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Models live in components

Create a component

Up to now, the example presented was just a simple file containing application code and a test. This is not representative of the code you’d find in an actual project. In an actual project, your code would always be part of a component, as discussed previously.

It is time to create a component for our project, and put the code for our model in there. We’ll skip testing further until a bit later, so just go ahead and create a project as before, with our new model code in a file called

Register the models that live there

A model lives in a Reahl component – like any other class. Models that are mapped via SqlAlchemy to underlying database tables require one more step though. You have to inform Reahl as to which of the classes in a particular component map to relational database tables. This is necessary because the command line tools perform certain tasks that need this information as input. These tasks include creating the database schema or creating or dropping tables, for example.

To make the Reahl infrastructure aware of the persisted classes in a component, you must add a list of <class> tags inside a single <persisted> section in the .reahlproject file of the component in which the code lives:

    <class locator="reahl.doc.examples.tutorial.addressbook1.addressbook1:Address"/>

For each class, a locator is specified. The part of the locator after the ‘:’ is the Python class you want to list, and the part before the ‘:’ is the Python module where that class is to be found.

Housekeeping and your database schema

Whenever you change a .reahlproject file though, be sure to run (for that project):

reahl setup -- develop -N

Your Python Egg’s meta information is regenerated from the .reahlproject file when setup is run like this.

Of course, at this point your database schema needs to be updated to include tables for this new class. Thus, you need to run:

reahl-control createdbtables etc


The createdbtables command will only succeed if you have not run it before. In this case you can always undo your previous run before you re-create the tables, by running:

reahl-control dropdbtables etc

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