How to construct objects based on XML code?

Question

I have XML files that are representation of a portion of HTML code.
Those XML files also have widget declarations.
Example XML file:

 <message id="msg">
   <p>
     <Widget name="foo" type="SomeComplexWidget" attribute="value">
        inner text here, sets another attribute or 
        inserts another widget to the tree if needed...
     </Widget>
   </p>
 </message>

I have a main Widget class that all of my widgets inherit from.
The question is how would I create it?
Here are my options:

1. Create a compile time tool that will parse the XML file and create the necessary code to bind the widgets to the needed objects.
   • Advantages:
     • No extra run-time overhead induced to the system.
     • It's easy to bind setters.
   • Disadvantages:
     • Adds another step to the build chain.
     • Hard to maintain as every widget in the system should be added to the parser.
     • Use of macros to bind the widgets.
     • Complex code
2. Find a method to register all widgets into a factory automatically.
   • Advantages:
     • All of the binding is done completely automatically.
     • Easier to maintain then option 1 as every new widget will only need to call a WidgetFactory method that registers it.
   • Disadvantages:
     • No idea how to bind setters without introducing a maintainability nightmare.
     • Adds memory and run-time overhead.
     • Complex code

What do you think is better? Can you guys suggest a better solution?

Answer 1

I am not sure about the variants you've posted, but the easiest approach (not the most efficient, more like "get-it-done" approach) would be writing your loading wrapper for boost::serialization library.

In this case you would have to call to your deserializing routine, point the file (or it's mapped part) and retrieve a constructed object that can be registered in your widget container.

Note that you probably won't need to write the appropriate saving (serializing) routine, only the loading one.

Also note that you could combine some easy (maybe self-implemented) parser with your deserializing routine, so that, for example the first one grabs the code related to your Widget and the second one constructs an object from it.

Answer 2

Create the tool, include it into your build steps and everything will be fine.

See comments to my previous answer for additional details.