NSXMLParser：解析基于另一个元素的指定元素

Question

我正在解析下面的XML与NSXMLParser，但希望仅根据XML中找到的唯一元素解析某些元素和属性，然后中止解析。

例如，我的XML看起来是这样的：

<?xml version="1.0" encoding="UTF-8"?> 
<systems> 
<system id="system1"> 
    <game title="game1"> 
     <checksums> 
      <checksum value="checksumvalue1" /> 
     </checksums> 
     <players> 
      <player name="name1" description="description1" /> 
      <player name="name2" description="description2" /> 
     </players> 
    </game> 
</system> 

我希望能够返回game所有players只是对checksum 值基于所以，如果我通过checksumvalue1到我的方法，我想只返回在那个game节点中发现的players与唯一的校验和。在XML中，将会有其他带有校验和的游戏，但校验和总是唯一的。

到目前为止，我有一些基本的解析器代码，只是从校验和值中读取元素和属性，但我不知道该从哪里去。我也想知道XPath的NSXMLNode是否更有意义。

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict{ 

if ([elementName isEqualToString:@"checksum"] && [[attributeDict valueForKey:@"value"] isEqualToString:@"checksumvalue1"]) { 
    NSString *checksumValue = [attributeDict valueForKey:@"value"]; 
    NSLog(@"value: %@", checksumValue); 

// print players in only one game node that contains the unique checksum value 
    } 
} 

感谢您的帮助！

Answer 1

你必须跟踪你是否已经找到了校验和以及你所遇到的所有玩家。您需要布尔型foundGameChecksum和NSMutableArray* players。不要忘了players = [[NSMutableArray alloc] init];

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict{ 

    if ([elementName isEqualToString:@"checksum"] && [[attributeDict valueForKey:@"value"] isEqualToString:@"checksumvalue1"]) { 
     NSString *checksumValue = [attributeDict valueForKey:@"value"]; 
     NSLog(@"value: %@", checksumValue); 

     foundGameChecksum = YES; 
     // print players in only one game node that contains the unique checksum value 
    } else if(foundGameChecksum && [elementName isEqualToString:@"player"]) { 
     [players addObject:[attributeDict valueForKey:@"name"]]; 
    } 
} 

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName 
{ 
    if(foundGameChecksum && [elementName isEqualToString:@"players"]) { 
     [parser abortParsing]; // Stop parsing 
    } 
} 

执行[parser parse];然后你就会有玩家在players

即：

<?xml version="1.0" encoding="UTF-8"?> 
<systems> 
    <system id="system1"> 
     <game title="game1"> 
      <checksums> 
       <checksum value="checksumvalue1" /> <!-- Found. Start adding --> 
      </checksums> 
      <players> 
       <player name="name1" description="description1" /> <!-- Add --> 
       <player name="name2" description="description2" /> <!-- Add --> 
      </players> <!-- Stop adding --> 
     </game> 
    </system> 
</systems>