Sahana Eden : Introduction to the Code (SahanaCamp 1.2)
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Sahana Eden : Introduction to the Code (SahanaCamp 1.2)
- 1. Sahana Eden: Introduction to the Code 5 November 2010, Sahana Camp Fran Boon fran@sahanafoundation.org
- 2. Emergency We have to build an application by lunchtime!
- 3. Agenda • Web2Py execution model • S3 REST Controller – Model – Controller – View
- 4. Web2Py Execution Model 1. All Models executed every request – In alphabetical order – Within web2py environment 2. The Controller is executed 3. The View template is parsed 4. (HTML) page returned to client
- 5. Models • Define Tables in Database Live Migrations: - Tables created/altered in database
- 6. Resources • Common Resources from other Models – Person • Group – Location – Organisation – Site • Hospital • Shelter
- 7. S3 REST Controller • Args: – /update, /create, /delete • HTTP verbs: – GET, PUT (POST), DELETE • Representations: – .html, .json, .xml, .xls, .pdf
- 8. Adding a new application • Vehicle Tracking System • Name: vts • Resources: – vehicle – driver – location
- 9. Model: Define Table models/vts.py # Vehicle resource table = db.define_table("vts_vehicle", Field("registration"), Field("make"), Field("model"), Field("supplier"), )
- 10. Controller: S3 REST controllers/vts.py def vehicle(): return s3_rest_controller("vts", "vehicle")
- 11. View None needed at 1st – can RAD without them & then polish later Try: http://127.0.0.1:8000/eden/vts/vehicle 1. Create a vehicle. 2. View in different formats: – .json, .xml, .xls, .pdf
- 12. Coffee
- 13. Views: S3 REST • REST has default views – create.html – display.html – list.html – list_create.html – update.html
- 14. Views • Python code inside {{ }} is parsed server- side • Views can extend & include other views • Extend ‘layout’ for overall look/feel {{extend "layout.html"}}
- 15. Views: Custom • They can also be customised: views/vts/vehicle_list_create.html {{extend "layout.html"}} {{rheader="Register a new vehicle in the system:"}} {{include "_list_create.html"}}
- 16. Model: SQL constraints models/vts.py table = db.define_table("vts_vehicle", Field("registration", unique=True), Field("make"), Field("model"), Field("supplier"), )
- 17. Model: Field Types models/vts.py table = db.define_table("vts_vehicle", Field("registration", unique=True), Field("make"), Field("model"), Field("purchase_date", "date"), Field("supplier"), )
- 18. Model: Default Values models/vts.py table = db.define_table("vts_vehicle", Field("registration", unique=True), Field("make"), Field("model"), Field("purchase_date", "date", default=request.utcnow), Field("supplier"), )
- 19. models/vts.py … db.vts_vehicle.registration.label = T("License Plate") Labels
- 20. Controller: Comment controllers/vts.py def vehicle(): db.vts_vehicle.registration.comment = DIV(_class="tooltip", _title="Help text here") return s3_rest_controller("vts", "vehicle")
- 21. How do we Navigate? • Modules menu • Modules list on frontpage • Menu within Module
- 22. Enable Module models/000_config.py deployment_settings.modules = Storage( … vts = Storage( name_nice = "Vehicle Tracking System", description = "Track vehicles", module_type = 10 ), … )
- 23. Index page controllers/vts.py module = request.controller def index(): "Custom View" module_name = deployment_settings.modules[module].name_nice return dict(module_name=module_name)
- 24. View views/vts/index.html {{extend "layout.html"}} {{=H2(T(module_name))}} <p>This module allows users to track their vehicles</p> {{=LI(A("List Vehicles", _href=URL(r=request, f="vehicle")))}}
- 25. Controller: Menu controllers/vts.py response.menu_options = [ [T("Vehicles"), False, URL(r=request, f="vehicle"),[ [T("List"), False, URL(r=request, f="vehicle")], [T("Add"), False, URL(r=request, f="vehicle", args="create")] ]]]
- 26. Lunch
Hinweis der Redaktion
- As well as being a suite of pre-built applications, Eden is also an Emergency Development Environment: a framework which can be used to rapidly build new ones to meet custom needs (as every emergency is different).
- Because all models are executed every request, it is important to minimise the amount of time taken to process them. Alphabetical order is to Manage the dependencies ‘In the Web2Py environment’ means no need to import most of the libraries in ‘gluon/’ & access to the global variables: request, session & response. First the parts of the Controller outside Functions are executed & then the relevant Function. Functions with no arguments are automatically visible via URLs No need to add a routes entry (unlike other frameworks, like Django) The Controller or View could also return XML (e.g. RSS or KML), JSON, PDF or XLS.
- Remember that after server-side Python finishes, we still have a lot of possibilities client-side with JavaScript. URL() is an example of an HTML ‘Helper’ object
- JS = JavaScript
- Deleted Columns / Tables simply Ignored Sahana Eden is Resource-centric
- Sahana Eden is Resource-centric
- Web Services, Mash-ups
- Create a new file in the Models folder called ‘vts.py’ & type in the text above. # 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.
- Create a new file in the Controllers folder called ‘vts.py’ & type in the text above.
- Note that you’ll need to Login to the system before you’re allowed to create a resource.
- These defaults are why we didn’t need any views for our application. Web2Py defaults to views/controller/function.html, but S3REST needs a different view per Method
- 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. Try adding multiple vehicles with the same registration. Validators are DAL-level constraints which provide server-side validation & some also provide client-side rendering & validation. These are automatically added with SQL constraints to produce nice error messages instead of tickets. Validators can also be added manually as: db.vts_vehicle.registration.requires = IS_NOT_IN_DB(…)
- 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 (This comes from the default IS_DATE() Validator) 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 (under the table definition) & try it out. T() is to Internationalise the string
- Add the comment to your controller & try it out
- If you have time, then you can try out these CRUD strings…copy/paste from another model & then edit…see what effect this has on your module.
- 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’).
- The alias ‘w2p’ runs: python web2py.py –S eden –M
- 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 Optimise the query – we know we only want a single record & a single field from that record
- Add this to your model underneath the definition of the Presence table & try out the URL. No need for dedicated presence() controller This can then be enhanced with the use of Tabs – look for rheader tabs in the source of other applications…
- 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.