You can reference a previously defined variable to return its value. To reference a variable in Net.Data macros, specify the variable name inside $( and ). For example:
$(variableName) $(homeURL)
When Net.Data finds a variable reference, it substitutes the variable reference with the value of the variable. Variable references can contain strings, variable references, and function calls.
You can dynamically generate variable names. With this technique, you can use loops to process variably-sized tables or input data for lists that are built at run time, when the number in the list cannot be determined in advanced. For example, you can generate lists of HTML form elements that are generated based on records returned from an SQL query.
To use variables as part of your text presentation statements, reference them in the HTML blocks of your macro.
Invalid variable references: Invalid variable references are resolved to the empty string. For example, if a variable reference contains invalid characters such as an exclamation point (!), the reference is resolved to the empty string.
Valid variable names must begin with an alphanumeric character or an underscore, and they can consist of alphanumeric characters, including a period, underscore, and hash mark.
Example 1: Variable reference in a link
If you have defined the variable homeURL:
%DEFINE homeURL="http://www.ibm.com/"
You can refer to the home page as $(homeURL) and create a link:
<A href="$(homeURL)">Home page</A>
You can reference variables in many parts of the Net.Data macro; check the language constructs in this chapter to determine in which parts of the macro variable references are allowed. If the variable has not yet been defined at the time it is referenced, Net.Data returns an empty string. A variable reference alone does not define the variable.
Example 2: Dynamically generated variable references
Assume that you run an SQL SELECT statement with any number of elements. You can create an HTML form with input fields using the following ROW blocks:
...
%ROW {
<input type=text name=@dtw_rconcat("I", ROW_NUM) size=10 maxlength=10>
%}
...
Because you created INPUT fields, you would probably want to access the values that the user entered when the form is submitted to your macro for processing. You can code a loop to retrieve the values in a variable length list:
<PRE>
...
@dtw_assign(rowIndex, "1")
%while (rowIndex <= rowCount) {
The value entered for row $(rowIndex) is: $(I$(rowIndex))
@dtw_add(rowIndex, "1", rowIndex) %}
...
</PRE>
Net.Data first generates the variable name using the I$(rowIndex) reference. For example, the first variable name would be I1. Net.Data then uses that value and resolves to the value of the variable.
Example 3: A variable reference with nested variable references and a function call
%define my = "my" %define u = "lower" %define myLOWERvar = "hey" $($(my)@dtw_ruppercase(u)var)
The variable reference returns the value of hey.