Re: Impressions of EGL - Part Duex

[Joe Pluta <joepluta@xxxxxxxxxxxxxxxxx>]

Nathan Andelin wrote:
> Joe, you seem to have a misconception about HTML templates used by 
> CGIDEV2 and similar toolkits.  They're much different than the "tagging 
> approach" used by Java frameworks.  But you can do the research 
> yourself; I just mention it as an aside.
>   
I'm quite comfortable with HTML templates, Nathan.  They're fragments of 
HTML with substitution areas marked.  I'd be interested to see what you 
see as the difference between a CGI substitution tag, a tag in a 
framework like Tapestry, and a <%= %> substitution in JSP.

> I really wanted to ask about the "no work on your part".  What about 
> defining EGL records?  And what is it that automatically binds them to 
> fields on the page?
>   
The record is the central concept in EGL (as it should be in any 
business language).  EGL supports metadata: it allows you to define not 
only the data and its type, but also things like the field prompt and 
the validation logic.  The code to support all of this is automatically 
generated when you drop a field on a page, whether it's a standalone 
field, a record, or an array of records.

The binding is done automatically; there is no need to call ZbhGetVar 
(or its equivalent) to retrieve the data.

> If an RPG program uses templates, you'll see code like the following 
> that inserts field values into a page:
>
> rptVarSet('type':%trimr(codetype));
> rptVarSet('desc':%trimr(typedesc));
>
> Notice that the API also allows the %trimr() function to be called, but 
> it could just as well be any other type of data formatting, or even 
> decrypting the field before outputting it.  Or if the user is not 
> authorized to see the field, an empty value could be returned.  Or the 
> statement could be conditional.  This is quite powerful on the one hand, 
> and perfunctory on the other.  It's the type of code you could do when 
> your half asleep.
>   
But it's also the kind of code that gets you in trouble.  There's no 
checking, and it's quite easy to put the contents of the wrong field 
into the HTML page.  In your case, you have to know that the HTML tag 
"desc" is supposed to contain data from the field "typedesc", not 
"itemdesc".  It's an extra manual binding step that's very easy to do 
incorrectly.  With EGL, you simply drop the record on the page, and EGL 
makes sure the HTML contains the data from the record.

EGL also knows about JSF, much moreso than CGIDEV.  Here's a VERY simple 
example.  I created a radio button group using JSF (I did this yesterday 
in a demo for a user group).  The button group had four buttons: Dogs, 
Cats, Birds and Iguanas.  I bound that select field to a string field in 
my EGL program with a simple point and click.  Now, if I set the field 
to "Dogs", the appropriate radio button in the group is selected.

How would you do that in CGIDEV?


> And if it's just too perfunctory, you could write a procedure to 
> automatically map fields from an externally defined data structure to 
> fields on the page with a single function call, which is what the folks 
> at cnxcorp did in their Valence RPG toolkit.
>   
But you don't need a toolkit.  EGL does it for you.  And it does a lot more.

Joe