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[wiki:S3] | [wiki:S3XRC/RESTfulAPI S3 RESTful API] | s3_rest_controller
= s3_rest_controller =

== Introduction ==

The so-called '''REST Controller''' (function {{{s3_rest_controller()}}}) is a helper function to easily apply the RESTful API of the [wiki:S3XRC/RESTfulAPI/S3Resource S3Resource] class to your controller.

{{{s3_rest_controller}}} does:

  - parse and execute the incoming HTTP request on the specified resource
  - populate and hand-over view variables
  - choose and set the response view template ({{{response.view}}})

Using {{{s3_rest_controller}}}, a basic RESTful controller for the {{{pr_image}}} table can look like:

{{{
def image():

    """ RESTful CRUD controller """

    return s3_rest_controller("pr", "image")

}}}

This exposes all standard [wiki:S3XRC/RESTfulAPI/URLFormat URLs] and [wiki:S3XRC/RESTfulAPI methods] for this table, including:

  - interactive create, read, update, delete and list views
  - non-interactive data export/import (GET/POST/PUT/DELETE) in multiple formats

== Basic Syntax ==

{{{
output = s3_rest_controller(prefix, resourcename)
}}}

  - '''prefix''' is the application prefix of the resource
  - '''resourcename''' is the name of the resource (without prefix)

  - '''output''' contains the result of the request and can be returned from the controller as-is
    - in interactive view formats, this is a {{{dict}}} of view variables

== Basic Options ==

All of the following options are set using:

{{{
s3mgr.configure(table, key=value)
}}}

where:
  - '''table''' is the respective DB table
  - '''key''' is the setting key
  - '''value''' is the configuration value

You can specify multiple settings at once:
{{{
s3mgr.configure(table, key1=value1, key2=value2, ...)
}}}

'''configure''' overrides any settings that have been made for that table before (e.g. in the model), where only the specified keys are changed while all others are left untouched.

You can also delete a particular setting by:

{{{
s3mgr.model.clear_config(table, "key")
}}}

where "key" must be the respective key as ''string''.

=== CRUD Options ===

You can define which of the CRUD functions are allowed for your resource. By default, they all are True.

{{{
  s3mgr.configure(table, editable=True,             # Records can be updated
                         insertable=True,           # New records can be added
                         deletable=True,            # Records can be deleted
                         listadd=True)              # to have a add-record form in list view
}}}

Note:
  - these settings are completely independent from the user's permission to perform the respective actions. If you have set {{{insertable=False}}}, then adding records to this table will be impossible even if the user has the permission to add records.
  - in standard views, the add-form in list views is hidden and can be activated by clicking the respective "Add Record" button. If {{{listadd=False}}}, then the "Add Record" button will redirect to the create-form view instead.
  - these settings do not affect non-interactive representations

=== List-Fields ===

By default, all readable fields of a table appear in list views.

To control which fields are to be included in list views, to include virtual fields or fields in referenced tables, or to change the order of the columns, use the {{{list_fields}}} CRUD setting.

This setting takes a list of field names of the fields to be displayed:

{{{
s3mgr.configure(table,
                list_fields=["id", "name", "location_id"])
}}}

  NOTE: If your view uses dataTables (which all default view templates do), then you '''must''' include {{{"id"}}} at the first place to have it working properly.

For virtual fields, you should provide a tuple of {{{(T("FieldLabel"), "fieldname")}}}, because virtual fields do not have a {{{.label}}} setting (as they are functions and not {{{Field}}} instances):

{{{
s3mgr.configure(table,
                list_fields=["id",
                             "name",
                             "location_id",
                             (T("Total costs"), "total_costs")]
}}}

You can use the tuple notation for any other field as well, in order to override the field label for this list view.

To include a field from a referenced table, insert the field name as "<foreign_key>$<fieldname>", e.g.:

{{{
s3mgr.configure(table,
                list_fields=["id",
                             "name",
                             "location_id$lat",
                             "location_id$lon"]
}}}

=== List-add ===

By default, list views will contain a hidden create-form and an "Add Record"-button to activate the create-form (provided that the user is authorized to add records to this resource).

If the resource is set to {{{insertable=False}}} or if the user is not permitted to create records in this table, no "Add Record"-button will be available.

