Macro expansion

To demonstrate macros in the XML, we'll show XML with macro definitions and XML with the macros expanded. We'll also show the XML with macros as a property = value output, which may be easier on the eyes;

A macro is identified by a prefix "${" and suffix "}" with the string values between being the macro name. The macro name must exist in the XML file at a point above the macro's use. Macros expand as either values (a string) or they will expand as an element (object).

In the example, note the following value expansions:

<foo_bar> has a value that is simply two macro values expanded independently, ${foo}${bar}.
<nested_join_result> is similar to <foo_bar>, but the two values are inside another macro definition. For this, the inner macros are expanded, then the outer macro is expanded.

and note the following element expansion:

<obj_lkup> is a macro that will expand into the element <lkup_a_obj> which has two values: aa and bb. What is important to take away here is the key <obj_lkup> remains and the expanded element's children, aa and bb, are copied inside key <obj_lkup> as child elements, while the key of the actual value, <lkup_a_obj>, is not part of the expansion.

Macro expansion XML Examples

XML with macros

<a_configs>
          <foo>topfoo</foo>
          <bar>topbar</bar>
          <foo_bar>the ${foo}${bar} value</foo_bar>
          <lkup_outer_inner_value>the outer inner value</lkup_outer_inner_value>
          <nested_outer>outer</nested_outer>
          <nested_inner>inner</nested_inner>
          <nested_join_result>${lkup_${nested_outer}_${nested_inner}_value}</nested_join_result>
          <lkup_a_obj>
               <aa>aa value</aa>
               <bb>bb value</bb>
          </lkup_a_obj>
          <obj_lkup>${lkup_a_obj}</obj_lkup>
          <lkup_aa_obj>
               <foo>foo</foo>
               <bar>bar</bar>
               <foo_bar>the ${foo}${bar} value</foo_bar>
          </lkup_aa_obj>
          <obj_aalkup>${lkup_aa_obj}</obj_aalkup>
          <deep>
               <deeper>
                    <deep_aalkup>${lkup_aa_obj}</deep_aalkup>
               </deeper>
          </deep>
</a_configs>

XML with macros printed as a property list

a_configs =  {
          foo = topfoo;
          bar = topbar;
          foo_bar = the ${foo}${bar} value;
          lkup_outer_inner_value = the outer inner value;
          nested_outer = outer;
          nested_inner = inner;
          nested_join_result = ${lkup_${nested_outer}_${nested_inner}_value};
          lkup_a_obj =  {
               aa = aa value;
               bb = bb value;
          };
          obj_lkup = ${lkup_a_obj};
          lkup_aa_obj =  {
               foo = foo;
               bar = bar;
               foo_bar = the ${foo}${bar} value;
          };
          obj_aalkup = ${lkup_aa_obj};
          deep =  {
               deeper =  {
                    deep_aalkup = ${lkup_aa_obj};
               };
          };
     };

XML with all macros expanded to values

<a_configs>
     <foo>topfoo</foo>
     <bar>topbar</bar>
     <foo_bar>the topfootopbar value</foo_bar>
     <lkup_outer_inner_value>the outer inner value</lkup_outer_inner_value>
     <nested_outer>outer</nested_outer>
     <nested_inner>inner</nested_inner>
     <nested_join_result>the outer inner value</nested_join_result>
     <lkup_a_obj>
          <aa>aa value</aa>
          <bb>bb value</bb>
     </lkup_a_obj>
     <obj_lkup>
          <aa>aa value</aa>
          <bb>bb value</bb>
     </obj_lkup>
     <lkup_aa_obj>
          <foo>foo</foo>
          <bar>bar</bar>
          <foo_bar>the foobar value</foo_bar>
     </lkup_aa_obj>
     <obj_aalkup>
          <foo>foo</foo>
          <bar>bar</bar>
          <foo_bar>the foobar value</foo_bar>
     </obj_aalkup>
     <deep>
          <deeper>
               <deep_aalkup>
                    <foo>foo</foo>
                    <bar>bar</bar>
                    <foo_bar>the foobar value</foo_bar>
               </deep_aalkup>
          </deeper>
     </deep>
</a_configs>