CODEWITHSUNDEEP
sortingxsltparent-childxslt-2.0
rwolters3
rwolters3

Reputation: 73

XSLT: Sort so parent precedes child in list

I have a single flat list of "users" with parent-child relationships to other "users". A user's "parent" is the approverID. I need to sort this list so that no children ever precede their parents in the list, can use XSLT 2.0. Example input xml: 

<userList>
    <user>
        <userID>4</userID>
        <approverID>2</approverID>
    </user>
    <user>
        <userID>5</userID>
        <approverID>2</approverID>
    </user>
    <user>
        <userID>3</userID>
        <approverID>1</approverID>
    </user>
    <user>
        <userID>2</userID>
        <approverID>1</approverID>
    </user>
    <user>
        <userID>1</userID>
        <approverID>10</approverID>
    </user>
    <user>
        <userID>6</userID>
        <approverID>7</approverID>
    </user>
    <user>
        <userID>7</userID>
        <approverID>10</approverID>
    </user>
</userList>

Would have a parent child structure like (not sure best way to show it)
1 { 2 {4,5} , 3}
7 {6 }

And output XML could look something like 

<userList>
    <user>
        <userID>1</userID>
        <approverID>10</userID>
    </user>
    <user>
        <userID>2</userID>
        <approverID>1</approverID>
    </user>
    <user>
        <userID>3</userID>
        <approverID>1</approverID>
    </user>
    <user>
        <userID>4</userID>
        <approverID>2</approverID>
    </user>
    <user>
        <userID>5</userID>
        <approverID>2</approverID>
    </user>
    <user>
        <userID>7</userID>
        <approverID>10</approverID>
    </user>
    <user>
        <userID>6</userID>
        <approverID>7</approverID>
    </user>
</userList>

The only requirement is that a child user never comes before the parent, but other than that it can be sorted anyway. I feel I could do this recursively, but I know that's not the best option in a functional programming language like XSLT.

Upvotes: 1

Views: 148

Answers (1)

JLRishe
JLRishe

Reputation: 101748

There seem to be some inconsistencies between your input and output (and I think your output violates your requirements in two places), but I think this is what you are going for:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes" omit-xml-declaration="yes" />
  <xsl:key name="kUserByApprover" match="user" use="approverID"/>
  <xsl:key name="kUserById" match="user" use="userID"/>

  <xsl:template match="@* | node()" name="copy">
    <xsl:copy>
      <xsl:apply-templates select="@* | node()"/>
    </xsl:copy>
  </xsl:template>

  <xsl:template match="userList">
    <xsl:copy>
      <!-- Process users whose approver is not present -->
      <xsl:apply-templates select="user[not(key('kUserById', approverID))]" />
    </xsl:copy>
  </xsl:template>

  <xsl:template match="user">
    <xsl:call-template name="copy" />
    <!-- Process child users -->
    <xsl:apply-templates select="key('kUserByApprover', userID)" />
  </xsl:template>
</xsl:stylesheet>

When run on your sample input, the result is:

<userList>
  <user>
    <userID>1</userID>
    <approverID>10</approverID>
  </user>
  <user>
    <userID>3</userID>
    <approverID>1</approverID>
  </user>
  <user>
    <userID>2</userID>
    <approverID>1</approverID>
  </user>
  <user>
    <userID>4</userID>
    <approverID>2</approverID>
  </user>
  <user>
    <userID>5</userID>
    <approverID>2</approverID>
  </user>
  <user>
    <userID>7</userID>
    <approverID>10</approverID>
  </user>
  <user>
    <userID>6</userID>
    <approverID>7</approverID>
  </user>
</userList>

Upvotes: 1

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