Swift : How to get the string before a certain character?

Question

How do I get the string before a certain character in swift? The code below is how I did it in Objective C, but can\'t seem to perform the same task in Swift. Any tips or su

Answer 1

Use componentsSeparatedByString() as shown below:

var delimiter = " "
var newstr = "token0 token1 token2 token3"
var token = newstr.components(separatedBy: delimiter)
print (token[0])

Or to use your specific case:

var delimiter = " token1"
var newstr = "token0 token1 token2 token3"
var token = newstr.components(separatedBy: delimiter)
print (token[0])

Answer 2

Swift 5 extensions

extension String {
    func stringBefore(_ delimiter: Character) -> String {
        if let index = firstIndex(of: delimiter) {
            return String(prefix(upTo: index))
        } else {
            return ""
        }
    }
    
    func stringAfter(_ delimiter: Character) -> String {
        if let index = firstIndex(of: delimiter) {
            return String(suffix(from: index).dropFirst())
        } else {
            return ""
        }
    }
}

let str = "n1:lolz"
print(str.stringBefore(":")) // n1
print(str.stringAfter(":")) // lolz

let str = "n1:"
print(str.stringBefore(":")) // n1
print(str.stringAfter(":")) // empty string

let str = "n1+lolz"
print(str.stringBefore(":")) // empty string
print(str.stringAfter(":")) // empty string

This should be fine tuned for your needs and edge cases.

Answer 3

To mutate a String into the part until the first appearance of a specified String you could extend String like this:

extension String {

    mutating func until(_ string: String) {
        let components = self.components(separatedBy: string)
        self = components[0]
    }

}

This can be called like this then:

var foo = "Hello Swift"
foo.until(" Swift") // foo is now "Hello"

Answer 4

You could use the method prefix(upTo:) in Swift 4 or above

var string = "hello Swift"
if let index = string.firstIndex(of: " ") {
    let firstPart = string.prefix(upTo: index)
    print(firstPart) // print hello
}

Answer 5

My 2 cents :-) using Swift 3.0, similar to PHP strstr

extension String {

    func strstr(needle: String, beforeNeedle: Bool = false) -> String? {
        guard let range = self.range(of: needle) else { return nil }

        if beforeNeedle {
            return self.substring(to: range.lowerBound)
        }

        return self.substring(from: range.upperBound)
    }

}

Usage1

"Hello, World!".strstr(needle: ",", beforeNeedle: true) // returns Hello

Usage2

"Hello, World!".strstr(needle: " ") // returns World!

Answer 6

Following up on Syed Tariq's answer: If you only want the string before the delimiter (otherwise, you receive an array [String]):

var token = newstr.components(separatedBy: delimiter).first