How to replace a case insensitive string in objective-c iphone?

Question

I have a long string of some characters. I want to replace some chars with other chars.

For example

string1="Hello WORLD12";
string2="world";

string1= search string2 in string1 and replace it; 
//need this method in objective c

string1="Hello world12"; 

Answer 1

Use NSRange to grab the replacing string and then usestringByReplacingOccurrencesOfString function to replace the characters in string.

NSString *string1 = "Hello WORLD12";
NSString *string2 = "world";
NSRange *range = [string1 rangeOfString:string2];
if (range.length > 0){
    NSString *newString = [string1 substringFromIndex:range.location+6];
    [string1 stringByReplacingOccurrencesOfString:newString withString:string2];
}