Extensions add new functionality to an existing class, structure, or enumeration type.
Apple Pre-release Docs
Questions tagged [swift-extensions]
394 questions
2
votes
1 answer
Idiomatic way to test Swift Optionals
I'm NOT asking if these extensions are a good idea or not, it's just a thought experiment, I'm trying to learn from the practice.
Agreeing with Christian Lattner, that methods are generally preferable, I thought I'd play with being able to…
Travis Griggs
- 21,522
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2
votes
1 answer
Swift 2.1 Array Extension objectsAtIndexes
I'm trying to extend an array to return only objects at certain indexes. The map function seemed to be the best choice for me here.
extension Array {
func objectsAtIndexes(indexes: [Int]) -> [Element?]? {
let elements: [Element?] =…
Ron
- 1,610
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2
votes
1 answer
Protocol Extension type Self does not match initializer types
Let's say for academic purposes, I would prefer an expression like
someInt.asDouble
rather than the stock
Double(someInt)
Since all of the various Swift integer types conform to the IntegerType protocol AND because there seems to be a Double()…
Travis Griggs
- 21,522
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- 91
- 167
2
votes
1 answer
Swift extension in Cocoapods Framework causing Unrecognised Selector sent to Class
I have a Swift framework which is managed via Cocoapods and contains an extension like so:
public extension UIImage {
public static func maskedImageWithColor( color: UIColor, forImageNamed image: UIImage) {
// Implementation
…
Simon Fairbairn
- 65
- 8
2
votes
4 answers
Extend Swift Array to Filter Elements by Type
How can a swift array be extended to access members of a particular type?
This is relevant if an array contains instances of multiple classes which inherit from the same superclass. Ideally it would enforce type checking appropriately.
Some…
Anthony Mattox
- 7,048
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- 59
2
votes
1 answer
Extending Dictionary with key and value constraints
I want to extend dictionary and constrain it to specific key type of NSDate with values of type Array
MyClass is a swift class with no subclass.
extension Dictionary where Key: NSDate, Value: Array{
func myFunction() -> Int{
…
the Reverend
- 12,305
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- 121
2
votes
1 answer
Complicated Swift Extension
I want to create an extension for the String class in Swift that allows you to get a substring via the subscript operator like in Python. This can be accomplished with the Range class in the following way
extension String {
subscript (range:…
bjornorri
- 369
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2
votes
1 answer
Extension function asking for return type instead of parameter
I am creating an extension of UIFont in Swift that will return a custom font.
import UIKit
extension UIFont {
func museoSansRounded900(size: CGFloat) -> UIFont {
return UIFont(name: "MuseoSansRounded900", size: size)!
}
}
However, when I…
SleepNot
- 2,982
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- 72
2
votes
0 answers
Swift Array extension only for certain type of Array
If I want to make an Array extension, but only do an extension for an Array of type [UIView], is that possible in Swift?
Currently I'm just doing a normal extension Array with a precondition that the Array only holds elements of type UIView, but it…
Adam Johns
- 35,397
- 25
- 123
- 176
2
votes
0 answers
Adding optional method of objective-C class to swift extension
To an already extensive Objective-C app I wanted to add Core Data functionality. Recent additions are in Swift, and this worked well, up until now.
Because my Objective-C AppDelegate already contains quite some stuff, I decided to write a Swift…
VanFruniken
- 21
- 3
2
votes
1 answer
Swift extension declaration error: "declaration only valid at file scope"
I'm trying to create a simple Swift extension containing a calculated property. I don't understand why I'm getting this compile error (“declaration only valid at file scope”). The error is at the beginning of the "private extension OpStack" line.…
stateofgary
- 25
- 6
2
votes
1 answer
Swift struct extension function - "Cannot assign to 'origin' in 'self'"
Structs in Swift can contain functions and can have extensions. Cool! Looks like a neat way to make this function available to more classes and to reduce argument passing. Here's the way the function originally looked in a map view controller:
…
Adam Eberbach
- 12,309
- 6
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- 114
2
votes
1 answer
Generalized type constraints with Swift
As an exercise, I'm trying to extend Array in Swift to add a sum() member function. This should be type safe in a way that I want a call to sum() to compile only if the array holds elements that can be added up.
I tried a few variants of something…
Jean-Philippe Pellet
- 59,296
- 21
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- 234
2
votes
1 answer
Swift Extension, Missing Argument For Parameter #1 In Call
I'll keep this as short and simple as I can.
I have an NSDate extension that I use for a number of things throughout my app, but I have run into a problem with (strangely) a very simple function.
The relevant part of the extension is:
import…
Loic Verrall
- 985
- 15
- 25
2
votes
1 answer
Immutable value of type `Int` only has mutating members named adjust
I'm learning Swift language now a days.
In Apple's documentation I saw a example for extension like:
extension Int: ExampleProtocol {
var simpleDescription: String {
return "The number \(self)"
}
mutating func adjust() {
…
Midhun MP
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