使用 NSXMLParser initWithStream：未收到解析器委托方法

我正在解决的基本问题是使用NSStream用于解析传入的增量 XML 数据的类。数据从来都不是完整的 XML 文档，但我希望根据套接字可以读取的数据量以增量块的形式接收和处理它。

查看文档NSXMLParser，看起来像initWithStream:方法来初始化一个NSXMLParser将是我的问题的完美解决方案。我可以用一个初始化解析器NSInputStream然后调用parse方法上NSXMLParser每当我通过套接字接收数据时，该数据应该依次调用NSXMLParser代表们。

但是，我没有看到任何委托被调用，我看到被调用的唯一方法是流委托stream:handleEvent:。 Apple 或其他开发人员似乎很少甚至没有此 API 的示例。关于我做错了什么或如何使用的任何想法initWithStream:正确吗？

内容解析器.h

@interface ContentParser : NSObject <NSStreamDelegate, 
                                     NSXMLParserDelegate>
{
   NSInputStream *inputStream;
   NSOutputStream *outputStream;
   NSMutableData *receivedData;
   NSXMLParser *xmlParser;
}
- (void)initStream;

内容解析器.m

@implementation ContentParser

- (void)initStream
{    
   CFReadStreamRef readStream;
   CFWriteStreamRef writeStream;

   CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault, 
                                     (CFStringRef)@"<hostname>", 
                                     <port>, 
                                     &readStream, 
                                     &writeStream);

   inputStream = (__bridge NSInputStream *)readStream;
   outputStream = (__bridge NSOutputStream *)writeStream;

   inputStream.delegate = self;
   outputStream.delegate = self;

   [inputStream  scheduleInRunLoop:[NSRunLoop currentRunLoop]
                           forMode:NSDefaultRunLoopMode];
   [outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] 
                           forMode:NSDefaultRunLoopMode];

   [inputStream open];
   [outputStream open];

   xmlParser = [[NSXMLParser alloc] initWithStream:inputStream];
   [xmlParser setDelegate:self];
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName 
                                        namespaceURI:(NSString *)namespaceURI 
                                       qualifiedName:(NSString *)qName 
                                          attributes:(NSDictionary *)attributeDict
{
   NSLog(@"didStartElement: %@, attributeDict: %@", elementName, attributeDict);
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
   NSLog(@"foundCharacters: %@", string);
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName 
                                      namespaceURI:(NSString *)namespaceURI 
                                     qualifiedName:(NSString *)qName
{
   NSLog(@"didEndElement: %@", elementName);
}

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError
{
   NSLog(@"Error %ld, Description: %@, Line: %ld, Column: %ld", 
      [parseError code], [[parser parserError] localizedDescription], 
      [parser lineNumber], [parser columnNumber]);
}


- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)eventCode
{
   switch (eventCode) {
       case NSStreamEventHasBytesAvailable:
       {
           if (stream == inputStream) {
               NSInputStream *is = (NSInputStream *)stream;
               if (receivedData == nil) {
                   receivedData = [[NSMutableData alloc] init];
               }

               uint8_t buf[1024];
               NSInteger bytesRead = [is read:buf maxLength:1024];
               if (bytesRead == -1) {
                  NSLog(@"Network read error");
               } else if (bytesRead == 0) {
                  NSLog(@"No buffer received");
               } else {
                  [receivedData appendBytes:buf length:bytesRead];
                  BOOL parserResult = [xmlParser parse];
                  if (parserResult == NO) {
                     NSLog(@"Unable to parse XML");
                  }
               }
           }
           break;
       }
       default:
          break;
    }
}

@end

我弄清楚了问题是什么，并在这里回答它，以防其他人将来遇到这个问题+[NSXMLParser initWithStream]那里没有很多文档。

我需要打电话-[NSXMLParser parse]在我分配之后NSXMLParser并指定我自己为代表。但因为它是一个同步函数，所以我需要在另一个线程中调用它，这样我就不会阻塞当前线程并且它可以接收NSStream事件。我也不需要让自己成为代表NSInputStream.

