Swift: How to get substring from start to last index of character

Just accessing backward

The best way is to use substringToIndex combined to the endIndexproperty and the advance global function.

var string1 = "www.stackoverflow.com"

var index1 = advance(string1.endIndex, -4)

var substring1 = string1.substringToIndex(index1)

Looking for a string starting from the back

Use rangeOfString and set options to .BackwardsSearch

var string2 = "www.stackoverflow.com"

var index2 = string2.rangeOfString(".", options: .BackwardsSearch)?.startIndex

var substring2 = string2.substringToIndex(index2!)

No extensions, pure idiomatic Swift

Swift 2.0

advance is now a part of Index and is called advancedBy. You do it like:

var string1 = "www.stackoverflow.com"

var index1 = string1.endIndex.advancedBy(-4)

var substring1 = string1.substringToIndex(index1)

Swift 3.0

You can’t call advancedBy on a String because it has variable size elements. You have to use index(_, offsetBy:).

var string1 = "www.stackoverflow.com"

var index1 = string1.index(string1.endIndex, offsetBy: -4)

var substring1 = string1.substring(to: index1)

A lot of things have been renamed. The cases are written in camelCase, startIndex became lowerBound.

var string2 = "www.stackoverflow.com"

var index2 = string2.range(of: ".", options: .backwards)?.lowerBound

var substring2 = string2.substring(to: index2!)

Also, I wouldn’t recommend force unwrapping index2. You can use optional binding or map. Personally, I prefer using map:

var substring3 = index2.map(string2.substring(to:))

Swift 4

The Swift 3 version is still valid but now you can now use subscripts with indexes ranges:

let string1 = "www.stackoverflow.com"

let index1 = string1.index(string1.endIndex, offsetBy: -4)

let substring1 = string1[..<index1]

The second approach remains unchanged:

let string2 = "www.stackoverflow.com"

let index2 = string2.range(of: ".", options: .backwards)?.lowerBound

let substring3 = index2.map(string2.substring(to:))

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