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POTruncate delimited NSString without removing delimiters
 

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  1. POTruncate delimited NSString without removing delimiters
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    <p>I have some data in an NSString, separated by colons:</p> <pre><code>@"John:Doe:1970:Male:Dodge:Durango" </code></pre> <p>I need to limit the total length of this string to 100 characters. But I also need to ensure the correct number of colons are present.</p> <p>What would be a reasonable to way to truncate the string but also add the extra colons so I can parse it into the correct number of fields on the other side?</p> <p>For example, if my limit was 18, you would end up with something like this:</p> <pre><code>@"John:Doe:1970:Ma::" </code></pre> <p>Here's an updated version of my own latest pass at this. Uses @blinkenlights algorithm:</p> <pre><code>+ (NSUInteger)occurrencesOfSubstring:(NSString *)substring inString:(NSString *)string { // http://stackoverflow.com/a/5310084/878969 return [string length] - [[string stringByReplacingOccurrencesOfString:substring withString:@""] length] / [substring length]; } + (NSString *)truncateString:(NSString *)string toLength:(NSUInteger)length butKeepDelmiter:(NSString *)delimiter { if (string.length &lt;= length) return string; NSAssert(delimiter.length == 1, @"Expected delimiter to be a string containing a single character"); int numDelimitersInOriginal = [[self class] occurrencesOfSubstring:delimiter inString:string]; NSMutableString *truncatedString = [[string substringToIndex:length] mutableCopy]; int numDelimitersInTruncated = [[self class] occurrencesOfSubstring:delimiter inString:truncatedString]; int numDelimitersToAdd = numDelimitersInOriginal - numDelimitersInTruncated; int index = length - 1; while (numDelimitersToAdd &gt; 0) { // edge case not handled here NSRange nextRange = NSMakeRange(index, 1); index -= 1; NSString *rangeSubstring = [truncatedString substringWithRange:nextRange]; if ([rangeSubstring isEqualToString:delimiter]) continue; [truncatedString replaceCharactersInRange:nextRange withString:delimiter]; numDelimitersToAdd -= 1; } return truncatedString; } </code></pre> <p>Note that I don't think this solution handles the edge case from CRD where the number of delimiters is less than the limit.</p> <p>The reason I need the correct number of colons is the code on the server will split on colon and expect to get 5 strings back.</p> <p>You can assume the components of the colon separated string do not themselves contain colons.</p>
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    1. USfunroll
    1. USfunroll
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    1. COShow the code you've tried so far.
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    2. COI'm not sure if I understood your question. You will truncate your string if it has length > 100 but you also want to add colons to reach length = 100 if it has length < 100?
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    3. COImpossible. The string of 101 colons can not be truncated by this rules.
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