使用 Grand Central Dispatch (GCD) 可以非常简单地完成此操作，如下所示：

// alloc and init the xml parser
xmlParser = [[NSXMLParser alloc] initWithStream:inputStream];
[xmlParser setDelegate:self];

// block to execute
dispatch_block_t dispatch_block = ^(void)
{
    [xmlParser parse];
};

// create a queue with a unique name
dispatch_queue_t dispatch_queue = dispatch_queue_create("parser.queue", NULL);

// dispatch queue
dispatch_async(dispatch_queue, dispatch_block);

// cleanup
dispatch_release(dispatch_queue);

这是完整的工作示例，以防万一有人无法理解我上面发布的内容。

内容解析器.h

@interface ContentParser : NSObject <NSStreamDelegate, 
                                     NSXMLParserDelegate>
{
   NSInputStream *inputStream;
   NSOutputStream *outputStream;
   NSMutableData *receivedData;
   NSXMLParser *xmlParser;
}
- (void)initStream;

内容解析器.m

@implementation ContentParser

- (void)initStream
{    
   CFReadStreamRef readStream;
   CFWriteStreamRef writeStream;

   CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault, 
                                     (CFStringRef)@"<hostname>", 
                                     <port>, 
                                     &readStream, 
                                     &writeStream);

   inputStream = (__bridge NSInputStream *)readStream;
   outputStream = (__bridge NSOutputStream *)writeStream;

   outputStream.delegate = self;

   [inputStream  scheduleInRunLoop:[NSRunLoop currentRunLoop]
                           forMode:NSDefaultRunLoopMode];
   [outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] 
                           forMode:NSDefaultRunLoopMode];

   [inputStream open];
   [outputStream open];

   xmlParser = [[NSXMLParser alloc] initWithStream:inputStream];
   [xmlParser setDelegate:self];

   dispatch_block_t dispatch_block = ^(void)
   {
      [xmlParser parse];
   };
   dispatch_queue_t dispatch_queue = dispatch_queue_create("parser.queue", NULL);
   dispatch_async(dispatch_queue, dispatch_block);
   dispatch_release(dispatch_queue);
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName 
                                        namespaceURI:(NSString *)namespaceURI 
                                       qualifiedName:(NSString *)qName 
                                      attributes:(NSDictionary *)attributeDict
{
   dispatch_block_t dispatch_block = ^(void)
   {
      NSLog(@"didStartElement: %@, attributeDict: %@", 
         elementName, attributeDict);
   };
   dispatch_queue_t main_queue = dispatch_get_main_queue();
   dispatch_async(main_queue, dispatch_block);
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
   dispatch_block_t dispatch_block = ^(void)
   {
      NSLog(@"foundCharacters: %@", string);
   };
   dispatch_queue_t main_queue = dispatch_get_main_queue();
   dispatch_async(main_queue, dispatch_block);
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName 
                                      namespaceURI:(NSString *)namespaceURI 
                                     qualifiedName:(NSString *)qName
{
   dispatch_block_t dispatch_block = ^(void)
   {
      NSLog(@"didEndElement: %@", elementName);
   };
   dispatch_queue_t main_queue = dispatch_get_main_queue();
   dispatch_async(main_queue, dispatch_block);
}

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError
{
   dispatch_block_t dispatch_block = ^(void)
   {
      NSLog(@"Error %ld, Description: %@, Line: %ld, Column: %ld", 
         [parseError code], [[parser parserError] localizedDescription], 
         [parser lineNumber], [parser columnNumber]);
   };
   dispatch_queue_t main_queue = dispatch_get_main_queue();
   dispatch_async(main_queue, dispatch_block);
}   

- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)eventCode
{
   switch (eventCode) {
      case NSStreamEventHasSpaceAvailable:
      {
         /* write bytes to socket */
         break;
      }
      default:
         break;
    }
}

@end