GHPopupEditView *popupView = [[GHPopupEditView alloc] init];
[popupView setTitle:@"edit nickname"];
[popupView setPlaceholderString:@"Please enter a nickname"];
[popupView setKeyboardType:UIKeyboardTypeDefault];
[popupView setOKButtonThemeColor:[UIColor orangeColor]];
[popupView setShouldChangeHandler:^(UITextField *textField, NSRange range, NSString *replacementString) {
    if (range.length == 0) { // add
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", @"[\\w_]+"];
        return [predicate evaluateWithObject:replacementString];
    }
    return YES;
}];
[popupView setVerifyHandler:^(NSString *text) {
    NSString *nickname = [text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
    if (nickname.length == 0) {
        return @"Nickname can not be empty.";
    }
    return @"";
}];
[popupView setCompletionHandler:^(NSString *text) {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:[NSString stringWithFormat:@"hello %@.", text] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
    [alert show];
}];
[popupView show];