Do you recall referencing graph parameters using the ${PARAM} syntax? Using inline CTL expressions is even simpler! Let’s assume you’d like to store some data records to a unique file every day, e.g. orders_2009-09-16.dat. Changing the file name every day might be pretty annoying. Well, it’s much more pleasant to use an inline CTL expression. Take UniversalDataWriter for example and simply set its fileURL attribute to something like this:

${DATAOUT_DIR}/orders_`date2str(today(), "yyyy-MM-dd")`.dat

Notice the `date2str(today(), "yyyy-MM-dd")` part — that’s an inline CTL expression. Yes, that’s all you need to do! Just enclose your CTL expression within back quotes and place it anywhere you like. Except CTL transformations of course, that would be meaningless.

The good news is that you can reference graph parameters from inline CTL expressions. Such graph parameters might again contain CTL expressions. And so forth… Assuming you defined parameters FIRST_NAME and LAST_NAME, defining another parameter, let’s say FULL_NAME, in the following way is perfectly valid:

`substring('${FIRST_NAME}', 0, 1)`. ${LAST_NAME}

Beware, two adjacent back quotes are treated as an empty CTL expression and always evaluated to an empty string. You might also ask how to use back quotes within inline CTL expressions. Well, it’s pretty straightforward, just escape them using a back slash, i.e. \`. (Both these features work since version 2.8.1.)

By default, evaluation of inline CTL expressions is turned on. If you want to turn this feature off for any reason, you can simply do so by setting the GraphProperties.EXPRESSION_EVALUATION_ENABLED configuration property to false.

We hope you’ll find this brand new feature useful! You can let us know where and why you use it by leaving a comment to this post.