iOS textField禁止输入指定字

iOS textField禁止输入指定字母（如：禁止输入a、b、A、B）

1、定义宏

#define NUMBERS @"aAbB"

2、textfield—delegate

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

{

    NSCharacterSet * cs;

    cs = [[NSCharacterSet characterSetWithCharactersInString:NUMBERS] invertedSet];

    NSString * filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];

    BOOL basicTest = [string isEqualToString:filtered];

    if(basicTest) {

        

        return NO;

        

    }

    return YES;

}