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Customizing generated code

Although ArchGenXML builds all the necessary boilerplate to create Plone Archetypes-based content types, there are some pieces of code that we can't specify anywhere in a UML model. Fortunately, we can modify the automatically generated code in different places so that ArchGenXML won't overwrite it in future builds.

Typical examples of code customization are setting the order of the widgets in the edition form and defining the body of complicated methods.

Getting ready

Every time we customize ArchGenXML-generated code, we must do it inside the special comment blocks placed everywhere in the source files like the following:

##code-section class-header #fill in your manual code here
##/code-section class-header

##code-section module-footer #fill in your manual code here
##/code-section module-footer

Note

Notice the #fill in your manual code here legend.

How to do it…

We will first define the order for the widgets when displayed in standard edit form and view page.

Go to the models/poxContentTypes/content folder inside your ArchGenXML installation directory and open XNewsItem.py file in your favorite code editor.

Find the following comment block placed just after the definition of XNewsItem schema:

##code-section after-schema #fill in your manual code here
##/code-section after-schema

Add the following lines to alter the order of the widgets in the resulting schema:

##code-section after-schema #fill in your manual code here
XNewsItem_schema.moveField('lead', after='title')
XNewsItem_schema.moveField('country', before='text')
XNewsItem_schema.moveField('relatedItems', pos='bottom')
##/code-section after-schema

Look at the highlighted lines:

We get lead field and put it next to the title.
Then we get country field and place it before the body text field.
Finally, we get relatedItems field and send it to the bottom of the schema.

We have only one method in our XNewsItem class: countryVocabulary. For teaching purposes, we have defined its body as a line of code returning just three countries (check Creating a model). However, we are now going to add more options. We could actually get and return a list of countries from somewhere, like a special tool in Plone or even a Web service. Instead, we are just going to increase the list with a static one. This is the way ArchGenXML lets us define the body of complicated methods.

We must first remove the body of the method in the UML model:

Select the countryVocabulary method in the operations panel (the third one in the XNewsItem class).
Open the Tagged Values tab in the bottom-right panel.
Remove the code tagged value and its associated value. Place the cursor in the corresponding row and press the trash icon. Be sure to remove not the contents but the whole row to prevent ArchGenXML parsing errors.
Open XNewsItem.py file again (inside models/poxContentTypes/content folder) and locate the countryVocabulary definition line.

You'll see the old three-country list. Remove it and modify the code as follows:

security.declarePublic('countryVocabulary')
def countryVocabulary(self):
    """
    Returns a list of country codes and their names for the "country" field
    """

    return (\
            ('AQ', 'Antartiqa'),\
            ('AR', 'Argentina'),\
            ('BS', 'Bahamas'),\
            ('BR', 'Brazil'),\
            ('CM', 'Cameroon'),\
            ('CL', 'Chile')\
            )

How it works…

ArchGenXML is so great that if there's no way to turn UML into code, it lets us insert our own code in places that won't be modified in subsequent builds.

In the procedure above, we covered two typical examples of code customization.

In Steps 1 to 3, we moved the fields we used in Creating a model to be placed exactly where we wanted.

Although we can set widgets order via tagged values, we wanted to show how to do this for other Archetypes content types that might be created without ArchGenXML.

Note

To learn how to use move:after, move:before, move:bottom, move:top, and move:pos tagged values, check the documentation at http://plone.org/documentation/manual/archgenxml2/reference/tagged-values.

As you may have guessed, moveField is a schema method aimed to place the fields in the order we want. If we don't use this method, fields' widgets will be placed in the order of declaration in the source file. In our case, due to the way that ArchGenXML generates the final schema, the News Items inherited fields are placed first followed by the fields we added manually in the UML model.

In Steps 4 to 8, we modified the body of a method with a more complicated functionality. If ArchGenXML finds a piece of code for a method, it won't try to write its body even if there's a code tagged value defined in the UML model. However, it's a good practice to keep things clean and clear.

Because we have placed these two changes in special parts of the source files (Step 3 above), ArchGenXML won't touch them in next runs.