Replace only the first instance of a substring in an NSString

Question

So if you have an NSString that goes:

@"My blue car is bigger than my blue shoes or my blue bicycle";

I would like a method that replaces only the first instance of blue with green, to produce:

@"My green car is bigger than my blue shoes or my blue bicycle";

How does one do this?

score 63 · Accepted Answer · edited May 05 '17 at 13:00

63

Assuming the following inputs:

NSString *myString = @"My blue car is bigger then my blue shoes or my blue bicycle";
NSString *original = @"blue";
NSString *replacement = @"green";

The algorithm is quite simple:

NSRange rOriginal = [myString rangeOfString:original];

if (NSNotFound != rOriginal.location) {
    myString = [myString stringByReplacingCharactersInRange:rOriginal withString:replacement];
}

edited May 05 '17 at 13:00

Iulian Onofrei

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answered Dec 22 '11 at 18:44

Jonathan Grynspan

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Another pass with `original = @"then"` `replacement = @"than"` might also be advisable. – jscs Dec 22 '11 at 19:48
3

Not my problem if the original string has typos. ;p – Jonathan Grynspan Dec 22 '11 at 19:50
Crashes when `original` is `nil` – fabb Sep 17 '15 at 13:04
Great for performance when you know there is (at most) only an occurrence of each replace target. – Nicolas Miari Feb 03 '16 at 10:45

Kevin Sabbe · Answer 2 · 2019-02-18T02:29:51.480

27

SWIFT 3 and 4 UPDATE:

extension String 
{
    func stringByReplacingFirstOccurrenceOfString(
            target: String, withString replaceString: String) -> String
    {
        if let range = self.range(of: target) {
            return self.replacingCharacters(in: range, with: replaceString)
        }
        return self
    } 
}

edited Feb 18 '19 at 02:29

answered Nov 29 '16 at 10:35

Kevin Sabbe

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Works perfectly in Swift 4.2 as well – Adam S. Feb 03 '19 at 18:34

score 13 · Answer 3 · answered Oct 14 '19 at 13:44

A more Swift'y version of the implementations posted here. This one matches the syntax replacingOccurrences(of:with:) in Swift 5.1

extension String {

    func replacingFirstOccurrence(of target: String, with replacement: String) -> String {
        guard let range = self.range(of: target) else { return self }
        return self.replacingCharacters(in: range, with: replacement)
    }
}

An example of usage:

let string = "I like bacon, please give me some more bacon!"
let newString = string.replacingFirstOccurrence(of: "bacon", with: "meat")

score 10 · Answer 4 · answered Oct 18 '17 at 09:54

10

Swift 4 version:

func replacingFirstOccurrence(of string: String, with replacement: String) -> String {
    guard let range = self.range(of: string) else { return self }
    return replacingCharacters(in: range, with: replacement)
}

answered Oct 18 '17 at 09:54

Daniel Saidi

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Luca Davanzo · Answer 5 · 2016-11-29T20:45:46.247

In Swift is useful extends String in this way:

public extension String {

    func stringByReplacingFirstOccurrenceOfString(target: String, withString replaceString: String) -> String {
        if let range = self.rangeOfString(target) {
            return self.stringByReplacingCharactersInRange(range, withString: replaceString)
        }
        return self
    }

}

In this way you can call wherever:

let s = "The red red cat".stringByReplacingFirstOccurrenceOfString("red", withString: "fat")
print(s) // "The fat red cat"

score 2 · Answer 6 · answered Dec 22 '11 at 18:43

2

  NSString *initialString = @"My blue car is bigger then my blue shoes or my blue bicycle";
  NSRange range = [initialString rangeOfString:@"blue"];
  NSString *replacedString = [initialString stringByReplacingCharactersInRange:range withString:@"green"];
  NSLog(@"replacedString: %@", replacedString);

answered Dec 22 '11 at 18:43

Eugene

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This will fail with an exception if `initialString` does not contain `@"blue"`. – Jonathan Grynspan Dec 22 '11 at 19:31

score 0 · Answer 7 · answered Aug 06 '14 at 09:00

-(NSString*) replaceFirstOccuarnceFromString: (NSString*)input withOriginal:(NSString*) original AndReplacment:(NSString*)replacement
{
    NSRange rOriginal = [input rangeOfString: original];
    if (NSNotFound != rOriginal.location) {
        input = [input
                    stringByReplacingCharactersInRange: rOriginal
                    withString:                         replacement];
    }
    return input;
}

score 0 · Answer 8 · answered Dec 22 '11 at 18:44

First locate the substring, and then make the replacement. Example :

NSString *aString = @"foo bar foo";
NSRange firstFooRange = [aString rangeOfString:@"foo"];
NSString *anotherString = [aString stringByReplacingOccurrencesOfString:@"foo"
                                                             withString:@"bar"
                                                                options:0
                                                                  range:firstFooRange];

NSString documentation.

Using `stringByReplacingOccurrencesOfString:` is unnecessary here, because in `firstFooRange` is only one single occurrence. Use `stringByReplacingCharactersInRange:` instead. — AppsolutEinfach, Oct 28 '16 at 09:24

Replace only the first instance of a substring in an NSString

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