How to convert text to camel case in Objective-C? - objective-c

Question

I'm making little utility to help me generate code for an app I'm making. I like to have constants for my NSUserDefaults settings, so that my code is more readable and easier to maintain. The problem is, that making constants for everything takes some time, so I'm trying to write a utility to generate code for me. I'd like to be able to enter a string and have it converted to camel case, like so:
- (NSString *)camelCaseFromString:(NSString *)input{
return inputAsCamelCase;
}
Now, the input string might be composed of multiple words. I'm assuming that I need some sort of regular expression here, or perhaps there is another way to do it. I'd like to input something like this:
#"scrolling direction"
or this:
#"speed of scrolling"
and get back something like this:
kScrollingDirection
or this:
kSpeedOfScrolling
How would you go about removing spaces and replacing the character following the space with the uppercase version?

Answer 1

- (NSString *)camelCaseFromString:(NSString *)input {
return [#"k" stringByAppendingString:[[input capitalizedString] stringByReplacingOccurrencesOfString:#" " withString:#""]];
}
Capitalize each word.
Remove whitespace.
Insert "k" at the beginning. (Not literally, but a simplification using stringByAppendingString.)

Answer 2

The currently accepted answer has a bug. (also pointed out by #jaydee3)
Words already having proper camelCasing, PascalCasing, or capitalized TLA acronyms will have their correct casing "destroyed" by having non-first characters lowercased via the call to capitalizedString.
So "I prefer camelCasing to PascalCasing for variables" would look like "iPreferCamelcasingToPascalcasingForVariables" but according to the question, should be "iPreferCamelCasingToPascalCasingForVariables"
Use the below category on NSString to create non-destructive camel and pascal casing. It also properly leaves ALL_CAPS words/acronyms in place, although that wasn't really part of the orig question.
An acronym as a first word for a camelCased string would be weird. "WTH" becomes "wTH" which looks weird. Anyway, that's an edge case, and not addressed. However, since question asker is prefixing with "k" then it "k IBM" becomes "kIBM" which looks ok to me, but would look be "kIbm" with currently accepted answer.
Use:
NSString *str = #"K computer manufacturer IBM";
NSLog(#"constant: %#", str.pascalCased);
// "constant: kComputerManufacturerIBM"
Category (class extension) code.
#implementation NSString (MixedCasing)
- (NSString *)camelCased {
NSMutableString *result = [NSMutableString new];
NSArray *words = [self componentsSeparatedByString: #" "];
for (uint i = 0; i < words.count; i++) {
if (i==0) {
[result appendString:((NSString *) words[i]).withLowercasedFirstChar];
}
else {
[result appendString:((NSString *)words[i]).withUppercasedFirstChar];
}
}
return result;
}
- (NSString *)pascalCased {
NSMutableString *result = [NSMutableString new];
NSArray *words = [self componentsSeparatedByString: #" "];
for (NSString *word in words) {
[result appendString:word.withUppercasedFirstChar];
}
return result;
}
- (NSString *)withUppercasedFirstChar {
if (self.length <= 1) {
return self.uppercaseString;
} else {
return [NSString stringWithFormat:#"%#%#",[[self substringToIndex:1] uppercaseString],[self substringFromIndex:1]];
}
}
- (NSString *)withLowercasedFirstChar {
if (self.length <= 1) {
return self.lowercaseString;
} else {
return [NSString stringWithFormat:#"%#%#",[[self substringToIndex:1] lowercaseString],[self substringFromIndex:1]];
}
}
#end

Answer 3

Just use: #"This is a sentence".capitalizedString;
Becomes: >> "This Is A Sentence"
Replace spaces and manipulate...
Uppercases first char of word, and lowers the other letters for each word.