String Trimming with Certain keyword - objective-c

Question

I have a string like below.
<br><br><br><br><br> SomeHtmlString <br><br><br><br><br>
I want to remove br tags like trim function preserving middle br tags in SomeHtmlString.
Is there any function to do this shortly?
e.g.
<br><br><br>test1<br><br>test2<br><br><br><br>
to
test1<br><br>test2

Answer 1

Here is a method using regular expressions. It matches only one at a time and replaces that either at the beginning of end of the string.
NSMutableString *replaceMe = [[NSMutableString alloc ]
initWithString:#"<br><br > <br > test<br>test2<br><br>"];
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:#"^ *<br *> *"
options:NSRegularExpressionCaseInsensitive
error:&error];
do {
;
} while ([regex replaceMatchesInString:replaceMe options:NSMatchingCompleted range:NSMakeRange(0, replaceMe.length) withTemplate:#""] != 0);
regex = [NSRegularExpression
regularExpressionWithPattern:#" *<br *> *$"
options:NSRegularExpressionCaseInsensitive
error:&error];
do {
;
} while ([regex replaceMatchesInString:replaceMe options:NSMatchingCompleted range:NSMakeRange(0, replaceMe.length) withTemplate:#""] != 0);
NSLog(#"string=%#", replaceMe);
and that does strip "<br><br > <br > test<br>test2<br><br>" down to test<br>test2.
It's probably not the neatest solution but it is very easy to modify to match different expressions, with different whitespace, for example.
It's also possible to use the regular expressions to match several <br>s in one go:
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:#"^ *(<br *> *)+"
options:NSRegularExpressionCaseInsensitive
error:&error];
[regex replaceMatchesInString:replaceMe options:NSMatchingCompleted range:NSMakeRange(0, replaceMe.length) withTemplate:#""];
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:#" *(<br *> *)+$"
options:NSRegularExpressionCaseInsensitive
error:&error];
[regex replaceMatchesInString:replaceMe options:NSMatchingCompleted range:NSMakeRange(0, replaceMe.length) withTemplate:#""];
which avoids the looping but is a little harder to modify.

Answer 2

You can do this:
NSString* htmlString= #"<br><br><br><br><br> SomeHtmlString <br><br><br><br><br>";
NSString* pureString= [htmlString stringByReplacingOccurrencesOfString: #"<br>" withString: #""];
So you'll have #" SomeHtmlString " in pureString.

Answer 3

You could use this to strip out the unwanted bits:
[yourString stringByReplacingOccurrencesOfString:#"<br>" withString:#""];
Then you would use something like this to remake your string the way you want it:
NSString *newString = [NSString stringWithFormat:#"<br>%#<br>", yourString];
You might also want to look at stringByTrimmingCharactersInSet:
There are so many things you can do with NSString. Check out the Class Reference: https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/Reference/NSString.html
EDIT:
substringToIndex: could be your friend here. You can do this to find out if the first 4 characters of your string consist of the characters you want to remove:
NSString *subString = [yourString substringToIndex:4];
if ([subString isEqualToString:#"<br>"]) {
yourString = [yourString substringFromIndex:4];
}
Then you are creating a new string without those 4 characters. You keep doing this until the first 4 character are not equal to the ones you want to remove.
You can do something similar at the end of your string using substringFromIndex. You will need to know the length of your original string to make sure none of your substrings go out of bounds.

Answer 4

Alternative regular expression rendition:
NSString *input = #"<br><br><br><br><br><br>test<br>test2<br><br><br><br><br><br><br><br><br><br>";
__block NSString *output;
NSError *error;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"^(<br>)*(.*?)(<br>)*$"
options:NSRegularExpressionCaseInsensitive
error:&error];
[regex enumerateMatchesInString:input
options:0
range:NSMakeRange(0, [input length])
usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
NSRange matchRange = [result rangeAtIndex:2];
output = [input substringWithRange:matchRange];
}];
if (output)
NSLog(#"Found: %#", output);