Objective-C: How to extract part of a String (e.g. start with '#') - objective-c

Question

I have a string as shown below,
NSString * aString = #"This is the #substring1 and #subString2 I want";
How can I select only the text starting with '#' (and ends with a space), in this case 'subString1' and 'subString2'?
Note: Question was edited for clarity

Answer 1

You can do this using an NSScanner to split the string up. This code will loop through a string and fill an array with substrings.
NSString * aString = #"This is the #substring1 and #subString2 I want";
NSMutableArray *substrings = [NSMutableArray new];
NSScanner *scanner = [NSScanner scannerWithString:aString];
[scanner scanUpToString:#"#" intoString:nil]; // Scan all characters before #
while(![scanner isAtEnd]) {
NSString *substring = nil;
[scanner scanString:#"#" intoString:nil]; // Scan the # character
if([scanner scanUpToString:#" " intoString:&substring]) {
// If the space immediately followed the #, this will be skipped
[substrings addObject:substring];
}
[scanner scanUpToString:#"#" intoString:nil]; // Scan all characters before next #
}
// do something with substrings
[substrings release];
Here is how the code works:
Scan up to a #. If it isn't found, the scanner will be at the end of the string.
If the scanner is at the end of the string, we are done.
Scan the # character so that it isn't in the output.
Scan up to a space, with the characters that are scanned stored in substring. If either the # was the last character, or was immediately followed by a space, the method will return NO. Otherwise it will return YES.
If characters were scanned (the method returned YES), add substring to the substrings array.
GOTO 1

Answer 2

[aString substringWithRange:NSMakeRange(13, 10)]
would give you substring1
You can calculate the range using:
NSRange startRange = [aString rangeOfString:#"#"];
NSRange endRange = [original rangeOfString:#"1"];
NSRange searchRange = NSMakeRange(startRange.location , endRange.location);
[aString substringWithRange:searchRange]
would give you substring1
Read more:
Position of a character in a NSString or NSMutableString
and
http://iosdevelopertips.com/cocoa/nsrange-and-nsstring-objects.html

Answer 3

Pretty simple, easy to understand version avoiding NSRange stuff:
NSArray * words = [string componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
NSMutableArray * mutableWords = [NSMutableArray new];
for (NSString * word in words){
if ([word length] > 1 && [word characterAtIndex:0] == '#'){
NSString * editedWord = [word substringFromIndex:1];
[mutableWords addObject:editedWord];
}
}

Answer 4

Assuming that you are looking to find the first string that starts with a pound, and ends with a space, this might work. I don't have XCode in front of me, so forgive me if there's a syntax error or length off by 1 somewhere:
-(NSString *)StartsWithPound:(NSString *)str {
NSRange range = [str rangeOfString:#"#"];
if(range.length) {
NSRange rangeend = [str rangeOfString:#" " options:NSLiteralSearch range:NSMakeRange(range.location,[str length] - range.location - 1)];
if(rangeend.length) {
return [str substringWithRange:NSMakeRange(range.location,rangeend.location - range.location)];
}
else
{
return [str substringFromIndex:range.location];
}
}
else {
return #"";
}
}

Answer 5

Another simple solution:
NSRange hashtag = [aString rangeOfString:#"#"];
NSRange word = [[aString substringFromIndex:hashtag.location] rangeOfString:#" "];
NSString *hashtagWord = [aString substringWithRange:NSMakeRange(hashtag.location, word.location)];

Answer 6

This is what I'd do:
NSString *givenStringWithWhatYouNeed = #"What you want to look through";
NSArray *listOfWords = [givenStringWithWhatYouNeed componentsSeparatedByString:#" "];
for (NSString *word in listOfWords) {
if ([[word substringWithRange:NSMakeRange(0, 1)]isEqualToString:#"#"]) {
NSString *whatYouWant = [[word componentsSeparatedByString:#"#"]lastObject];
}
}
Then you can do what you need with the whatYouWant instances. If you want to know which string it is (if it's the substring 1 or 2), check the index of of word string in the listOfWords array.
I hope this helps.

Answer 7

A general and simple code to select all the words starting with "#" in a NSString is:
NSString * aString = #"This is the #substring1 and #subString2 ...";
NSMutableArray *selection=#[].mutableCopy;
while ([aString rangeOfString:#"#"].location != NSNotFound)
{
aString = [aString substringFromIndex:[aString rangeOfString:#"#"].location +1];
NSString *item=([aString rangeOfString:#" "].location != NSNotFound)?[aString substringToIndex:[aString rangeOfString:#" "].location]:aString;
[selection addObject:item];
}
if you still need the original string you can do a copy.
The inline conditional is used in case your selected item is the last word