GDataXML nodesForXPath on Node contains items of entire GDataXMLDocument

问题

I am trying to create an iOS app which (besides a few other things) needs to load in the content of a Wordpress-Page

When I use the getPosts feature from Wordpress's XML-RPC feature, I get the following returned:

<?xml version="1.0" encoding="UTF-8"?>
<methodResponse>
  <params>
    <param>
      <value>
      <array><data>
  <value><struct>
  <member><name>post_id</name><value><string>23</string></value></member>
  <member><name>post_title</name><value><string>&lt;!--:de--&gt;Post1&lt;!--:--&gt;&lt;!--:en--&gt;Post1&lt;!--:--&gt;</string></value></member>
  <member><name>post_date</name><value><dateTime.iso8601>20140211T14:26:39</dateTime.iso8601></value></member>
  <member><name>post_date_gmt</name><value><dateTime.iso8601>20140211T12:26:39</dateTime.iso8601></value></member>
  <member><name>post_modified</name><value><dateTime.iso8601>20140217T22:32:45</dateTime.iso8601></value></member>
  <member><name>post_modified_gmt</name><value><dateTime.iso8601>20140217T20:32:45</dateTime.iso8601></value></member>
  <member><name>post_status</name><value><string>publish</string></value></member>
  <member><name>post_type</name><value><string>post</string></value></member>
  <member><name>post_name</name><value><string>im-notfall</string></value></member>
  <member><name>post_author</name><value><string>1</string></value></member>
  <member><name>post_password</name><value><string></string></value></member>
  <member><name>post_excerpt</name><value><string></string></value></member>
  <member><name>post_content</name><value><string>&lt;!--:de--&gt;&lt;b&gt;Post1&lt;/b&gt;&lt;!--:--&gt;&lt;!--:en--&gt;&lt;b&gt;Post1&lt;/b&gt;&lt;!--:--&gt;</string></value></member>
  <member><name>post_parent</name><value><string>0</string></value></member>
  <member><name>post_mime_type</name><value><string></string></value></member>
  <member><name>link</name><value><string>http://example.com/ExampleProjekt/?p=23</string></value></member>
  <member><name>guid</name><value><string>http://example.com/ExampleProjekt/?p=23</string></value></member>
  <member><name>menu_order</name><value><int>5</int></value></member>
  <member><name>comment_status</name><value><string>closed</string></value></member>
  <member><name>ping_status</name><value><string>open</string></value></member>
  <member><name>sticky</name><value><boolean>0</boolean></value></member>
  <member><name>post_thumbnail</name><value><array><data>
</data></array></value></member>
  <member><name>post_format</name><value><string>standard</string></value></member>
  <member><name>terms</name><value><array><data>
  <value><struct>
  <member><name>term_id</name><value><string>1</string></value></member>
  <member><name>name</name><value><string>Allgemein</string></value></member>
  <member><name>slug</name><value><string>allgemein</string></value></member>
  <member><name>term_group</name><value><string>0</string></value></member>
  <member><name>term_taxonomy_id</name><value><string>1</string></value></member>
  <member><name>taxonomy</name><value><string>category</string></value></member>
  <member><name>description</name><value><string></string></value></member>
  <member><name>parent</name><value><string>0</string></value></member>
  <member><name>count</name><value><int>3</int></value></member>
</struct></value>
</data></array></value></member>
  <member><name>custom_fields</name><value><array><data>
</data></array></value></member>
</struct></value>
  <value><struct>
  <member><name>post_id</name><value><string>9</string></value></member>
  <member><name>post_title</name><value><string>&lt;!--:de--&gt;Post2&lt;!--:--&gt;&lt;!--:en--&gt;Post2&lt;!--:--&gt;</string></value></member>
  <member><name>post_date</name><value><dateTime.iso8601>20140206T13:16:56</dateTime.iso8601></value></member>
  <member><name>post_date_gmt</name><value><dateTime.iso8601>20140206T11:16:56</dateTime.iso8601></value></member>
  <member><name>post_modified</name><value><dateTime.iso8601>20140217T22:33:01</dateTime.iso8601></value></member>
  <member><name>post_modified_gmt</name><value><dateTime.iso8601>20140217T20:33:01</dateTime.iso8601></value></member>
  <member><name>post_status</name><value><string>publish</string></value></member>
  <member><name>post_type</name><value><string>post</string></value></member>
  <member><name>post_name</name><value><string>neuer-erster-beitrag</string></value></member>
  <member><name>post_author</name><value><string>1</string></value></member>
  <member><name>post_password</name><value><string></string></value></member>
  <member><name>post_excerpt</name><value><string></string></value></member>
  <member><name>post_content</name><value><string>&lt;!--:de--&gt;&lt;b&gt;Post2&lt;/b&gt;&lt;!--:--&gt;&lt;!--:en--&gt;&lt;b&gt;Post2&lt;/b&gt;&lt;!--:--&gt;</string></value></member>
  <member><name>post_parent</name><value><string>0</string></value></member>
  <member><name>post_mime_type</name><value><string></string></value></member>
  <member><name>link</name><value><string>http://example.com/ExampleProjekt/?p=9</string></value></member>
  <member><name>guid</name><value><string>http://example.com/ExampleProjekt/?p=9</string></value></member>
  <member><name>menu_order</name><value><int>3</int></value></member>
  <member><name>comment_status</name><value><string>closed</string></value></member>
  <member><name>ping_status</name><value><string>open</string></value></member>
  <member><name>sticky</name><value><boolean>0</boolean></value></member>
  <member><name>post_thumbnail</name><value><array><data>
</data></array></value></member>
  <member><name>post_format</name><value><string>standard</string></value></member>
  <member><name>terms</name><value><array><data>
  <value><struct>
  <member><name>term_id</name><value><string>1</string></value></member>
  <member><name>name</name><value><string>Allgemein</string></value></member>
  <member><name>slug</name><value><string>allgemein</string></value></member>
  <member><name>term_group</name><value><string>0</string></value></member>
  <member><name>term_taxonomy_id</name><value><string>1</string></value></member>
  <member><name>taxonomy</name><value><string>category</string></value></member>
  <member><name>description</name><value><string></string></value></member>
  <member><name>parent</name><value><string>0</string></value></member>
  <member><name>count</name><value><int>3</int></value></member>
</struct></value>
</data></array></value></member>
  <member><name>custom_fields</name><value><array><data>
</data></array></value></member>
</struct></value>
  <value><struct>
  <member><name>post_id</name><value><string>5</string></value></member>
  <member><name>post_title</name><value><string>&lt;!--:de--&gt;Post3&lt;!--:--&gt;&lt;!--:en--&gt;Post3&lt;!--:--&gt;</string></value></member>
  <member><name>post_date</name><value><dateTime.iso8601>20131217T17:32:09</dateTime.iso8601></value></member>
  <member><name>post_date_gmt</name><value><dateTime.iso8601>20131217T15:32:09</dateTime.iso8601></value></member>
  <member><name>post_modified</name><value><dateTime.iso8601>20140217T22:33:18</dateTime.iso8601></value></member>
  <member><name>post_modified_gmt</name><value><dateTime.iso8601>20140217T20:33:18</dateTime.iso8601></value></member>
  <member><name>post_status</name><value><string>publish</string></value></member>
  <member><name>post_type</name><value><string>post</string></value></member>
  <member><name>post_name</name><value><string>test-beitrag-2</string></value></member>
  <member><name>post_author</name><value><string>1</string></value></member>
  <member><name>post_password</name><value><string></string></value></member>
  <member><name>post_excerpt</name><value><string></string></value></member>
  <member><name>post_content</name><value><string>&lt;!--:de--&gt;&lt;b&gt;Post3&lt;/b&gt;&lt;!--:--&gt;&lt;!--:en--&gt;&lt;b&gt;Post3&lt;/b&gt;&lt;!--:--&gt;</string></value></member>
  <member><name>post_parent</name><value><string>0</string></value></member>
  <member><name>post_mime_type</name><value><string></string></value></member>
  <member><name>link</name><value><string>http://example.com/ExampleProjekt/?p=5</string></value></member>
  <member><name>guid</name><value><string>http://example.com/ExampleProjekt/?p=5</string></value></member>
  <member><name>menu_order</name><value><int>4</int></value></member>
  <member><name>comment_status</name><value><string>closed</string></value></member>
  <member><name>ping_status</name><value><string>open</string></value></member>
  <member><name>sticky</name><value><boolean>0</boolean></value></member>
  <member><name>post_thumbnail</name><value><array><data>
</data></array></value></member>
  <member><name>post_format</name><value><string>standard</string></value></member>
  <member><name>terms</name><value><array><data>
  <value><struct>
  <member><name>term_id</name><value><string>1</string></value></member>
  <member><name>name</name><value><string>Allgemein</string></value></member>
  <member><name>slug</name><value><string>allgemein</string></value></member>
  <member><name>term_group</name><value><string>0</string></value></member>
  <member><name>term_taxonomy_id</name><value><string>1</string></value></member>
  <member><name>taxonomy</name><value><string>category</string></value></member>
  <member><name>description</name><value><string></string></value></member>
  <member><name>parent</name><value><string>0</string></value></member>
  <member><name>count</name><value><int>3</int></value></member>
</struct></value>
</data></array></value></member>
  <member><name>custom_fields</name><value><array><data>
</data></array></value></member>
</struct></value>
</data></array>
      </value>
    </param>
  </params>
</methodResponse>

