Hello Everyone I am new in swift and In my app I declare a dictionary like this :
var imageDict : Dictionary<String, String> = [:]
and I want to set values for that dictionary like this :
imageDict.setValue(NSStringFromCGPoint(frame), forKey: NSString.stringWithString("/(tagValue)"));
But I got error like this :
Dictonary <String, String> does not have a member named 'setValue'
This question is from my previous question and can enybody explain my why I can not set value for that dictionar and can enybody tell me any other way to do that?
Thanks In advance.
Swift dictionary does not have method like setValue:forKey:. Only NSMutableDictionary has such methods. If you wish to assign value for key in swift, you should use subscripting. Here is the correct way to do it, if you wish to do it with swift dictionary.
var imageDict:[String: String] = [:]
imageDict["\(tagValue)"] = NSStringFromCGRect(frame)
Or if you wish to use NSMutableDictionary then, it looks like this,
var imageDict = NSMutableDictionary()
imageDict.setObject(NSStringFromCGRect(frame), forKey: "\(tagValue)")
I guess you need to use NSMutableDictionary.
Related
Is this proper syntax for this line of code? If not what would be the correct syntax and why so?
UserDefaults.standard.dictionary(forKey: "mainDict")?.updateValue(subDict, forKey: "subDictTitle")
First, you have to store Userdefault dictionary to a temporary dictionary. Then you have to add data to a temporary dictionary.
No need to update the dictionary to Userdefault. When you store Dictionary to the Usedefault with the same key, it will replace the older dictionary to the new one.
UserDefaults.standard.set(YOUR_TEMPORARY_DICTIONARY, forKey: YOUR_KEY_NAME)
The updateValue(_:forKey:) is a mutating instance method for the dictionary, which means that it updates the value of the dictionary. Obviously, In order to mutate an instance, it has to be mutable, which is not the case when calling UserDefaults.standard.dictionary(forKey: "mainDict").
Even if you did:
let myDict = ["k1": "Hello"]
UserDefaults.standard.register(defaults: ["myDict": myDict])
var mutable = UserDefaults.standard.dictionary(forKey: "myDict")!
mutable["k1"] = "HEY"
print(UserDefaults.standard.dictionary(forKey: "myDict")) // Optional(["k1": Hello])
the value of the dictionary set in the user default won't change because simply mutable is a copy of it.
To clarify, it's similar to implementing:
UserDefaults.standard.register(defaults: ["k2": "this is my string"])
UserDefaults.standard.string(forKey: "k2") = "new string"
which generates the error of
Expression is not assignable: function call returns immutable value
So, in order to resolve this issue, what you should do is to set a new value (updated dictionary) to the user defaults with the same key:
var myDict = UserDefaults.standard.dictionary(forKey: "myDict")
myDict?.updateValue("Hey", forKey: "k1")
UserDefaults.standard.set(myDict, forKey: "myDict")
I have a dictionary, something like this
var dict = [String : [String]]()
The functionality I want to achieve is that, I have a hashtable which I can quick get the list of data from.
In my code, I use a dictionary and an array.
I am not very good with algorithem and data structure, so I am wondering if there is any better data structure that is suitable for something like this?
Use:
var dict = [String : [String]]()
Swift already has built in search algorithms that allow you you to retrieve data inside of your dictionary with simple subscript syntax like so
dict["element"]
You will use it in this way -
Declaration:
var dict: [String: [String]] = [:]
Initialise:
dict["element"] = myArray
What is the right way to cast Dictionary in Swift 3 to a CFDictionary? Is it legal to write like this?
var dictionary:Dictionary<NSString, Int> = [:]
and then
dictionary as CFDictionary
Yes you can do that. your solution will work and you can also do it like this.
var dictionary = [
key:value
] as CFDictionary
You can refer further from here
I'm trying to save a dictionary to NSUserDefaults using the setObject() function but when I use the objectForKey() function to retrieve the dictionary it returns nil. Why is this happening?
var data = NSUserDefaults.standardUserDefaults();
var scoreboard = [Int : String]()
let scores = "scoresKey"
scoreboard[3] = "spencer"
scoreboard[6] = "brooke"
scoreboard[11] = "jason"
data.setObject(scoreboard, forKey: scores)
data.objectForKey(scores) // Returns nil
The first problem was that it's not possible to use NSUserDefaults in a Playground.
See: https://stackoverflow.com/a/31210205/3498950
A second problem is found when the code above runs in a normal iOS project. It throws an NSInvalidArgumentException since the dictionary was a non-property list object because the keys needed to be of type String.
Although NSDictionary and CFDictionary objects allow their keys to be
objects of any type, if the keys are not string objects, the
collections are not property-list objects.
See: "What is a Property List?" in the Apple Docs
I was having trouble storing a Dictionary in the NSUserDefaults, and then I had trouble retrieving the values. After a failed search on the web, I finally figured it out and so I hope this helps you with this same issue.
Define your variables for NSUserDefaults, Dictionary and key:
let defaults = NSUserDefaults.standardUserDefaults()
var myDictionary = Dictionary<String, Int>()
let myKey = "Key"
How to save your dictionary:
defaults.setObject(myDictionary, forKey: myKey)
How to retrieve your dictionary:
myDictionary = defaults.dictionaryForKey(myKey) as! Dictionary<String, Int>
NOTE: make sure that your data types are the same as the way you set them up.
*** FYI, this is using Xcode 6.3.2