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Facilitator Training http://eden.sahanafoundation.org/wiki/GHC2010
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GHC
- Sahana Eden: Emergency Development Environment 15 September 2010, Grace Hopper Celebration Fran Boon [email_address]
- eden module resource
- Sahana Eden: Session 2 15 September 2010, Grace Hopper Celebration Fran Boon [email_address]
- Branches LaunchPad Merge proposal Trunk Local Branch Your Branch bzr merge bzr push
- URL(a= application , c= controller , f= function , args=[], vars={})
- RHeader Tabs
- End
- S3 is built on Web2Py REST CRUD SQLFORM FORM
Editor's Notes
- S3 is a codename for Sahana Eden Server & Client can be on the same machine Each part needs to be debugged separately: Eclipse works well for the Server-side Python, whilst Firebug is excellent for the generated HTML/CSS/JavaScript JavaScript libraries we use include jQuery & ExtJS
- There are notes on the Wiki for installing a developer environment on Windows, Mac or Linux machines if you wish to run in other environments later.
- Look around the filesystem in web2py/applications/eden folder Similar layout structure to other MVC frameworks, such as Ruby-on-Rails & Django
- JavaScript which doesn’t require server-side parsing put into static Python Libraries available: System Python, Web2Py, Eden (S3*)
- For each of these, you should find at least 1 Model, a single Controller & a folder containing 1 or more Views
- Minimise the time taken to process Manage dependencies No need to import most of the libraries in ‘gluon/’
- Sahana Eden is a Resource-centric application: Persons, Locations, etc
- Create a new file in the Models folder called ‘vts.py’ & type in the text above. Remember that whitespace matters! # Text after this symbol is a comment & is ignored If you make a mistake, then the Ticketing system should catch the error & let you know what you did wrong.
- No need to create a manual routes entry, unlike other frameworks, like Django
- Create a new file in the Controllers folder called ‘vts.py’ & type in the text above.
- Note that you’ll need to Register yourself as a user on the system before you’re allowed to create a resource. The 1 st user to register gets the Administrator role by default.
- Web Services, Mash-ups
- Minimise the time taken to process Manage dependencies No need to import most of the libraries in ‘gluon/’
- Deleted Columns / Tables simply Ignored
- Take a look at them now Remember that execution order is defined by alphabetical order
- Take a look at them now
- Take a look at them now
- These defaults are why we didn’t need any views for our application.
- No need to learn another macro language Can Extend just a single other file Can Include many others
- Create a new folder in the views folder called ‘vts’ & inside that put a new file ‘vehicle_list_create.html’. Type in the text above. Refresh the vehicle page to see the new text: http://127.0.0.1:8000/eden/vts/vehicle
- Open the About page & browse the variables We store our S3 variables in response.s3.*, session.s3.* so as not to pollute the Web2Py namespace
- unique=True is a SQL-level constraint. Open your vts.py from the models directory & add the extra code above. Validators are DAL-level constraints which produce nice error messages instead of tickets! Validators provide server-side validation & some also provide client-side rendering & validation Web2Py automatically adds a Validator when the SQL constraint is set.
- Fields default to type ‘string’. ‘ date’ is the SQL-level field type & also provides the class in the HTML which means we get a date widget Add the extra code above to your file & refresh the page, now enter a date.
- Add the extra code above to your file & refresh the page to see the default value
- Add this to your model (underneath the table definition) & try it out
- You can check out the languages file, if you wish: http://127.0.0.1:8000/admin/default/design/eden#languages Update all languages
- Add this to your model (underneath the table definition) & try it out Comment is rendered as ‘column3’ (although can be moved using ‘formstyle’) We also use the same space for Help buttons & ‘Add New Resource’ links. NB For optimal performance, we normally add such comments in the Controller instead & put them inside a ‘prep’ to tale effect just when ‘r.representation in shn_interactive_view_formats’
- Try them out…copy/paste from another controller & then edit…see what effect this has on your module.
- This should be available as a script or an alias ‘w2p’ iPython needs to be installed for object exploring.
- Normally you work in a local branch on your PC. You Merge changes in regularly from Trunk. You Push your changes to your branch on LaunchPad (You Pull from LaunchPad to update your server sites)
- URL() is an example of an HTML ‘Helper’ object Remember that after server-side Python finishes, we still have a lot of possibilities client-side with JavaScript.
- Add this text to the file 000_config.py in the models folder. Navigate to the home page to see the module appear both there & on the menu. Try navigating to the module. Module Type 10 means appears in the ‘more’ section of the default modules menu. (Most deployments will create a fully-customised menu anyway)
- Add this text to your controller file & now open the module. “ Custom View” is a Doc String One should be added to all functions for automatic documentation generators & interactive browsing of docs You can try this out in the Interactive Shell: w2p execfile("applications/eden/controllers/vts.py", globals()) help(index)
- Create a file called ‘index.html’ inside the views/vts folder See plain HTML being interspersed with the server-side parsed Python Look at another module’s index.html What’s bad about this index?
- Add this text to your controller (outside the functions – e.g. at the top) & see what effect this has on your module.
- Google: web2py dal Try these out in the Web2Py shell Don’t take effect until you db.commit() Beware locking with Sqlite! (e.g. cron tasks) Wipe DB if developing a lot For Production, split Dev/UAT/Prod instances so that you can plan Data Migrations (Live migrations works in most cases, but some do need manual scripts still – not a complete ‘Get out of jail free’).
- Don’t take effect until you db.commit()
- Copt this text into your model. Note the use of string substitution to define the tablename
- Tells SQL that these fields are ‘reference’ fields (i.e. Foreign Keys) - They store integers which are a pointer to the ID field in the other tables.
- Copy this text into your Model & refresh the presence page Reusable field defined in models/03_gis.py Includes additional useful configuration such as .requires & .represent
- Copt this text into your controller. Try it out. Note the automation of the resource name to minimise the editing after copy/paste of new functions
- Copy this text into your model & see what it does for the page IS_ONE_OF() will provide us a dropdown showing license plates, even though we actually store the ID. This is an S3 validator which extends Web2Py’s IS_IN_DB() to support the ‘deleted’ status & also allow the use of lambdas as formatting options.
- We can add additional fields into the link table.
- IS_ONE_OF provides the representation in the dropdown table.field.represent provides the representation in Display/List views A lambda is a Python feature for defining anonymous functions on the fly: http://diveintopython.org/power_of_introspection/lambda_functions.html
- Optimise the query – we know we only want a single record & a single field from that record
- Add the optimised query to your model.
- Add this to your model underneath the definition of the Presence table & try out the URL. No need for dedicated presence() controller
- Add this Resource Header definition to your Controller. Be careful to get the end brackets & commas right! ‘ r’ is the resource
- Then plug it into the Controller
- Take a look at the HTML structure of the page in Firebug.
- Web2Py source code very accessible – small enough to be able to grasp the whole thing after not too long FORM defined in gluon/html.py: Dumb HTML elements SQLFORM defined in gluon/sqlhtml.py: Self-processing forms which update the database CRUD defined in gluon/tools.py: Wrappers around SQLFORM - We actually change CRUD a lot & are looking to remove it completely – building straight on top of SQLFORM() REST defined in modules/s3xrc.py: RESTful interface & XML representations If you drop down a level, then need to do things more manually & need to take care of framework issues yourself.
- Whilst we spend a lot of time updating developer documentation, the actual codebase always moves faster, so the source is always the most authoritative source of information.