Support for repeated sections
GvaScript.Repeat - Support for repeated sections
<div repeat="foo"> <h2>Foo #{foo.count}</h2> This is the repeated foo section <table> <tr repeat="bar"> <td>Item #{bar.count}</td> <td><input name="#{bar.path}.buz"></td> <td><button onclick="GvaScript.Repeat.remove('#{bar.path}')"> Remove this row </button></td> </tr> </table> <button onclick="GvaScript.Repeat.add('#{foo.path}.bar')"> Add a bar </button> </div> <button onclick="GvaScript.Repeat.add('foo')">Add a foo</button> <script> GvaScript.Repeat.init(document.body); </script
This module of Alien::GvaScript implements a mechanism for repeated elements within an HTML page. The main use is within forms, for dynamic expansion of subforms, so it is quite likely that you will want to use the Alien::GvaScript::Form API instead of calling the present module directly. However, the repeat mechanism will work for any kind of HTML element.
The design is partially inspired by the Web Forms 2.0
proposal
(http://www.whatwg.org/specs/web-forms/current-work/), but is
not an attempt to implement the proposed specification: there are
some differences both in syntax and in semantics.
At initialization stage, the DOM is inspected for finding
repeat elements (elements having a repeat
attribute).
These elements are removed from the DOM and replaced
by placeholders (empty DOM elements, just marking where
the repetition blocks should be inserted).
Each placeholder stores a template, which is
a plain string representation of the repeat element, with
special markup for template instanciation.
The template may then be dynamically instanciated into
repetition blocks by calling the /add method.
<div repeat="foo" repeat-start="3" repeat-min="2" repeat-max="6" repeat-prefix=""> <!-- content to be repeated, using #{foo.ix}, #{foo.path}, etc. --> </div>
Any element marked with a non-empty repeat
attribute is
a repeat element; the value of that attribute defines
the repeat name. Repeat elements can be nested, and their
repeat names are used to distinguish at which level a repetition
block should be instanciated.
Other attributes of the repetion model all start with
the repeat
prefix, as listed below; these attributes are optional.
marks the element as a repeat element, and defines the repeat name.
defines how many repetition blocks should be automatically created as initialization time. Default is 1.
minimum number of repetition blocks. Prevents deletion of repetition blocks under that number. Default is 0.
maximum number of repetition blocks. Prevents addition of repetition blocks over that number. Default is 99.
defines the initial fragment of the repeat path
(see
explanation below). Only valid for top-level repetition elements,
because nested repetition elements are automatically prefixed
by their parent repetition element. Default is the empty string.
The content of a repeat element may contain special markup for repetition variables, which will be replaced by values when the element is instanciated into a repetition block.
Variables are written #{<repetition name>.<variable>}
, like for
example #{foo.ix}
, #{foo.count}
or #{bar.path}
. The
repetition name is the value of the repeat
attribute of the repeat
element, as explained above; in this namespace, the following
variables are defined
current number of repetition blocks for that repeat element, starting at 1.
integer index of the current repetition block, starting at 0.
cumulated list of repetition name and repetition indices, separated by dots.
value of the repeat-min
attribute.
value of the repeat-max
attribute.
The path
is unique within any nesting of repeat elements,
and therefore is typically used for ids or for
names of input elements :
<tr repeat="bar"> <td>Item #{bar.count}</td> <td><input name="#{bar.path}.buz"></td> </tr>
Within the 3rd repetition block of bar
, nested
within the 2nd repetition block of foo
, the value of
#{bar.path}
will be foo.2.bar.3
and therefore
in this example the input name would be
foo.2.bar.3.buz
.
Implementation note: the #{...}
syntax for
variables is borrowed from prototype.js
's Template
class; however, the implementation of substitutions
is done in plain javascript, without calling
Template.evaluate()
method.
GvaScript.Repeat.init(element)
Walks down the DOM under the given element, finds all
elements having a repeat
attribute, replaces these
by placeholders.
The element
argument will be fed to prototype.js
's
$()
function, so it can be either a DOM element or
an id string.
GvaScript.Repeat.add(repeat_name, count)
Creates one or several new repetition blocks in the DOM,
after the current blocks, by instanciating
the repeat element repeat_name
(including prefix).
The count
argument is optional and states how many blocks
should be added; default is 1. Returns the final number of
repetition blocks for that repeat element.
If the repeat structure looks like
<div repeat="foo" repeat-prefix="top"> <div repeat="bar">
then a new foo
repetition block is instanciated
through add('top.foo')
, and a new bar
repetition
block is instanciated through add('#{foo.path}.bar')
.
GvaScript.Repeat.remove(repetition_block)
Removes a repetition block from the DOM. The argument is either a DOM element or a string containing the element id.
All repetition blocks above the removed block are renumbered, leaving no hole in the index sequence. To do so, these blocks are also removed from the DOM, and then added again through the /add method.
If the repetition block is within a form, you probably want to call Alien::GvaScript::Form/remove instead of the present method, in order to properly preserve current form data.
For a general explanation on registering handlers for GvaScript events, see the event documentation.
<div repeat="Foo" onRemove="alert(event.target.id + ' is removed')">
This event is triggered whenever a repetition block is removed through the /remove method. Since this method also removes all repetition blocks above the requested block, the event will be triggered once for each block.
Alien::GvaScript