检查 nsstring 中的多个字符

我有一个字符串，我想检查该字符串中的多个字符，下面的代码我对一个字符工作正常，如何检查多个字符。

NSString *yourString = @"ABCCDEDRFFED"; // For example
NSScanner *scanner = [NSScanner scannerWithString:yourString];

NSCharacterSet *charactersToCount = @"C" // For example
NSString *charactersFromString;

if (!([scanner scanCharactersFromSet:charactersToCount intoString:&charactersFromString])) {
    // No characters found
    NSLog(@"No characters found");
}

NSInteger characterCount = [charactersFromString length];

UPDATE:前面的例子被打破了，因为NSScanner不应该这样使用。这是一个更直接的例子：

NSString* string = @"ABCCDEDRFFED";
NSCharacterSet* characters = [NSCharacterSet characterSetWithCharactersInString:@"ABC"];
NSUInteger characterCount;

NSUInteger i;
for (i = 0; i < [yourString length]; i++) {
  unichar character = [yourString characterAtIndex:i];
  if ([characters characterIsMember:character]) characterCount++;
}

NSLog(@"Total characters = %d", characterCount);