Getting the value of an Element in Cocoa using Tou

问题:

I am using TouchXml because of the given limitations of NSXML on the actual iPhone. Anyway, I'm just starting out with Objective-C, I come from a C# background, and felt like learning something new..anyhow.. here is my xml file...

<?xml version="1.0" encoding="utf-8"?>
<FundInfo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://tempuri.org/webservices">
  <FundsReleaseDate>2009-02-11T00:00:00</FundsReleaseDate>
  <FundValue>7800</FundValue>
  <FundShares>1000</FundShares>
</FundInfo>

I'm trying to get 7800, i.e FundValue. Can someone point me in the correct direction, I am using the TouchXml CXMLDocument and myParser is of type CXMLDocument, I have tried

NSArray *nodes = [myParser nodesForXPath:@"//FundInfo" error:&err];

Basically nodes evaluates to nil

if ([nodes count] > 0 ) {
    amount = [nodes objectAtIndex:1];
}

UPDATE 1: I have abandoned parsing using XPath, and have replaced it with NSURLRequest, so now I have the entire XML in a string, but my rude introduction to objective-C continues...I just realized how spoiled I have become to the .NET BCL where things like Regex are so easily available.

UPDATE2: I've figured out how to use RegexKitLite for regex.

So the question now is, how do I get the "7800" from inside FundValue which is now one big string. I have confirmed I have it in my NSString by writing it using NSLog.

回答1:

The problem is that your XML has a namespace, which means your XPath does not actually match. Unfortunately there is no default mapping, and XPath does not actually define a good way to handle this internally, so you can't fix it simply by changing the XPath. Instead you need to inform the interpreter how you want to map it in your XPath.

It looks like TouchXML implements support for this via:

- (NSArray *)nodesForXPath:(NSString *)xpath namespaceMappings:(NSDictionary *)inNamespaceMappings error:(NSError **)error;

So you can try something like:

NSDictionary *mappings = [NSDictionary dictionaryWithObject:@"http://tempuri.org/webservices" forKey:@"tempuri"];
[myParser nodesForXPath:@"//tempuri:FundInfo" namespaceMappings:mappings error:&err];

回答2:

I had a similar problem. ANY selection on an XML that has a namespace specified (xmlns="http://somenamespace") will result in no nodes found. Very strange considering it does support the additional namespace formats such as xmlns:somenamespace="http://somenamespace".

In any case, by far the easiest thing to do is do a string replace and replace xmlns="http://tempuri.org/webservices with an empty string.

Overall I like touchxml, but I can't believe this bug still exists.

回答3:

Try

NSArray *nodes = [myParser nodesForXPath:@"/FundInfo/*" error:&err];