Number of Occurrences of a Character in NSString -- ios sdk

NSString *firstString = @"vijayadhikari";  NSScanner *scanner = [NSScanner scannerWithString: firstString]; NSCharacterSet *countChar = @"a" NSString *charactersFromString; if (!([scanner scanCharactersFromSet:countChar intoString:&charactersFromString])) {     NSLog(@"characters not  found"); } NSInteger characterCount = [charactersFromString length];  // should return 3 for this example