF" : {"Joe", "John"})
("ksd6fsFs" : {"Sarah"})
("payqw324" : {"Chris", "Sarah", "John"})
I know you can use Arrays but I'm not sure how I would go about that to get it to work in my current situation.
So my question would be how to I get my key (saveStatusId) to store more than one value of object["fromUserName"]?
Something like this could work
let key = saveStatusId!
let oldValue = self.likerNames.objectForKey( key ) as? [String]
let newValue = (oldValue ?? []) + [ object["fromUserName" ] ]
self.likerNames.setObject( newValue, forKey: key )
If likerNames has an array in slot[saveStatusId], append the new value, otherwise create an array and put that in the right slot