Replace character in string

Question

I have a NSMutableString @"hello". I'd like to replace the character at the second position, 'e' with 'a' so that it reads @"hallo". How do I do that?

I have tried this to implement a Shift Cipher, but it throws an IndexOutBoundsException

- (NSString*)encode:(NSString*)original withShift:(int)shift {

    NSMutableString* encoded = [NSMutableString stringWithString:original];
    for (int i=0; i < [encoded length]; i++) {
        char oriChar = [encoded characterAtIndex:i];
        if (oriChar == ' ') {
            continue;
        }
        char encChar = ((oriChar - LETTER_POS) + shift) % ALPHABET_LENGTH + LETTER_POS;

        NSRange range = {i, i};
        [encoded replaceCharactersInRange:range withString:[NSString stringWithUTF8String:&encChar]];

    }
    return encoded;

}

possible duplicate of Replacing one character in a string - iPhone/iPad — jscs
– jscs, Commented Oct 29, 2011 at 16:59

Seva Alekseyev · Accepted Answer · 2011-10-29 16:36:45Z

3

NSRange r = {1,1}; //String indexing is 0-based
[s replaceCharactersInRange: r withString:@"a"]

Also, do learn to use the online reference.

answered Oct 29, 2011 at 16:36

Seva Alekseyev

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1 Comment

zaph Over a year ago

Or use AppKiDo for reference, it's free and uses the Apple documentation.

Cesar A. Rivas · Accepted Answer · 2011-10-29 16:31:30Z

2

You can use stringByReplacingOccurrencesOfString:withString: of NSString.

answered Oct 29, 2011 at 16:31

Cesar A. Rivas

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2 Comments

siamii Over a year ago

I see. Can I replace the character only at a specified index?

Cesar A. Rivas Over a year ago

use 'stringByReplacingOccurrencesOfString:withString:options:range:' instead.

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