  NOTE: ''If for some reason the default embedded create-form is not desired, you can set {{{s3xrc.configure(table, listadd=False, addbtn=True)}}}, which will render the "Add Record"-button as link to the create method instead.''
=== Redirection ===

Default destination of the redirection after a ''create'' or ''update'' is the ''read'' view of the processed record, after a ''delete'' it is the ''list'' view of the respective table.

The redirection destination can be configured per DB table, using:

{{{
s3mgr.configure(table, create_next=url)
}}}
{{{
s3mgr.configure(table, update_next=url)
}}}
{{{
s3mgr.configure(table, delete_next=url)
}}}

where:
  - '''table''' is the respective DB table
  - '''url''' is the URL to redirect to

If, for create_next or update_next, '''url''' contains the string "[id]" (or its URL-encoded equivalent), then this string will be replaced by the ID of the updated/newly created record before redirection.

Note:
  - redirection does not happen after non-interactive data imports!
=== Callbacks ===

For every DB table, you can define functions to be invoked upon certain CRUD events. Those "callbacks" can be:

  - a single callable (function, lambda, callable object)
  - a list of callables, which are invoked in list order
  - a dict of callables, where the tablename is used as key to find the callable to be invoked
  - a dict of lists of callables, where the tablename is used as key to find the list of callables to be executed in list order

The return value of the callables, if any, is ignored.

  '''Important:''' Callbacks are invoked in the same manner during non-interactive data imports, where usually multiple records will be processed in the same request. Therefore, callback functions '''must not''' redirect, nor commit or roll back the current transaction!
==== Validation Callbacks ====

You can define extra form validation methods to be invoked after a create/update form has successfully passed the indivdual field validation, by using:

{{{
s3db.configure(tablename, create_onvalidation=callback)
}}}
{{{
s3db.configure(tablename, update_onvalidation=callback)
}}}

where:

  - '''table''' is the respective DB table
  - '''callable''' is the callback setting, see [#Callbacks Callbacks]

If either of {{{create_onvalidation}}} or {{{update_onvalidation}}} is not set, then the {{{onvalidation}}} setting is tried:

{{{
s3db.configure(tablename, onvalidation=callback)
}}}

This allows you to define a common onvalidation callback for both ''create'' and ''update''.

Onvalidation callbacks are meant to allow additional form data validation (beyond individual field validators). The callback functions receive the '''form''' as first and only parameter, while their return values will be ignored.

Any validation errors are to be reported directly into the form as:
{{{
form.errors[fieldname] = error_msg
}}}

where:

  - '''fieldname''' is the field containing the invalid value
  - '''error_msg''' is the error message to be displayed in the form close to that field

If after the execution of the onvalidation callback any messages are found in {{{form.errors}}}, then no data are being imported and instead, the process will return to the input view with the messages displayed close to the respective form fields.

In non-interactive data imports, the error message will be added to the import tree as extra attribute of the invalid element. The XML importer will however process all records in the import tree in order to find all validation errors before reporting the invalid tree to the sender, and in case {{{ignore_errors}}} is used, all valid records will be imported in the first attempt.

==== On-accept Callbacks ====

You can define methods to be invoked after a record has been created/updated, by using:

{{{
s3db.configure(tablename, create_onaccept=callback)
}}}
{{{
s3db.configure(tablename, update_onaccept=callback)
}}}

where:

  - '''table''' is the respective DB table
  - '''callable''' is the callback setting, see [#Callbacks Callbacks]

If either of {{{create_onaccept}}} or {{{update_onaccept}}} is not set, then the {{{onaccept}}} setting is tried:

{{{
s3db.configure(tablename, onaccept=callback)
}}}

This allows you to define a common onaccept callback for both ''create'' and ''update''.

The {{{onaccept}}} callbacks are meant to perform extra post-processing of the newly created/updated record (e.g. to update dependent records). The callback functions receive the respective {{{FORM}}} instance (with the input data being in {{{form.vars}}}) as first and only parameter, while their return value will be ignored.

==== On-Delete-Cascade Callback ====

You can specify callbacks to be invoked when a record is to be deleted:

{{{
s3db.configure(tablename, ondelete_cascade=callback)
}}}

where:

  - '''table''' is the respective DB table
  - '''callable''' is the callback setting, see [#Callbacks Callbacks]

The {{{ondelete_cascade}}} callback is meant to perform cascade actions ''before'' deleting a record (e.g. to update or remove dependend records, or to release constraints that cannot be introspected using the "ondelete" field setting). The hook will receive the ''record'' as its only parameter, its return value will be ignored.

