Sahana Eden Framework

We have built an S3 framework as a higher level of abstraction on top of Web2Py.
This should be used by modules where possible, but if more power is needed then drop down a level of two (to T2, to base Web2Py or to raw Python).

Overview

• ​S3 API Documentation (Epydocs)

• Authentication, Authorization and Accounting (S3AAA)
• Extensible Resource Controller (S3XRC)

Web2py Extensions

We extend some web2py framework classes in modules/s3.
Patches to the framework should be done here.
If they're generic enough then they can be suggested to Massimo Di Pierro for moving upstream to ​web2py.

We replace web2py's Crud with a REST Controller.

Custom Methods Plugged into REST

In many cases it may be much easier to implement non-CRUD resource functions as REST-plugins instead of separate controllers.

• see search_simple for an example

The advantage of doing it as REST plugin is that you have a pre-parsed XRequest instead of the original request, as well as you'd preserve the actions and setting from your REST interface for this resource.

XRequest is already checked and parsed for the REST syntax, and is resolved for the format extension (XRequest.representation) and record ID's, contains all handles to the necessary tables as well as the complete primary record (if any).

It contains the interface to export or import the resource in XML and JSON (.import_xml() and .export_xml() resp. _json()), and of course you'd have the nice backlink helpers to quickly produce URL's:

 .here() (=URL of the current resource),
 .same() (=URL of the current resource, record ID replaced as "[id]"),
 .there() (=URL of the current resource, no function, no record ID), and
 .other() (=URL of the current resource, other function)

and finally, XRequest remembers the record ID until the next request to the same resource in the same session, which can be helpful when producing links (especially _next's) not knowing the record ID.

Mandatory

Each Controller should start like this:

module = "module"
# Options Menu (available in all Functions' Views)
response.menu_options = [
    [T("Home"), False, URL(r=request, f="index")], [
        [T("Resources"), False, URL(r=request, f="resource")],
        [T("List"), False, URL(r=request, f="person")],
        [T("Add"), False, URL(r=request, f="resource", args="create")],
        [T("Search People"), False, URL(r=request, f="resource", args="search")]
    ]]
]

Conflict Detection

Sahana is a multi-user system so there is a potential for multiple users to be editing the same record at once.
We use Web2Py's CRUD to handle this for us.

Add the timestamp reusable field to each table which needs protecting (in models/module.py):

Synchronization

All tables which are user-editable need to be protected for conflict resolution & synchronization using the predefined reusable fields timestamp & uuidstamp.

• Database Synchronization

Redirection

Remember that the interactive HTML interface is just one way to access the system. Non-interactive interfaces like Synchronization are also common, as are background interactions like AJAX.

Therefore be very wary of using Redirection, which should never be done in Validators, Onaccept or Onvalidation routines & should be done within REST Controllers only with a check:

def my_resource():
    """ REST Controller for my_resource """

    def prep(r):
        if r.representation in shn_interactive_view_formats:
            redirect ok
        ...

Optional

Other reusable fields are available to add Foreign Key links to key tables, such as:

• location_id() to add a GIS location for Mapping
• person_id() to add a Person
• organisation_id() to add a link to an Organisation

List output are made more functional by this .represent 'widget':

def shn_list_item(table, resource, action, display="table.name", extra=None):
    if extra:
        items = DIV(TR(TD(A(eval(display), _href=t2.action(resource, [action, table.id]))), TD(eval(extra))))
    else:
        items = DIV(A(eval(display), _href=t2.action(resource, [action, table.id])))
    return DIV(*items)

This is called in models/01_crud.py in the REST Controller:

db.pr_person.represent = lambda table:shn_list_item(table, resource="person", action="display", display="table.full_name")

Form labels can be set in a translatable manner using:

db.table.field.label = T("label")

Form field can be made to use a TEXTAREA by marking the field as being type 'text':

Field("field", "text"),

Form field can be made to use a SELECT dropdown by setting the field as a lookup to another table...linked to the 'id' field to allow Database Synchronization, but displaying a more user-friendly field (such as 'name'):

Field("field", db.othertable),

db.table.field.requires = IS_NULL_OR(IS_ONE_OF(db, "othertable.id", "othertable.name"))

NOTE: The IS_IN_DB validator is not deletion status sensitive, i.e. even deleted entries in the key table can be referenced. To exclude entries that are flagged as 'deleted', use the IS_ONE_OF validator.

Form field being required can be marked using:

db.table.field.comment = SPAN("*", _class="req")

Help for a form field can be set using:

DIV(DIV(_class="tooltip", _title=T("Help Title|This is what this <a href='http://wikipedia.org/Field' target=_blank>field</a> is for.")))

Different Flash styles can be set via:

session.error = T("Unsupported format!")
redirect(URL(r=request, f=resource))

or (in a Multiple Table form.accepts):

response.error = T("Form invalid!")

Supported styles are:

• .warning
• .error
• .information
• .confirmation (Default response.flash is styled like this)

Global variables

Use session for per-user persistent variables: session.s3.myvariable

Use response for one-off variables which are visible in views without explicit passing: response.s3.myvariable

Settings

System-wide settings have their default values set in models/000_config.py.

A few settings are still in the s3_settings table.

Upon 1st run of the system, these settings are loaded into the database from where they can subsequently be edited to configure the running instance.

If these settings are required by all Views then can patch the session to see them in models/00_utils.py's s3_sessions().
e.g. session.s3.debug is made available to the default layout.html this way.

If you wish to clean out all settings to import afresh, then close down Web2Py & delete all files from /databases)

Modules can set up their own configuration settings tables in a similar way (e.g. GIS does this)

jQuery

jQuery scripts are located in multiple places to provide for ease of maintenance & for performance gains:

• If there is no need for server-side processing our scripts should be added to /static/scripts/S3/S3.js
  • This gets automatically compiled into S3.min.js via: DeveloperGuidelinesReleaseProcess
• If there is a need for server-side pre-processing, they should be added to /views/sahana_scripts_debug.html
  • Also needs manually copying to /views/sahana_scripts_min.html
• Scripts from base Web2Py or T2 are stored in the appropriate areas of /static/scripts or /views/sahana_scripts_*.html

Specific widgets we use:

• dataTables plugin to enhance list output with clickable columns, pagination & search box
• autocomplete plugin for not having dropdowns get too huge (e.g. /views/msg/sms_outbox_create.html)
• Popup for Form reference data
• Subtypes in Select dropdowns
• Deletable List (old)

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DeveloperGuidelines