-shouldChangeCharactersInRange gets called before text field actually changes its text, that's why you're getting old text value. To get the text after update use:

[textField2 setText:[textField1.text stringByReplacingCharactersInRange:range withString:string]];

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{    NSString * searchStr = [textField.text stringByReplacingCharactersInRange:range withString:string];    NSLog(@"%@",searchStr);    return YES;}

Swift 3

Based on the accepted answer, the following should work in Swift 3:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {    let newString = NSString(string: textField.text!).replacingCharacters(in: range, with: string)    return true}

Note

Both String and NSString have methods called replacingCharacters:inRange:withString. However, as expected, the former expects an instance of Range, while the latter expects an instance of NSRange. The textField delegate method uses an NSRange instance, thus the use of NSString in this case.