初始化银行卡卡号

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

NSString *text = [textField text];

NSCharacterSet *characterSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789\b"];

string = [string stringByReplacingOccurrencesOfString:@" " withString:@""];

if ([string rangeOfCharacterFromSet:[characterSet invertedSet]].location != NSNotFound) {

return NO;

}

text = [text stringByReplacingCharactersInRange:range withString:string];

text = [text stringByReplacingOccurrencesOfString:@" " withString:@""];

NSString *newString = @"";

while (text.length > 0) {

NSString *subString = [text substringToIndex:MIN(text.length, 4)];

newString = [newString stringByAppendingString:subString];

if (subString.length == 4) {

newString = [newString stringByAppendingString:@" "];

}

text = [text substringFromIndex:MIN(text.length, 4)];

}

newString = [newString stringByTrimmingCharactersInSet:[characterSet invertedSet]];

if (newString.length >= 25) {

return NO;

}

[textField setText:newString];

return NO;

}