NSXML不解析条目的值

Question

我有一个正在构建的iPhone应用程序，它获取一个xml文件，然后解析其中的数据以创建对象。但是，出于某种奇怪的原因，我试图解析出的文本的值总是为nil。

/*
 Sample entry
 <course> 
 <name>Afton Alps Golf Course</name> 
 <address>6600 Peller Ave S, Hastings, MN 55033</address> 
 <desc>This is only a test</desc> 
 <rating>69</rating> 
 <location>42.12452 -90.53 </location>
 <course>
*/
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName
  namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
    attributes:(NSDictionary *)attributeDict {
  if(nil != qName) {
    elementName = qName; // swap for the qName if we have a name space
  }

  if ([elementName isEqualToString:@"course"]) {
    self.currentCourse = [[[Course alloc] init] autorelease];
  } else {
      self.propertyValue = nil;
  }
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {
  if(nil != self.propertyValue) {
    [self.propertyValue appendString:string];
  }
}
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName
  namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {     
  if (qName) {
    elementName = qName; // switch for the qName
  }
  if ([elementName isEqualToString:@"name"]) {
      self.currentCourse.name = self.propertyValue;
  } else if ([elementName isEqualToString:@"address"]) {
      self.currentCourse.address = self.propertyValue;
  } else if ([elementName isEqualToString:@"desc"]) {
      self.currentCourse.description = self.propertyValue;
  } else if ([elementName isEqualToString:@"rating"]) {
      NSNumberFormatter * f = [[NSNumberFormatter alloc] init];
      [f setNumberStyle:NSNumberFormatterDecimalStyle];
      self.currentCourse.rating = [f numberFromString: self.propertyValue];
      [f release];
  } else if ([elementName isEqualToString:@"location"]) {
      NSArray *comp = [self.propertyValue componentsSeparatedByString:@" "];
      NSLog( @"%s", [comp objectAtIndex:0]);
      NSLog( @"%s", [comp objectAtIndex:1]);
      NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
      NSNumber *latitude = [formatter numberFromString:[comp objectAtIndex:0]];
      NSNumber *longitude = [formatter numberFromString:[comp objectAtIndex:1]];
      [formatter release];
      CLLocation *location = [[CLLocation alloc] initWithLatitude:latitude.floatValue
                                                        longitude:longitude.floatValue];
      self.currentCourse.location = location;
      [location release];
  } else if([elementName isEqualToString:@"course"]) {
      NSLog(@"We're done");
      [(id)[self delegate] performSelectorOnMainThread:@selector(addCourse:)
                                            withObject:self.currentCourse
                                         waitUntilDone:NO];
  }

}

**

Answer 1

看看data recieved回调中的代码：

if(nil != self.propertyValue) {
    [self.propertyValue appendString:string];
}

您从来没有设置过propertyValue anywhere (我以为它会在startElement方法中设置，但事实并非如此)，所以您永远不会追加数据。

Answer 2

每次启动一个元素时，都会将propertyValue设置为零。当您找到字符时，self.propertyValue为空。

请在您的parser:foundCharacters:消息中尝试以下内容：

    if( self.propertyValue == nil )
    {
        self.propertyValue = [NSString stringWithString:string];
    }