QWeb is the primary templating engine used by Odoo2. It is an XML templating engine1 and used mostly to generate HTML fragments and pages.
Template directives are specified as XML attributes prefixed with t-
,
for instance t-if
for conditionals, with elements
and other attributes being rendered directly.
To avoid element rendering, a placeholder element <t>
is also available,
which executes its directive but doesn't generate any output in and of
itself:
<t t-if="condition">
<p>Test</p>
</t>
will result in:
<p>Test</p>
if condition
is true, but:
<div t-if="condition">
<p>Test</p>
</div>
will result in:
<div>
<p>Test</p>
</div>
data output
QWeb has a primary output directive which automatically HTML-escape its
content limiting XSS risks when displaying user-provided content: esc
.
esc
takes an expression, evaluates it and prints the content:
<p><t t-esc="value"/></p>
rendered with the value value
set to 42
yields:
<p>42</p>
There is one other output directive raw
which behaves the same as
respectively esc
but does not HTML-escape its output. It can be useful
to display separately constructed markup (e.g. from functions) or already
sanitized user-provided markup.
conditionals
QWeb has a conditional directive if
, which evaluates an expression given
as attribute value:
<div>
<t t-if="condition">
<p>ok</p>
</t>
</div>
The element is rendered if the condition is true:
<div>
<p>ok</p>
</div>
but if the condition is false it is removed from the result:
<div>
</div>
The conditional rendering applies to the bearer of the directive, which does
not have to be <t>
:
<div>
<p t-if="condition">ok</p>
</div>
will give the same results as the previous example.
Extra conditional branching directives t-elif
and t-else
are also
available:
<div>
<p t-if="user.birthday == today()">Happy bithday!</p>
<p t-elif="user.login == 'root'">Welcome master!</p>
<p t-else="">Welcome!</p>
</div>
loops
QWeb has an iteration directive foreach
which take an expression returning
the collection to iterate on, and a second parameter t-as
providing the
name to use for the "current item" of the iteration:
<t t-foreach="[1, 2, 3]" t-as="i">
<p><t t-esc="i"/></p>
</t>
will be rendered as:
<p>1</p>
<p>2</p>
<p>3</p>
Like conditions, foreach
applies to the element bearing the directive's
attribute, and
<p t-foreach="[1, 2, 3]" t-as="i">
<t t-esc="i"/>
</p>
is equivalent to the previous example.
foreach
can iterate on an array (the current item will be the current
value), a mapping (the current item will be the current key) or an integer
(equivalent to iterating on an array between 0 inclusive and the provided
integer exclusive).
In addition to the name passed via t-as
, foreach
provides a few other
variables for various data points:
Warning
$as
will be replaced by the name passed to t-as
$as_all
- the object being iterated over
$as_value
- the current iteration value, identical to
$as
for lists and integers, but for mappings it provides the value (where$as
provides the key) $as_index
- the current iteration index (the first item of the iteration has index 0)
$as_size
- the size of the collection if it is available
$as_first
- whether the current item is the first of the iteration (equivalent to
$as_index == 0
) $as_last
- whether the current item is the last of the iteration (equivalent to
$as_index + 1 == $as_size
), requires the iteratee's size be available $as_parity
- either
"even"
or"odd"
, the parity of the current iteration round $as_even
- a boolean flag indicating that the current iteration round is on an even index
$as_odd
- a boolean flag indicating that the current iteration round is on an odd index
These extra variables provided and all new variables created into the
foreach
are only available in the scope of the``foreach``. If the
variable exists outside the context of the foreach
, the value is copied
at the end of the foreach into the global context.
