Get the first word in a String of words & spaces - Substring first word before space

Question

I have a string that has words and spaces, "2h 3m 1s". I want to extract 2h out of it; so get everything before first space.

var date = "1,340d 1h 15m 52s"  // I want to extract "1,340d".

What is the best practice of doing it? What substring function is the best approach?

@UmaMadhavi I don't just want to get rid of the all white spaces. I want to get the characters before first space. — senty, Dec 17 '15 at 11:53
http://stackoverflow.com/a/24144365/5362916 please find this — Uma Madhavi, Dec 17 '15 at 11:55
I'd thought I'd mention that the accepted answer is *not the best approach* in this specific case. For large strings, both `split` and `componentSeparatedByString` give an unnecessary overhead when you just want the substring from start and up to a given character (" "). — dfrib, Dec 17 '15 at 13:04

Laffen · Accepted Answer · 2019-10-21T06:31:31.390

36

If your string is heavy, componentsSeparatedByString() tends to be faster.

Swift 2:

var date = "1,340d 1h 15m 52s"
if let first = date.componentsSeparatedByString(" ").first {
    // Do something with the first component.
}

Swift 3/4/5:

if let first = date.components(separatedBy: " ").first {
    // Do something with the first component.
}

edited Oct 21 '19 at 06:31

answered Dec 17 '15 at 11:58

Laffen

2,753
17
29

Better approach! Thanks a lot! – senty Dec 17 '15 at 12:03
Great answer! Just keep in mind that in this example if the date string is empty, this will crash. You can do optional chaining to avoid this. – Jonathan Cabrera Dec 05 '17 at 18:17
can this be modified to only return the first word if words are separated by new lines also? This will now work for line return. – alionthego Apr 11 '20 at 12:34

dfrib · Answer 2 · 2015-12-17T13:03:22.037

In this context, neither the .componentsSeparatedByString(" ") method nor the characters.split(" ") method is the "best approach". Both these methods will traverse the full String object, and give a String array as an result. Only after the array has been computed do we extract the first entry of this array. If we're treating a huge string, this is quite unnecessary in this context, and will result in an unnecessary overhead.

Instead, for a huge string, the following method is to prefer:

let firstDateEntryFast = date.substringToIndex((date.rangeOfString(" ")?.first)!)

This will look for the index of the first occurrence of " ", and thereafter return the substring from start of original string up only to the first occurrence. I.e., it will never investigate or make use of the original (in this context: assumed large) string beyond they point of the first " " occurrence.

You should note, however, that due to the force unwrap (operator (!)), this will crash at runtime if the string does not contain any instance of " ". So to stay safe, and follow the optional convention of Swift, use it in an if let clause:

if let myRange = date.rangeOfString(" ") {
    let firstDateEntryFast = date.substringToIndex(myRange.first!)
        // at this point, you know myRange is non-empty, and hence, .first can be
        // force-unwrapped
}
else {
    let firstDateEntryFast = date
        // no " " separation, unexpected? -> action
}

As in my first version of the answer, split can be used as an alternative (comparable with componentsSeparatedByString):

var date = "1,340d 1h 15m 52s"
let dateAsArray = date.characters.split(" ").map{ String($0) }
let firstDateEntry = dateAsArray[0]

Alternatively, skip storing them all in an array and directly get the first entry

var date = "1,340d 1h 15m 52s"
let firstDateEntryDirectly = String(date.characters.split(" ")[0])

score 5 · Answer 3 · answered Nov 18 '16 at 12:48

5

Swift 3 version

var str = "Hello, playground one two three"
let firstWord = str.components(separatedBy: " ").first

answered Nov 18 '16 at 12:48

Pavle Mijatovic

773
10
6

score 2 · Answer 4 · answered Dec 17 '15 at 11:57

2

Use below code for your requirement

var date = "1,340d 1h 15m 52s"
print((date.componentsSeparatedByString(" ") as NSArray).objectAtIndex(0));

answered Dec 17 '15 at 11:57

Narayana Rao Routhu

6,303
27
42

score 0 · Answer 5 · answered May 29 '20 at 17:27

Swift 5

var name = ""
if let optionalName = someOptionalString as? String {
    name = optionalName.contains(" ") ? (name.components(separatedBy: " ").first ?? "") : optionalName
}

First, we make sure the string is not nil. Then, we use the ternary operator to assign it accordingly based on it it contains any spaces or not.

score 0 · Answer 6 · answered May 18 '22 at 12:52

Have you tried Scanner? It's pretty fast and powerful.

var date = "1,340d 1h 15m 52s"  // I want to extract "1,340d".
let scanner = Scanner(string: date)
if let first = scanner.scanUpToCharacters(from: .whitespaces) {
    print("\(first)") // Prints "1,340d"
}

https://developer.apple.com/documentation/foundation/scanner

Get the first word in a String of words & spaces - Substring first word before space

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