ios - Clipping NSString based on length + range of string -

i have large nsstring trim:

this example of long string 

first trim word or words. example, pick word "long". achieve this:

nsrange textrange = [[theentirestring lowercasestring] rangeofstring:@"long"]; nsstring *substring = //do individual word(s)?? 

which result in:

long 

however, need 10 characters in final result. in case final result want achieve is:

my long st 

as can see, evenly add characters on left , right side of word until reach desired character count, placing word or words in middle.

any appreciated.

as long string doesn't contain defined separator more once, should see right:

nsstring *string = @"this example of long string.";  nsstring *separator = @"long";  nsinteger desiredlength = 10;  nsrange range = [[string lowercasestring] rangeofstring:separator];  if(range.location != nsnotfound) {     nsinteger remainder = (desiredlength - [separator length]);      nsinteger halfremainder = (remainder / 2);      range = nsmakerange((range.location - halfremainder), (range.length + remainder));      nsstring *result = [string substringwithrange:range];      nslog(@"result: %@", result); } 

result: long st

this should customisable suit needs.

also, might worth checking halfremainder isn't trying divide odd number (i.e. 5 / 2) cast integer may cause isses out of range exceptions.