Remove part in Objective-C

In Objective-C, NSString is the primary class for working with strings. To remove part of a string in Objective-C, we can use the stringByReplacingOccurrencesOfString:withString: method. This method replaces all occurrences of a specified string with another string.

Here is an example:

NSString *string = @"Hello, world!";
NSString *substring = @"world";
NSString *newString = [string stringByReplacingOccurrencesOfString:substring withString:@""];
NSLog(@"%@", newString);

In the above example, we used the stringByReplacingOccurrencesOfString:withString: method to remove the "world" substring from the original string "Hello, world!". The resulting string, stored in the newString variable, is "Hello, !".

We can also specify options to control the search behavior, such as case-sensitivity or search direction. For example, the following code removes the first occurrence of the "world" substring, regardless of case:

NSString *string = @"Hello, WORLD!";
NSString *substring = @"world";
NSString *newString = [string stringByReplacingOccurrencesOfString:substring withString:@"" options:NSCaseInsensitiveSearch range:NSMakeRange(0, string.length)];
NSLog(@"%@", newString);

The resulting string is "Hello, !". Note that we used the NSCaseInsensitiveSearch option to ignore case during the search. We also specified a range to limit the search to the entire string using the NSMakeRange function.