DTML also offers a way to call other DTML methods from within your code, via the <dtml-call> construct. This comes in particularly handy when you want to invoke a method, but aren't really all that concerned about displaying the results of that method to the user - SQL queries are a prime example of this.
Consider the following example, which demonstrates:
<dtml-var name> has been added to your DVD collection!</h1>
href="listMovieCollection">List Movies in your Collection</a></p>
In this case, I've called the addMovieToCollection() Z-SQL method. This method
adds a record to the table containing my DVD collection. However, since I don't really need to worry about the return value, I can use the <dtml-call> tag to invoke the Z-SQL method.
Note also that I am not explicitly passing any parameters to the Z-SQL method. In this scenario, Zope take cares of extracting the required data from the REQUEST namespace and passing the parameters to the invoked method automatically. Isn't that neat?
There is a caveat, though - invoke the same method in an expression, and your workload increases. Why? Because now it's up to you to pass the parameters to the method explicitly.