  '''Note:''' the ''record'' will only contain the record ID but no details

==== On-Delete Callback ====

You can also define callbacks to be invoked ''after'' a record has been deleted:

{{{
s3db.configure(tablename, ondelete=callback)
}}}

where:

  - '''table''' is the respective DB table
  - '''callable''' is the callback setting, see [#Callbacks Callbacks]

The {{{ondelete}}} callbacks are meant to perform extra post-processing of the deleted record (e.g. updates to counters or other aggregates). The callback function will receive the respective ''record'' as its only parameter, while its return value will be ignored.

  '''Note:''' at the time when the callback is invoked, the record is already deleted from the database.

  '''Note:''' the ''record'' will only contain the record ID but no details

  '''Note:''' ''soft-''deleted (archived) records hold their former foreign keys as a JSON object in the {{{deleted_fk}}} field, whilst all foreign key fields will be set to None.

  '''Important:''' Do not delete a record by simply settings its {{{deleted}}} field to True. This would neither perform the necessary cascading, nor invoke any callbacks nor does it properly store and release any foreign key constraints. Always use S3Resource.delete() to delete records!
=== Pagination ===

The default pagination method is '''server-side''' (SSPag), meaning, in list views the client will receive only the first of the available rows, and then retrieve more rows as needed by subsequent Ajax calls.

In contrast to that, in '''client-side''' pagination (CSPag) mode all available rows of the list are retrieved and send to the client at once. For most tables, though, this will probably be a huge data set and take a long time to extract and transmit, while mostly being unnecessary when the user only needs to see the first 20 rows to find what he's looking for.

However, some tables may by their nature only contain one or few rows, and then server-side pagination is not needed (in fact, inefficient). In these cases, the respective controller can turn it off by:

{{{
response.s3.no_sspag=True
}}}

== View Control ==

In web2py, the default view is chosen after the name of the controller, i.e. if the controller is person(), then the default view is person.html.

s3_rest_controller() modifies this schema in order to allow you to create method-specific views for the same controller.
=== Default View ===

The default view is chosen in a fallback cascade, which is:

  1. <prefix>/<resource-name>_<component-name>_<method>.html
  2. <prefix>/<resource-name>_<method>.html
  3. <method>.html

where:

  - '''prefix''' is the application prefix of the resource name (e.g. "pr")
  - '''resource-name''' is the name of the resource (e.g. "person")
  - '''component-name''' is the name of the component resource (e.g. "address", only if the request targets a component resource)
  - '''method''' is one of:
    - display
    - list
    - list_create (to be deprecated)
    - create
    - update
    - delete
    - search

Example:

{{{
http://localhost:8000/eden/pr/person/create.html
}}}

is looking for one of '''pr/person_create.html'', '''pr/create.html'' or finally ''create.html'' as default view.

If none of these is found, "default.html" serves as catch-all fallback.
=== Custom View ===

To choose a custom view, you can easily override the default setting ''after'' s3_rest_controller returns:

{{{
  output = s3_rest_controller(prefix, resourcename)

  response.view = "myview.html"

  return output
}}}
=== Additional View Variables ===

In interactive view formats, any additional named arguments in the {{{s3_rest_controller}}} argument list will be added to the view variables:

{{{
output = s3_rest_controller(prefix, resourcename, **attr)
}}}

  - '''**attr''': additional view variables


  - any callable argument will be invoked with the {{{S3Request}}} as first and only argument, and its return value will be added to the view variables
  - any non-callable argument will be added to the view variables as-is
  - any argument that gives {{{None}}} will remove this key from the view variables

A typical use-case is '''rheader''':

{{{
def my_rheader(r):
  if r.interactive and r.component:
    # Code producing the rheader...
    return rheader
  else:
    return None

output = s3_rest_controller(prefix, name, rheader=my_rheader)
}}}

If {{{my_rheader(r)}}} gives something else than {{{None}}}, then this value is added as {{{rheader}}} to the view variables.

== Advanced Options ==

=== Filtering Lists ===

You can filter lists in the controller by setting {{{response.s3.filter}}} to a filter query:
{{{
    # This filters for females:
    response.s3.filter = (db.pr_person.gender == 2)

    return s3_rest_controller("pr", "person")
}}}

Note that this only takes effect in the main controller (not in prep or postp).