<t t-set="existing_variable" t-value="False"/>
<!-- existing_variable now False -->
<p t-foreach="[1, 2, 3]" t-as="i">
<t t-set="existing_variable" t-value="True"/>
<t t-set="new_variable" t-value="True"/>
<!-- existing_variable and new_variable now True -->
</p>
<!-- existing_variable always True -->
<!-- new_variable undefined -->
attributes
QWeb can compute attributes on-the-fly and set the result of the computation
on the output node. This is done via the t-att
(attribute) directive which
exists in 3 different forms:
t-att-$name
an attribute called
$name
is created, the attribute value is evaluated and the result is set as the attribute's value:<div t-att-a="42"/>
will be rendered as:
<div a="42"></div>
t-attf-$name
same as previous, but the parameter is a format string instead of just an expression, often useful to mix literal and non-literal string (e.g. classes):
<t t-foreach="[1, 2, 3]" t-as="item"> <li t-attf-class="row {{ item_parity }}"><t t-esc="item"/></li> </t>
will be rendered as:
<li class="row even">1</li> <li class="row odd">2</li> <li class="row even">3</li>
t-att=mapping
if the parameter is a mapping, each (key, value) pair generates a new attribute and its value:
<div t-att="{'a': 1, 'b': 2}"/>
will be rendered as:
<div a="1" b="2"></div>
t-att=pair
if the parameter is a pair (tuple or array of 2 element), the first item of the pair is the name of the attribute and the second item is the value:
<div t-att="['a', 'b']"/>
will be rendered as:
<div a="b"></div>
setting variables
QWeb allows creating variables from within the template, to memoize a computation (to use it multiple times), give a piece of data a clearer name, ...
This is done via the set
directive, which takes the name of the variable
to create. The value to set can be provided in two ways:
a
t-value
attribute containing an expression, and the result of its evaluation will be set:<t t-set="foo" t-value="2 + 1"/> <t t-esc="foo"/>
will print
3
if there is no
t-value
attribute, the node's body is rendered and set as the variable's value:<t t-set="foo"> <li>ok</li> </t> <t t-esc="foo"/>
will generate
<li>ok</li>
(the content is escaped as we used theesc
directive)Note
using the result of this operation is a significant use-case for the
raw
directive.
calling sub-templates
QWeb templates can be used for top-level rendering, but they can also be used
from within another template (to avoid duplication or give names to parts of
templates) using the t-call
directive:
<t t-call="other-template"/>
This calls the named template with the execution context of the parent, if
other_template
is defined as:
<p><t t-value="var"/></p>
the call above will be rendered as <p/>
(no content), but:
<t t-set="var" t-value="1"/>
<t t-call="other-template"/>
will be rendered as <p>1</p>
.
However this has the problem of being visible from outside the t-call
.
Alternatively, content set in the body of the call
directive will be
evaluated before calling the sub-template, and can alter a local context:
<t t-call="other-template">
<t t-set="var" t-value="1"/>
</t>
<!-- "var" does not exist here -->
The body of the call
directive can be arbitrarily complex (not just
set
directives), and its rendered form will be available within the called
template as a magical 0
variable:
<div>
This template was called with content:
<t t-raw="0"/>
</div>
being called thus:
<t t-call="other-template">
<em>content</em>
</t>
will result in:
<div>
This template was called with content:
<em>content</em>
</div>
Python
Exclusive directives
asset bundles
"smart records" fields formatting
The t-field
directive can only be used when performing field access
(a.b
) on a "smart" record (result of the browse
method). It is able
to automatically format based on field type, and is integrated in the
website's rich text edition.
t-options
can be used to customize fields, the most common option
is widget
, other options are field- or widget-dependent.
debugging
t-debug
invokes a debugger using PDB's
set_trace
API. The parameter should be the name of a module, on which aset_trace
method is called:<t t-debug="pdb"/>
is equivalent to
importlib.import_module("pdb").set_trace()
Helpers
Request-based
Most Python-side uses of QWeb are in controllers (and during HTTP requests),
in which case templates stored in the database (as
views) can be trivially rendered by calling
odoo.http.HttpRequest.render()
:
response = http.request.render('my-template', {
'context_value': 42
})
This automatically creates a Response
object which can
be returned from the controller (or further customized to suit).
View-based
At a deeper level than the previous helper is the render
method on
ir.ui.view
:
render(cr, uid, id[, values][, engine='ir.qweb][, context])
Renders a QWeb view/template by database id or external id.
Templates are automatically loaded from ir.ui.view
records.
Sets up a number of default values in the rendering context:
request
- the current
WebRequest
object, if any debug
- whether the current request (if any) is in
debug
mode quote_plus
- url-encoding utility function
json
- the corresponding standard library module
time
- the corresponding standard library module
datetime
- the corresponding standard library module
- relativedelta
- see module
keep_query
- the
keep_query
helper function
- values -- context values to pass to QWeb for rendering
- engine (
str
) -- name of the Odoo model to use for rendering, can be used to expand or customize QWeb locally (by creating a "new" qweb based onir.qweb
with alterations)
Javascript
Exclusive directives
defining templates
The t-name
directive can only be placed at the top-level of a template
file (direct children to the document root):
<templates>
<t t-name="template-name">
<!-- template code -->
</t>
</templates>
It takes no other parameter, but can be used with a <t>
element or any
other. With a <t>
element, the <t>
should have a single child.
