How to get substring with specific ranges in Swift 4? - swift

Question

This is using the example code from the official Swift4 doc
let greeting = "Hi there! It's nice to meet you! 👋"
let endOfSentence = greeting.index(of: "!")!
let firstSentence = greeting[...endOfSentence]
// firstSentence == "Hi there!"
But lets say let greeting = "Hello there world!"
and I want to retrieve only the second word (substring) in this sentence? So I only want the word "there".
I've tried using "world!" as an argument like
let endOfSentence = greeting.index(of: "world!")! but Swift 4 Playground doesn't like that. It's expecting 'Character' and my argument is a string.
So how can I get a substring of a very precise subrange? Or get nth word in a sentence for greater use in the future?

Answer 1

You can search for substrings using range(of:).
import Foundation
let greeting = "Hello there world!"
if let endIndex = greeting.range(of: "world!")?.lowerBound {
print(greeting[..<endIndex])
}
outputs:
Hello there
EDIT:
If you want to separate out the words, there's a quick-and-dirty way and a good way. The quick-and-dirty way:
import Foundation
let greeting = "Hello there world!"
let words = greeting.split(separator: " ")
print(words[1])
And here's the thorough way, which will enumerate all the words in the string no matter how they're separated:
import Foundation
let greeting = "Hello there world!"
var words: [String] = []
greeting.enumerateSubstrings(in: greeting.startIndex..<greeting.endIndex, options: .byWords) { substring, _, _, _ in
if let substring = substring {
words.append(substring)
}
}
print(words[1])
EDIT 2: And if you're just trying to get the 7th through the 11th character, you can do this:
import Foundation
let greeting = "Hello there world!"
let startIndex = greeting.index(greeting.startIndex, offsetBy: 6)
let endIndex = greeting.index(startIndex, offsetBy: 5)
print(greeting[startIndex..<endIndex])

Answer 2

For swift4,
let string = "substring test"
let start = String.Index(encodedOffset: 0)
let end = String.Index(encodedOffset: 10)
let substring = String(string[start..<end])

Answer 3

In Swift 5 encodedOffset (swift 4 func) is deprecated.
You will need to use utf160Offset
// Swift 5
let string = "Hi there! It's nice to meet you!"
let startIndex = 10 // random for this example
let endIndex = string.count
let start = String.Index(utf16Offset: startIndex, in: string)
let end = String.Index(utf16Offset: endIndex, in: string)
let substring = String(string[start..<end])
prints -> It's nice to meet you!

Answer 4

There is one mistake in the first answer.
Range<String.Index>.upperBound
The upperBound property should be the endIndex
For Example:
let text = "From Here Hello World"
if let result = text.range(of: "Hello World") {
let startIndex = result.upperBound
let endIndex = result.lowerBound
print(String(text[startIndex..<endIndex])) //"Hello World"
}

Answer 5

the simplest way I use is :
var str = "abcdefg"
String(Array(str)[2...4])

Answer 6

Old habits die hard. I did it the "Java" way and split the string up by spaces, then accessed the second word.
print(greeting.split(separator: " ")[1]) // "there /n"