How to get first four letters from string in Swift 3?

Question

I am trying to do IFSCCode validation in swift, but the problem I'm facing is I am not able to fetch the first four letters in string.

IFSC Code example:

ABCD0200000

This is how an IFSC Code looks:

1. First four characters in IFSC Code are always alphabets
2. Fifth character is always a zero.
3. And rest can be anything
4. The length of IFSC Code should not be greater than or less than 11. It should 11 in length.

I have written code for ifs code validation in Objective C, but I am not that familiar in Swift so getting a problem in replicating the same in Swift.

The following is the code which I have written in Objective C:

- (BOOL)validateIFSCCode:(NSString*)ifsccode {   if (ifsccode.length < 4) {     return FALSE;   }   for (int i = 0; i < 4; i++) {     if (![[NSCharacterSet letterCharacterSet]             characterIsMember:[ifsccode characterAtIndex:i]]) {       return FALSE;     }   }   if (ifsccode.length < 10) {     return FALSE;   }   if ([ifsccode characterAtIndex:4] != '0') {     return FALSE;   } else {     return TRUE;   } } 

In Swift 3

func validateIfscCode(_ ifscCode : String) -> Bool{     if(ifscCode.characters.count < 4){         return false;     }      for( _ in 0 ..< 4){         let charEntered = (ifscCode as NSString).character(at: i)     }     if(ifscCode.characters.count < 10){         return false;     }      let idx = ifscCode[ifscCode.index(ifscCode.startIndex, offsetBy: 4)]      print("idx:%d",idx)     if (idx == "0"){     }     return true } 

Answer 1

The easiest way to get a string's prefix is with

// Swift 3 String(string.characters.prefix(4))  // Swift 4 and up string.prefix(4)  // Objective-C NSString *firstFour = [string substringToIndex:4];