The template name is an arbitrary string, although when multiple templates are related (e.g. called sub-templates) it is customary to use dot-separated names to indicate hierarchical relationships.
template inheritance
Template inheritance is used to alter existing templates in-place, e.g. to add information to templates created by an other modules.
Template inheritance is performed via the t-extend
directive which takes
the name of the template to alter as parameter.
The alteration is then performed with any number of t-jquery
sub-directives:
<t t-extend="base.template">
<t t-jquery="ul" t-operation="append">
<li>new element</li>
</t>
</t>
The t-jquery
directives takes a CSS selector. This selector is used
on the extended template to select context nodes to which the specified
t-operation
is applied:
append
- the node's body is appended at the end of the context node (after the context node's last child)
prepend
- the node's body is prepended to the context node (inserted before the context node's first child)
before
- the node's body is inserted right before the context node
after
- the node's body is inserted right after the context node
inner
- the node's body replaces the context node's children
replace
- the node's body is used to replace the context node itself
- No operation
if no
t-operation
is specified, the template body is interpreted as javascript code and executed with the context node asthis
Warning
while much more powerful than other operations, this mode is also much harder to debug and maintain, it is recommended to avoid it
debugging
The javascript QWeb implementation provides a few debugging hooks:
t-log
takes an expression parameter, evaluates the expression during rendering and logs its result with
console.log
:<t t-set="foo" t-value="42"/> <t t-log="foo"/>
will print
42
to the consolet-debug
triggers a debugger breakpoint during template rendering:
<t t-if="a_test"> <t t-debug=""> </t>
will stop execution if debugging is active (exact condition depend on the browser and its development tools)
t-js
the node's body is javascript code executed during template rendering. Takes a
context
parameter, which is the name under which the rendering context will be available in thet-js
's body:<t t-set="foo" t-value="42"/> <t t-js="ctx"> console.log("Foo is", ctx.foo); </t>
Helpers
core.qweb
(core is the web.core
module) An instance of QWeb2.Engine()
with all module-defined template
files loaded, and references to standard helper objects _
(underscore), _t
(translation function) and JSON.
core.qweb.render
can be used to
easily render basic module templates
API
class QWeb2.Engine()
The QWeb "renderer", handles most of QWeb's logic (loading, parsing, compiling and rendering templates).
OpenERP Web instantiates one for the user in the core module, and
exports it to core.qweb
. It also loads all the template files
of the various modules into that QWeb instance.
A QWeb2.Engine()
also serves as a "template namespace".
QWeb2.Engine.render(template[, context])
Renders a previously loaded template to a String, using
context
(if provided) to find the variables accessed
during template rendering (e.g. strings to display).
- template (
String
) -- the name of the template to render - context (
Object
) -- the basic namespace to use for template rendering
The engine exposes an other method which may be useful in some
cases (e.g. if you need a separate template namespace with, in
OpenERP Web, Kanban views get their own QWeb2.Engine()
instance so their templates don't collide with more general
"module" templates):
QWeb2.Engine.add_template(templates)
Loads a template file (a collection of templates) in the QWeb instance. The templates can be specified as:
- An XML string
- QWeb will attempt to parse it to an XML document then load it.
- A URL
- QWeb will attempt to download the URL content, then load the resulting XML string.
- A
Document
orNode
- QWeb will traverse the first level of the document (the child nodes of the provided root) and load any named template or template override.
A QWeb2.Engine()
also exposes various attributes for
behavior customization:
QWeb2.Engine.prefix
Prefix used to recognize directives during parsing. A string. By
default, t
.
QWeb2.Engine.debug
Boolean flag putting the engine in "debug mode". Normally, QWeb intercepts any error raised during template execution. In debug mode, it leaves all exceptions go through without intercepting them.
QWeb2.Engine.jQuery
The jQuery instance used during template inheritance processing.
Defaults to window.jQuery
.
QWeb2.Engine.preprocess_node
A Function
. If present, called before compiling each DOM
node to template code. In OpenERP Web, this is used to
automatically translate text content and some attributes in
templates. Defaults to null
.