I have two NSMutableArray's
I am trying to remove the MutableArray from other Array with removeObjectsInArray() method
Here is my code:
arrayImage.removeObjectsInArray(arrayDeleteImage)
But it requires a filter (NSPredicate), I don't understand why it's requried.. I have implement the filter but it's giving me an error..
arrayImage = arrayImage.filter //error:Nsmutable does not have member filter
{ value in
!contains(arrayDeleteImage, value) //Implicit use of 'self' in closure; use 'self.' to make capture semantics explicit
}
How can I remove the array objects from the other array ?
Try this:
var arrayOne:[NSMutableArray]
var arrayTwo:[NSMutableArray]
for ar in arrayTwo
{
arrayOne.removeObject(ar)
}
Related
I want to initialise elements only if an array has been set from outside the current class. Looks like a use for didSet!
// external API
var arr: [Display] = [] {
didSet {
array = arr
initialiseElements(arr: arr)
}
}
// internal
private var array: [Display] = []
but when we return the value from arr it might not be correct - I want to use array as a backing store.
I tried to use a getter on arr but this isn't allowed in Swift. How can I prevent the use of arr within the class, or otherwise ensure we only initiliseElements(:) via calls outside the class?
Why use didSet? why not set?
var arr: [Display] {
set {
array = newValue
initialiseElements(arr: newValue)
}
get {
return self.array
}
}
How can I prevent the use of arr within the class?
You can't, swift doesn't have such access control
otherwise ensure we only initiliseElements(:) via calls outside the class
Again, you can't.
It makes no sense logically as well, think of what you are asking for, you are asking class to declare a variable which itself cant set (read only) but should expose to it outside class to write (read + write) it?
How is that possible? What is the use case you are trying to solve here? If for some reason you ended up with this solution, may be solutioning is wrong! re think of your implementation.
Hope this helps
I am new to swift and I am using swift 4.0. I have a class with computed property of type Dictionary. I am using getter and setter for this property. Below is my property snippet.
var responses:[String:Float] {
get {
let newresponses = self.calculateResponses(with: self.Range)
return newresponses
}
set {
}
}
How do I code setter so it allows me to update value for specific key? For example, in one of my func I need to update value for responses for a specific key.
self. responses[key] = newResponse
Thank you.
You can't do this with computed property. Because every time you're trying to get responses you're actually getting result of self.calculateResponses(with: self.Range).
To solve this just create empty dictionary
var responses = [String : Float]()
and then when you need to assign new value use this
responses[key] = newResponse
or if you need to assign all new dictionary use this
responses = self.calculateResponses(with: self.Range)
I want to create a dictionary out of an array and assign a new custom object to each of them. I'll do stuff with the objects later. How can I do this?
var cals = [1,2,3]
// I want to create out of this the following dictionary
// [1:ReminderList() object, 2:ReminderList() object, 3:ReminderList() object]
let calendarsHashedToReminders = cals.map { ($0, ReminderList()) } // Creating a tuple works!
let calendarsHashedToReminders = cals.map { $0: ReminderList() } // ERROR: "Consecutive statements on a line must be separated by ';'"
map() returns an Array so you'll either have to use reduce() or create the dictionary like this:
var calendars: [Int: ReminderList] = [:]
cals.forEach { calendars[$0] = ReminderList() }
You can also use reduce() to get a oneliner but I'm not a fan of using reduce() to create an Array or a Dictionary.
I have a dictionary declared like this:
var myDict = [Int : [Int]]()
The array in it is not initialized, so every time I have to check it first:
if (myDict[idx] == nil) {
myDict[idx] = []
}
How to initialize it as an empty array in MyDict declaration?
I think you could be misunderstanding something pretty key - let's make sure:
The way the dictionary works, is not to have one array, but an array for each key.
Each value of 'idx' you request the array for returns a different array.
You can't expect it to return an empty array - a dictionary is meant to return a nil value for a key that hasn't been set. To do what you're trying, the following would probably do the trick:
myDict[idx] = myDict[idx] ?? []
That's what dictionary do if you try to retrieve a key for which no value exists.
You can subclass Dictionary and override the subscript func to get what you want like this. Or simply write an extension, or write a operator defination to use a different symbol.
“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. ”
Excerpt From: Apple Inc. “The Swift Programming Language (Swift 2.1).” iBooks. https://itunes.apple.com/cn/book/swift-programming-language/id881256329?l=en&mt=11
You can initialize it this way
myDict.forEach {
(var dictElement) -> () in
dictElement.1 = [Int]()
}
I am now writing a program involves class and dictionaries. I wonder how could I access a class's values inside a dictionary. For the code below how do I access the test1 value using the dictionary. I have tried using dict[1].test1but it doesn't work.
class test {
var tes1 = 1
}
var refer = test()
var dict = [1:refer]
There are a few problems with the line dict[1].test1:
Firstly, the subscript on a dictionary returns an optional type because there may not be a value for the key. Therefore you need to check a value exists for that key.
Secondly, in your class Test you've defined a variable tes1, but you're asking for test1 from your Dictionary. This was possibly just a type-o though.
To solve these problems you're code should look something like this:
if let referFromDictionary = dict[1] {
prinln(referFromDictionary.test1)
}
That's because the subscript returns an optional, so you have to unwrap it - and the most straightforward way is by using optional chaining:
dict[1]?.tes1
but you can also use optional binding:
if let test = dict[1] {
let value = test.tes1
}