NSXMLParser：解析基於另一個元素的指定元素

Question

我正在解析下面的XML與NSXMLParser，但希望僅根據XML中找到的唯一元素解析某些元素和屬性，然後中止解析。

例如，我的XML看起來是這樣的：

<?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> 

我希望能夠返回game所有players只是對checksum 值基於所以，如果我通過checksumvalue1到我的方法，我想只返回在那個game節點中發現的players與唯一的校驗和。在XML中，將會有其他帶有校驗和的遊戲，但校驗和總是唯一的。

到目前爲止，我有一些基本的解析器代碼，只是從校驗和值中讀取元素和屬性，但我不知道該從哪裏去。我也想知道XPath的NSXMLNode是否更有意義。

- (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 
    } 
} 

感謝您的幫助！

Answer 1

你必須跟蹤你是否已經找到了校驗和以及你所遇到的所有玩家。您需要布爾型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 
    } 
} 

執行[parser parse];然後你就會有玩家在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>