If given a large HTML file in the form of a NSString, I need to create an array of substrings from the main string. I know what the first 4 characters of the substring will be. So basically what I have to do is seach the HTML file for those characters and return a string containing those first 4 characters and and X amount of characters after it. I then need to take every one of those substrings and put them in an array. What would be the easiest way of going about this? Thank you!