I'm trying to create a substring of the first 4 characters entered in a textField in Swift 4 on my iOS app.
Since the change to Swift 4 I'm struggling with basic String parsing.
So based on Apple documentation I'm assuming I need to use the substring.index function and I understand the second parameter (offsetBy) is the number of characters to create a substring with. I'm just unsure how I tell Swift to start at the beginning of the string.
This is the code so far:
let postcode = textFieldPostcode.text
let newPostcode = postcode?.index(STARTATTHEBEGININGOFTHESTRING, offsetBy: 4)
I hope my explanation makes sense, happy to answer any questions on this.
Thanks,
In Swift 4 you can use
let string = "Hello World"
let first4 = string.prefix(4) // Hell
The type of the result is a new type Substring
which behaves very similar to String
. However if first4
is supposed to leave the current scope – for example as a return value of a function – it's recommended to create a String
explicitly:
let first4 = String(string.prefix(4)) // Hell
See also SE 0163 String Revision 1
In Swift 4:
let postcode = textFieldPostcode.text!
let index = postcode.index(postcode.startIndex, offsetBy: 4)
let newPostCode = String(postcode[..<index])
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