I know that in swift we can use Extensions to add new methods to existing classes.
But what about if i want to add a variable?
extension UIViewController {
var myVar = "xyz"
}
It gives like :
Extensions must not contain stored properties
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1Always post code, data, logs, error message, etc as text (not images) so they are searchable, and can be copied when answering. Please edit your questionAshley Mills– Ashley Mills2018-10-24 15:17:22 +00:00Commented Oct 24, 2018 at 15:17
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4in an extension you can add computed properties only – if you need a new property, inheritance is also your friend.holex– holex2018-10-24 15:17:31 +00:00Commented Oct 24, 2018 at 15:17
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Why downvote?, is it anything wrong?guru– guru2018-10-24 15:30:22 +00:00Commented Oct 24, 2018 at 15:30
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@guru : Take a look at the answer posted below which shows the work around which is being used from years to add a stored property to extension both in Objective-C world and swift world :) Lemme know if its of any help\Sandeep Bhandari– Sandeep Bhandari2018-10-24 16:57:07 +00:00Commented Oct 24, 2018 at 16:57
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4 Answers
We can't add the stored properties to extensions directly but we can have the computed variables.
extension UIViewController {
var myVar: String {
return "xyz"
}
}
Extensions in Swift can:
- Add computed instance properties and computed type properties
- ...
For more please visit
https://docs.swift.org/swift-book/LanguageGuide/Extensions.html
Comments
You can only add computed properties to extensions as follows...
extension UIViewController {
var someProperty = "xyz" : String {
return "xyz"
}
}
If you wish to use it the way you are defining it, you might need to subclass your UIViewController
class YourCustomViewController: UIViewController {
var someProperty: String = "xyz"
}
Comments
you can only use computed variables:
for example we have the type Int in swift, and we want it extend in a way that swift generates a random number from 0 to our number :
extension Int
{
var arc4random : Int{
if self > 0
{return Int(arc4random_uniform(UInt32(UInt(self))))}
else if self < 0
{return -Int(arc4random_uniform(UInt32(UInt(abs(self)))))}
else
{return 0}
}
}
and usage :
myArray.count.arc4random
here my array.count is an Int , and arc4random is the computed variable we have defined in our extension, u cant store a value in it
Comments
You can try ( This is a readOnly computed property )
extension UIViewController {
var someProperty : String {
return "xyz"
}
}
Comments
