This document provides an introduction to customizing views using Views hooks and handlers in Drupal. It begins with an overview of the target audience and goals. It then covers Views hooks, which allow modifying views at different stages of processing, and Views handlers, which allow creating custom fields, filters, and other components. Examples are provided for a custom date filter handler and date field handler related to tracking zombies. The document concludes with tips on documentation and contacting the author.

1. A Gentle Introduction
to the Views API
Dan Muzyka
dan@danmuzyka.com
drupal.org/user/48685

2. Target Audience
Experience creating views through the UI
Basic working knowledge of PHP
Basic understanding of object-oriented PHP helpful, not
required
No Views development experience

3. What we will cover
How to act upon and change Views using Views hooks
Building blocks for creating your own custom fields
and filters (and by extrapolation, your own custom
sorts, arguments, etc.)

4. What we will not cover
How to use the Views UI
How to theme views

5. Background
Drupal themer and site builder for several years
Module development for about a year
Needed to do highly custom views for a client

6. Checking Documentation

8. Better, but without a conceptual
overview I don't understand this.

9. Much
better!

10. Goals
Provide conceptual overview
Show where to find documentation
Give tips for searching and deciphering Views code
Illustrate the concepts with examples
Equip you to learn more on your own
Strike a balance between clarity and not insulting your
intelligence

11. Example Use Case
Zombie Outbreak!
Report of zombies reanimated and destroyed, and
number of brains consumed
Image “Brackishfairy of the DEAD” by Shannon Hayward used under a Creative
Commons Attribution 2.0 License
http://www.flickr.com/photos/sketchink/2314369576/

12. Modules Used
Views (Duh!)
CTools
Advanced Help
Devel
Field Collection
Date
Drush

13. Views API Overview
Views Hooks



Procedural programming
Syntax familiar to
module developers and
to themers who use
preprocess functions
Useful for simple
overrides and for
exposing data to Views
classes
Views Classes and Objects


Object-oriented PHP
Useful for creating
custom fields, filters,
sorts, arguments,
relationships, etc.

14. Good Overview of Views
Hooks and Classes
Chapter 11

15. Views Hooks
Absolutely, positively essential: hook_views_api()
(This goes in zombies.module)

16. Views Hooks
Merlinofchaos recommends putting your other hooks in
mymodule.views.inc

17. Views Hooks
A lot of useful views hooks intercept and change a
view as it's being built
Each of these hooks acts on the view at a particular
stage of the 'Views Lifecycle'

18. Views Lifecycle Hooks
View Phase
Hook Run Before
Hook Run After
Use
pre_execute()
hook_views_pre_view()
NA
Affect the view early in its lifecycle
build()
hook_views_pre_build()
hook_views_post_build()
Affect the view immediately before or
after it builds the query
execute()
hook_views_pre_execute()
hook_views_post_execute()
Affect the view immediately before or
after the query runs
render()
hook_views_pre_render()
(Themes can also use this
hook)
hook_views_post_render()
Affect the view immediately before or
(Themes can also use this hook) after the HTML markup is generated

19. Learning about Views
Lifecycle Hooks
Method 1: Contrib Module API Documentation Sites (e.g.
drupalcontrib.org)



Yes, you get SOME information by searching for
hook_views_pre_build, hook_views_pre_execute, etc.
BUT, you get more context by seeing where these hooks
are invoked in the view build process
Search for:

view::pre_execute

view::build

view::execute

view::render

20. Learning about Views
Lifecycle Hooks

21. Learning about Views
Lifecycle Hooks
Method 2: Look at where the hooks are invoked in the
view object

You can find the $view->pre_execute(), $view->build(),
$view->execute(), and $view->render() methods in:
views/includes/view.inc

22. Sample from
views/includes/view.inc

23. Views hook examples
with Zombies!!!

24. Views Handlers
Create custom:

Fields

Filters

Sorts

Arguments

Etc.

25. Adding a Handler

Create the handler file

Make Drupal aware of your handler

Expose your data to your handler

Clear cache!

