Creating dynamic forms in QGIS

When you edit the fields of a layer in QGIS, you have the option of using a spreadsheet-like table view or a database-style form view. Forms are useful because you can change the design of the form, and you can add interactive features which react to user input to better control data editing. In this recipe, we'll add some custom validation to a form that checks user input for valid values.

Getting ready

You will need to download the following zipped shapefile and decompress it to a directory named ms in your qgis_data directory:

https://github.com/GeospatialPython/Learn/raw/master/MS_UrbanAnC10.zip

You'll also need to create a blank Python file called validate.py, which you'll edit with the following steps. Put the validate.py in the ms directory of your qgis_data directory with the shapefile.

How to do it...

We'll create the two functions we need for our validation engine. Then, we'll use the QGIS interface to attach the action to the...