Parsing XML documents iOS - ios

Question

I have to parse this document and I plan on using NSXMLparser but the only problem is I do not know how to get the information I want. I don't know how to navigate through each tag, I have seen simple examples but when I try to use their method I get random tags and information I don't want. Can someone explain how to get certain information from a complex XML structure such as this one?
Thanks!
<kml xmlns:ns3="urn:oasis:names:tc:ciq:xsdschema:xAL:2.0" xmlns:ns2="http://www.w3.org/2005/Atom"
xmlns="http://www.opengis.net/kml/2.2">
<Document>
<description>Available CAR2GO Vehicles</description>
<Style id="car2go">
<IconStyle>
<Icon>
<href>http://www.car2go.com/common/images/openapi/marker_car2go.png
</href>
</Icon>
<hotSpot y="0.0" x="0.0" />
</IconStyle>
</Style>
<Style id="car2go_ed">
<IconStyle>
<Icon>
<href>http://www.car2go.com/common/images/openapi/marker_car2go_ed.png
</href>
</Icon>
<hotSpot y="0.0" x="0.0" />
</IconStyle>
</Style>
<Placemark>
<name>UL-C5887</name>
<description>Sudetenweg, 89075 Ulm<br/>Fuel
24<br/>Interior GOOD<br/>Exterior GOOD
</description>
<styleUrl>#car2go_ed</styleUrl>
<ExtendedData>
<Data name="fuel">
<value>24</value>
</Data>
<Data name="interior">
<value>GOOD</value>
</Data>
<Data name="exterior">
<value>GOOD</value>
</Data>
<Data name="vin">
<value>WME4513001K154655</value>
</Data>
<Data name="engineType">
<value>ED</value>
</Data>
<Data name="charging">
<value>true</value>
</Data>
</ExtendedData>
<Point>
<coordinates>10.029,48.4362,0</coordinates>
</Point>
</Placemark>
<Placemark>
<name>UL-C5889</name>
<description>Heilmeyersteige, 89075 Ulm<br/>Fuel
58<br/>Interior GOOD<br/>Exterior GOOD
</description>
<styleUrl>#car2go</styleUrl>
<ExtendedData>
<Data name="fuel">
<value>58</value>
</Data>
<Data name="interior">
<value>GOOD</value>
</Data>
<Data name="exterior">
<value>GOOD</value>
</Data>
<Data name="vin">
<value>WME4513001K154655</value>
</Data>
<Data name="engineType">
<value>CE</value>
</Data>
</ExtendedData>
<Point>
<coordinates>9.947235,48.410497,0</coordinates>
</Point>
</Placemark>
</Document>

Answer 1

I get random tags and information I don't want
With NSXMLParser you don't navigate through the XML. Instead, you create a delegate for the parser that gets messages each time the parser encounters something -- a tag, a value, etc. Your delegate needs to watch for the tags and values that it's interested in and do whatever makes sense for your app when those arrive. So, the tags you're seeing aren't random, they're just the tags from the file you're parsing in the order in which they appear in the file.
Can someone explain how to get certain information from a complex XML structure such as this one?
Generally, your parser delegate will be a little like a state machine that keeps track of which tag it's parsing, what data it sees, etc. That may be more than you're up for, in which case you might want to look into other XML parsing options than NSXMLParser. TouchXML is one library that's popular because it parses the file for you and then lets you look through the data with Xquery.

Answer 2

I would highly suggest you do not reinvent the wheel and use a high level 3rd party library which will make your life a ton easier. #mattt of AFNetworking fame amongst others has an excellent XML parsing library called Ono.

Answer 3

I suggest you examine the strategy demonstrated by Apple's own example code here:
https://developer.apple.com/library/ios/samplecode/SeismicXML/Introduction/Intro.html#//apple_ref/doc/uid/DTS40007323
The actual parsing code is here:
https://developer.apple.com/library/ios/samplecode/SeismicXML/Listings/SeismicXML_APLParseOperation_m.html#//apple_ref/doc/uid/DTS40007323-SeismicXML_APLParseOperation_m-DontLinkElementID_11
All the work is done by the parser's delegate (which is this object, self). Notice in particular how didStartElement:... makes choices depending on what kind of element has just been encountered.
I should also mention that there is another strategy, where instead of the delegate making these choices, you keep repointing the parser at a different delegate. Here, I develop a general version of that strategy and show how to adapt it to a particular parsing situation: http://www.apeth.com/iOSBook/ch36.html#_xml