Note that {{{response.s3.filter}}} affects both, the primary resource and components!

In {{{prep}}}, you can also add filter queries using the {{{add_filter}}} method:
{{{
    def prep(r):
        resource = r.resource
        query = (db.pr_address.type == 1) # Home addresses only
        resource.add_filter(query)
        return True
    response.s3.prep = prep

    return s3_rest_controller("pr", "person")
}}}

However, {{{add_filter}}} again affects both, primary and component records - so this example would:
- only retrieve {{{person}}} records which have a type 1 {{{address}}} record
- only retrieve the {{{address}}} records with type 1.

This can be an unwanted side-effect.

To have the primary resource unfiltered, and filter only records in a particular component, you can use {{{add_component_filter}}}:
{{{
    def prep(r):
        resource = r.resource
        query = (db.pr_address.type == 1) # Home addresses only
        resource.add_component_filter("address", query)
        return True
    response.s3.prep = prep

    return s3_rest_controller("pr", "person")
}}}

In this case, all {{{person}}} records would be selected - while only {{{address}}} records of type 1 would be retrieved.
=== Pre-populating Create-Forms ===

Create-forms can be pre-populated with data by one of these 3 methods:

  1. model defaults (standard)
  2. values from another record in the database
  3. values provided by the controller

'''Model defaults''' are defined per field and can be set as {{{db.my_table.field.default = value}}} at any time before the REST method is applied (even in the pre-process).

'''Values from another record''' in the database can be used via a URL query like:

  - /my/resource/create?from_record=''id''&from_fields=''fieldname1'',''fieldname2'',...

The ''id'' of the original record can also be specified as ''tablename.id'', if the original record is in another table. Additionally, fieldnames can be specified as ''fieldname$original_fieldname'' to map between different fieldnames.

To '''pre-populate''' Create-forms '''from the controller''', you can specify the variable {{{populate}}} in the arguments of {{{s3_rest_controller}}}:

{{{
output = s3_rest_controller(prefix, resourcename,
                            populate=dict(fieldname1=value1,
                                          fieldname2=value2))
return output
}}}

Instead of a {{{dict}}}, you can also pass a callable object as {{{populate}}}. This will be executed with the current {{{S3Request}}} and the named arguments of {{{s3_rest_controller}}} in order to produce the field/value {{{dict}}}:

{{{
def populate(r, **attr):
    """
    Helper function to pre-populate create-forms

    """

    # some code to produce the data
    # ...

    # return the dict
    return dict(fieldname1=value1,
                fieldname2=value2)

output = s3_rest_controller(prefix, resourcename,
                            populate=populate)

return output
}}}

Note that {{{populate}}} will only be applied in {{{GET}}} requests and only if no record_id is specified. That means, if it uses a separate form to generate the data, you need to revert the request into {{{GET}}} in order to have the create-form pre-populated:

{{{
data = None
form = FORM(...some form...)
output = dict(helper_form=form)
if form.accepts(request.vars, session, formname="helper_form"):
    output = dict() # remove the helper form
    data = Storage(...) # some code to extract the data from the helper form
if data:
    request.env.request_method = "GET" # revert to GET if data available

_output = s3_rest_controller(prefix, resourcename, populate=data)

if isinstance(_output, dict):
    output.update(_output)
else:
    output = _output

return output
}}}

NB: This construction could be used e.g. to loop in an OCR client into a REST controller. The helper form would then be a file upload form which is displayed alongside with the normal create-form - so the user can either enter data manually and submit the create-form, or first submit a file to pre-populate the create form, and then edit the data and submit the create-form.
=== Pre-Process ===

  - ''coming soon...''

==== Passing information between main controller & pre-processor ====

Scope normally means that these 2 sections can only talk to each other via globals or the Request object.

If you need to pass data between them, you can use this trick:
{{{
vars = {} # the surrounding dict
def prep(r, vars):
    vars.update(x=y) # the actual variable to pass is x
    return True

response.s3.prep = lambda r, vars=vars: prep(r, vars)

output = shn_rest_controller(module, resource)

x = vars.get(x, None)
}}}

An example usage is in {{{controllers/gis.py}}} for location()
=== Post-Process ===

=== Method Handlers ===

=== Custom Methods ===

----

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