Now I'm trying to get a few fields I need (content, title, id, etc.) per post via the following two foreach-statements:

GDataXMLDocument *XMLdoc = [[GDataXMLDocument alloc] initWithData:XMLcontent options:0 error:nil];
NSArray *XMLofPosts = [XMLdoc  nodesForXPath:@"//methodResponse/params/param/value/array/data/value" error:nil];

for(GDataXMLNode *post in XMLofPosts){
    NSArray *postMembers = [post nodesForXPath:@"//value/struct/member" error:nil];
    for(GDataXMLElement *postMember in postMembers){
        NSString *key = [[[postMember elementsForName:@"name"] objectAtIndex:0] stringValue];
        NSString *value = [[[postMember elementsForName:@"value"] objectAtIndex:0] stringValue];
        // ...
    }
}

However I'm facing the issue, that postMembers contains ALL members in the XML Document, not just those of one "post". Am I doing something wrong or is there a way to get around this?

回答1:

With any XPath query starting with /, you tell the XPath engine to ignore the current context and start at the root instead. Using //value, you're querying for all <value/> elements from the root, no matter what context item you pass.

Using following XPath queries should return the elements you're looking for:

Finding the context. I removed the unnecessary second / in the beginning (which will slow down the evaluation of your query) and added the /struct axis step (I guess you just forget that?).
```
/methodResponse/params/param/value/array/data
```
Return all <member/>s for the current context:
```
value/struct/member
```
Alternatively you could also explicitly denote using the current context . (which I prefer, as it clearly says what I wanted the XPath expression to do) using
```
./value/struct/member
```

来源：https://stackoverflow.com/questions/22132037/gdataxml-nodesforxpath-on-node-contains-items-of-entire-gdataxmldocument

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