默认情况下，
一个简单的例程，使用NSScanner查找前导选项卡的数量，但它没有找到任何选项卡。代码转到scanCharactersFromSet语句的"else"。我尝试将asciiTabRange.location更改为0x49（ASCII"I"），并将输入字符串更改为以"I"开头，而不是以制表符开头，它会找到一个前导"I"，因此问题似乎特定于前导制表符。lldb输出显示字符串以一个tab开头，[asciiTab characterIsMember]语句返回YES。
{
self = [super init];
if (self) {
if ([recordString length] != 0) {
NSScanner* theScanner = [NSScanner scannerWithString: recordString];
NSString* testConfirmString = [theScanner string];
const char* testConfirmCStr = [testConfirmString cStringUsingEncoding: NSASCIIStringEncoding];
if (testConfirmCStr != NULL);
NSRange asciiTabRange;
asciiTabRange.location = 0x09;
asciiTabRange.length = 1;
NSCharacterSet* asciiTab = [NSCharacterSet characterSetWithRange: asciiTabRange];
if ([asciiTab characterIsMember: 0x09] == YES) {
testConfirmCStr = 0;
}
NSString* tabString = nil;
if ([theScanner scanCharactersFromSet: asciiTab
intoString: &tabString] == YES) {
tabLevel = [tabString length];
} else {
tabLevel = 0;
}
itemText = [recordString substringFromIndex: tabLevel];
} else {
// ?
}
children = [[NSMutableArray alloc] init];
}
return self;
}
（lldb）x-c 32 testConfirmCStr0x600000043a91:09 49 6e 64 75 73 74 72 79 3a 09 54 65 73 74 53.行业：.TestS0x600000043aa1:65 76 65 72 61 6c 00 00 00 00 000 00 00 00 0 00 00 00 90每年。。。。。。。。。。
NSScanner会忽略空白和换行符；空白字符集包括制表符（U+0009）。尝试删除此默认值：
NSScanner* theScanner = [NSScanner scannerWithString: recordString];
theScanner.charactersToBeSkipped = nil;
同样值得注意的是NSScanner属性scanLocation，在简单的情况下，这可能有助于计算实际的选项卡：
NSString *recordString = @"tttHellottGoodbyetHello";
NSScanner* theScanner = [NSScanner scannerWithString: recordString];
theScanner.charactersToBeSkipped = nil;
NSRange asciiTabRange;
asciiTabRange.location = 0x09;
asciiTabRange.length = 1;
NSCharacterSet* asciiTab = [NSCharacterSet characterSetWithRange: asciiTabRange];
NSString *tabString;
unsigned long indexOfFirstTabInRun = 0;
unsigned long tabsInRun = 0;
while (!theScanner.isAtEnd) {
indexOfFirstTabInRun = (unsigned long)theScanner.scanLocation;
if ([theScanner scanCharactersFromSet: asciiTab intoString: &tabString]) {
tabsInRun = (unsigned long) theScanner.scanLocation - indexOfFirstTabInRun;
NSLog(@"tabCount: %lu - starting at index %lu", tabsInRun, indexOfFirstTabInRun);
} else {
[theScanner scanCharactersFromSet:asciiTab.invertedSet intoString:nil];
}
}