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March 08, 2010
Problem with one-class-per-file approach
Hi folks,

Allow me to introduce myself, I'm Kris and new to this list and the D language in general, but have well over 20 years of programming experience using several other languages ranging from Wozniaks' integer basic to Hejlsbergs' c#.

My first venture using D is to create a set of classes implementing XML DOM using familiar syntax for people used to php or javascript and such. I was able to write the basics for this in D in a few hours using a bunch of classes:

- XMLDocument
- XMLNode
- XMLAttribute
- XMLElement
- XMLTextNode
- XMLComment
- XMLCDataSection
- XMLNodeList
- XMLAttributeList

All in the package "red.xml"

Being used to (and really liking!) the one-class-per-file approach, I instinctively created the classes in seperate files. When attempting to compile a simple test program however it quickly became totally unrealistic to use the one-class-per-file approach because I had to import each and every single file seperately in order to get a working build. When I moved all the classes into a single module (red.xml.xmldom) it worked flawlessly but I would really like to have the best of both approaches.

Is it possible to split the files up to use one class per file again, but add a red.xml.xmldom module imports and exposes them somehow?

I was hoping it'd be something like the following in the red.xml.dom module:

import red.xml.xmldocument;
import red.xml.xmlnNode;
import red.xml.xmlattribute;
import red.xml.xmlelement;
import red.xml.xmltextnode;
import red.xml.xmlcomment;
import red.xml.xmlcdatasection;
import red.xml.xmlnodelist;
import red.xml.xmlattributelist;

But that doesn't seem to work (I get a whole bunch of "module ... is in multiple defined" errors).

I'm compiling with the latest dmd compiler on the commandline in macos x (10.6) using a commandline tool I built in php that compiles a file "main.d" and adds all imported dependencies to the dmd commandline. The generated commandline statement looks like this:

dmd -of/Users/kris/Developer/D/xml-tests/main -unittest /Users/kris/Developer/D/xml-tests/main.d /Users/kris/Developer/D/xml-tests/red/generic/linkedlist.d /Users/kris/Developer/D/xml-tests/red/xml/xmlnode.d /Users/kris/Developer/D/xml-tests/red/xml/xmldocument.d /Users/kris/Developer/D/xml-tests/red/xml/xmlattribute.d /Users/kris/Developer/D/xml-tests/red/xml/xmlattributelist.d /Users/kris/Developer/D/xml-tests/red/xml/xmlelement.d /Users/kris/Developer/D/xml-tests/red/xml/xmltextnode.d /Users/kris/Developer/D/xml-tests/red/xml/xmlcomment.d /Users/kris/Developer/D/xml-tests/red/xml/xmlcdatasection.d /Users/kris/Developer/D/xml-tests/red/xml/xmlnodelist.d /Users/kris/Developer/D/xml-tests/red/xml/dom.d

more readable:

dmd -ofmain -unittest main.d 
	red/generic/linkedlist.d 
	red/xml/xmlnode.d 
	red/xml/xmldocument.d 
	red/xml/xmlattribute.d
	red/xml/xmlattributelist.d
	red/xml/xmlelement.d
	red/xml/xmltextnode.d
	red/xml/xmlcomment.d
	red/xml/xmlcdatasection.d
	red/xml/xmlnodelist.d
	red/xml/dom.d

I've also tried versions omitting the dom.d (same errors), and adding only dom.d (lots of "identifier ... is not defined" errors), but nothing works the way I'd hope and/or expect.

Is there any clean way to do this?

I can make my sourcecode available if anyone would like that (for the build tool as well).
March 08, 2010
Re: Problem with one-class-per-file approach
Kris Herlaar:

> Allow me to introduce myself, I'm Kris and new to this list and the D language in general,

Welcome here and to D then.


> Being used to (and really liking!) the one-class-per-file approach, I instinctively created the classes in seperate files.<

D gives you the freedom, if you want, to put single classes in files, but the normal D idiom is to put related classes in a single module (if they aren't too much long).
And keep in mind that in D there are also free functions (and templates, inner functions, true closures, etc), so you don't need to use classes for everything.


> import red.xml.xmldocument;
> import red.xml.xmlnNode;
> import red.xml.xmlattribute;
> import red.xml.xmlelement;
> import red.xml.xmltextnode;
> import red.xml.xmlcomment;
> import red.xml.xmlcdatasection;
> import red.xml.xmlnodelist;
> import red.xml.xmlattributelist;

You can also write:
public import red.xml.xmldocument,
             red.xml.xmlnNode,
             red.xml.xmlattribute,
             ...
             red.xml.xmlattributelist;



>I'm compiling with the latest dmd compiler on the commandline in macos x (10.6) using a commandline tool I built in php that compiles a file "main.d" and adds all imported dependencies to the dmd commandline.<

There are several already written programs to do that :-) For example I use 'bud', there is also rdmd built in the distribution.

Bye,
bearophile
March 09, 2010
Re: Problem with one-class-per-file approach
Hello Kris,

> Hi folks,
> 
> Is it possible to split the files up to use one class per file again,
> but add a red.xml.xmldom module imports and exposes them somehow?

Take a look at the details of import. IIRC "public import" does something 
like what you want.

> 
> I was hoping it'd be something like the following in the red.xml.dom
> module:
> 
> import red.xml.xmldocument;
> import red.xml.xmlnNode;
> import red.xml.xmlattribute;
> import red.xml.xmlelement;
> import red.xml.xmltextnode;
> import red.xml.xmlcomment;
> import red.xml.xmlcdatasection;
> import red.xml.xmlnodelist;
> import red.xml.xmlattributelist;
> But that doesn't seem to work (I get a whole bunch of "module ... is
> in multiple defined" errors).

I don't know what's causing that, but my first guess would be to add module 
"red.xml.whatever;" lines to each module.

-- 
... <IXOYE><
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