Null Support

Null Support

This document explains how to set null support in the Lucee server admin, assigning null value for a variable and how to use null and nullvalue. It is an annotation of the video found here: https://www.youtube.com/watch?v=GSlWfLR8Frs

Enabling NULL support

You can enable null support via the Lucee Server Admin --> Language/compiler and setting Null support to complete support (exclusive to Lucee) or partial support (default, same as Adobe CF).

Or via Application.cfc / <cfapplication>

this.nullSupport = true;

Explanation

Illustration 1:

<cfscript>
	function test() {
	}
	dump( test() );

<span class="nv">t</span><span class="o">=</span><span class="nf">test</span><span class="p">();</span>
<span class="nf">dump</span><span class="p">(</span><span class="nv">t</span><span class="p">);</span>
<span class="nf">dump</span><span class="p">(</span> <span class="nf">isNull</span><span class="p">(</span> <span class="nv">t</span> <span class="p">)</span> <span class="p">);</span>
<span class="nf">dump</span><span class="p">(</span> <span class="nf">isNull</span><span class="p">(</span> <span class="nv">notexisting</span> <span class="p">)</span> <span class="p">);</span>



</cfscript>

In this example, the function test() does not return a value. This, in effect, is the same as returning null. If you dump the result of the function (dump( test( ) );), you will see that the dump outputs Empty: Null.

If we assign the function result to a variable, i.e. t = test();, and reference the variable, i.e. dump( t ); an error will be thrown when using partial support for null: "the key [T] does not exist". If we enable full support, you will be able to reference the variable without error, the dump output will be Empty: Null and IsNull( t ) will evaluate true.

In all cases, dump( isNull( notexisting ) ); will throw an error.

Illustration 2:

query datasource="test" name="qry" {
	echo("select '' as empty, null as _null");
}
dump( qry );
dump( qry._null );

With partial support for NULL enabled, dump(qry._null); will output an empty string. With full support, Empty: null will be output and IsNull( qry._null ); will evaluate true.

NullValue() function and null keyword

With partial support for NULL, the NullValue() function must be used to explicitly return a null value (this will work in all scenarios). For example:

var possibleVariable = functionThatMayOrMayNotReturnNull();
return possibleVariable ?: NullValue();

With full support, you are able to use the null keyword directly and, as illustrated above, can assign it to a variable directly:

t = null;
dump( t );

See also