26. Adding a Handler
First, an overview of each step
Then, an example with the zombie view

27. Creating a Handler File
Find an existing handler similar to what you want to
create
Copy the file with the handler definition into your
module directory
Rename the handler file
merlinofchaos recommends this naming convention:
[module]_handler_[type]_[tablename]_[fieldname]
(You don't actually have to be this verbose)

28. Creating a Handler File

Change the class name in the handler file

Delete the functions you don't want to override

Edit the functions you DO want to override

29. Making Views Aware
of Your Handler
Drupal 6 method: hook_views_handlers()

30. Making Views Aware
of Your Handler
Drupal 7 method: Load in your module's .info file

31. Exposing Data
to Your Handler

hook_views_data()



Use to create new handlers (e.g., a new field you can add
through the Views UI)
Expose data from the database that is not already
exposed to Views
hook_views_data_alter()


Use to force existing fields, filters, etc to load your
handler instead of the existing handler -orChange the data exposed to the existing handler

32. node_views_data() excerpt

33. hook_views_data()
Documentation
Excellent resource: advanced_help
help/views/api-tables

34. hook_views_data_alter()
Easier place to start – just override an existing handler
Figuring out what to override
1. Determine the existing handler: dpm($view) inside one
of the Views lifecycle hooks
2. Determine where in the $data array to put your override:
dpm($data) in hook_views_data_alter() and clear cache

35. Slightly Contrived Example:
Custom Date of Destruction Field

36. Class Inheritance
in Field Example
zombies_handler_field_field_data_field_destruction_date
views_handler_field_field
views_handler_field
views_handler
views_object

37. Handler Method
Documentation
A few commonly-used methods documented in
advanced_help
Drupalcontrib.org: search for
class_name::method_name (e.g.
views_handler_field_field::render_items)
Comments in the code itself

38. When in doubt, dpm() everything

39. Less Contrived Example:
Custom Date Filter

40. Filter Handler Example
Default filter: zombie destruction date >= input date
If the zombie destruction date is NULL (zombie has not
been destroyed, yet), this does not give us result we
want

41. Filter Handler Example
Add new check box in admin UI:
'Allow content with an empty date field to pass filter'

42. Class Inheritance
in Filter Example
zombies_handler_filter_field_destruction_date
date_views_filter_handler_simple
views_handler_filter_date
views_handler_filter_numeric
views_handler_filter
views_handler
views_object

43. Recap

44. Views Hooks
Make Views aware of your module: hook_views_api()
Act on your view during the view build process: Views
lifecycle hooks
Provide data to your handlers: hook_views_data() and
hook_views_data_alter()

45. Views Handlers
Provide custom fields, filters, sorts, arguments,
relationships, etc.

46. Documentation
advanced_help
Comments and code in the
Views module itself

47. Documentation
Each of these sources has areas of strength and
weakness; if you don't find a helpful answer in one,
try another

48. General Tips
When in doubt, dpm() everything
grep through the Views directory to find the closest
ancestor class that defines the function you want to
override

49. Credits
Artwork by Shannon Hayward used under a Creative Commons
Attribution 2.0 license
Brackishfairy of the DEAD:
http://www.flickr.com/photos/sketchink/2314369576/
JASON of the DEAD:
http://www.flickr.com/photos/sketchink/2776234924/
RANDI of the DEAD:
http://www.flickr.com/photos/sketchink/2776238718/
Untitled: http://www.flickr.com/photos/sketchink/5476952538/
Untitled: http://www.flickr.com/photos/sketchink/5476953706/

50. Credits
Miles, E., Miles, L., Hogbin, E. J., & Stevenson, K. (2011). Drupal's
building blocks: Quickly building web sites with CCK, Views,
and Panels. Upper Saddle River, NJ: Addison-Wesley.

51. How to Stalk Me
dan@danmuzyka.com
drupal.org/user/48685
groups.drupal.org/user/8040
@danmuzyka
facebook.com/danmuzyka
linkedin.com/in/danmuzyka
IRC: danmuzyka

52. Questions?