Loading and parsing external XML files

XML is a common data exchange format; it is useful to be able to parse (process the contents of) text files and strings containing data in this format. C# offers a range of classes and methods to make such processing straightforward.

Getting ready

You'll find player name and score data in XML format in the playerScoreData.xml file in the 0423_08_04 folder. The contents of this file are as follows:

<scoreRecordList>
    <scoreRecord>
        <player>matt</player>
        <score>2200</score>
        <date>
            <day>1</day>
            <month>Sep</month>
            <year>2012</year>
        </date>
    </scoreRecord>

    <scoreRecord>
        <player>jane</player>
        <score>500</score>
        <date>
            <day>12</day>
            <month>May</month>
            <year>2012</year>
        </date>
    </scoreRecord>
</scoreRecordList>

The data is structured by a root element named scoreRecordList, which contains a sequence of scoreRecord elements. Each scoreRecord element contains a player element (which contains a player's name), a score element (which has the integer content of the player's score), and a date element, which itself contains three child elements, day, month, and year.

How to do it...

To load and parse external XML files, follow these steps:

  1. Add the following C# script to Main Camera:
    // file: ParseXML.cs
using UnityEngine;
using System.Collections;

using System.Xml;
using System.IO;

public class ParseXML : MonoBehaviour {
    public TextAsset scoreDataTextFile;

    private void Start() {
        string textData = scoreDataTextFile.text;
        ParseScoreXML( textData );
    }

    private void ParseScoreXML(string xmlData) {
        XmlDocument xmlDoc = new XmlDocument();
        xmlDoc.Load( new StringReader(xmlData) );

        string xmlPathPattern = "//scoreRecordList/scoreRecord";
        XmlNodeList myNodeList = xmlDoc.SelectNodes( xmlPathPattern );

        foreach(XmlNode node in myNodeList)
            print ( ScoreRecordString( node ) );

    }

    private string ScoreRecordString(XmlNode node) {
        XmlNode playerNode = node.FirstChild;
        XmlNode scoreNode = playerNode.NextSibling;
        XmlNode dateNode = scoreNode.NextSibling;

        return "Player = " + playerNode.InnerXml + ", score = " + scoreNode.InnerXml + ", date = " + DateString( dateNode );
    }

    private string DateString(XmlNode dateNode) {
        XmlNode dayNode = dateNode.FirstChild;
        XmlNode monthNode = dayNode.NextSibling;
        XmlNode yearNode = monthNode.NextSibling;

        return dayNode.InnerXml + "/" + monthNode.InnerXml + "/" + yearNode.InnerXml;
    }
}
  2. Import the playerScoreData.xml file into your project.
  3. Select the Main Camera and set playerScoreData.xml as the Score Data Text File variable for the Parse XML component.
  4. The output of the print() statements should be visible in the Console window:
    How to do it...

How it works...

Note the need to use the System.Xml and System.IO packages for this recipe.

The text property of the TextAsset variable scoreDataTextFile provides the contents of the XML file as a string, which is passed to the ParseScoreXML()method. This method creates a new XmlDocument variable with the contents of this string. The XmlDocument class provides the SelectNodes() method, which returns a list of node objects for a given element path. In this example, a list of scoreRecord nodes is requested. A for-each statement prints out the string returned by the ScoreRecordString() method when each node object is passed to it.

The ScoreRecordString() method relies on the ordering of the XML elements to retrieve the player's name and score, and it gets the date as a slash-separated string by passing the node containing the three date components to the DateString() method.

There's more...

Some details you don't want to miss:

Retrieving XML data files from the web

You can use the WWW Unity class if the XML file is located on the Web rather than in your Unity project.

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