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Hardik Juneja
jio-main
Commits
c0381741
Commit
c0381741
authored
Dec 30, 2013
by
Marco Mariani
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docs: explain custom operators; default_match -> equal_match
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252a08a0
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docs/keys.rst
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c0381741
...
...
@@ -17,9 +17,10 @@ Let's start with a simple search:
}
Each of the ``.someproperty`` attribute in objects' metadata is compared with
``comparison_value`` through a function defined by the '=' operator.
``comparison_value`` through a function defined by the '=' operator. Normally,
it would be a string match that uses the wildcard_character, if present.
Such comparison functions (=, !=, <...) are predefined in jIO, but you can provide your own
:
You can provide your own function to be used as '=' operator
:
.. code-block:: javascript
...
...
@@ -32,14 +33,13 @@ Such comparison functions (=, !=, <...) are predefined in jIO, but you can provi
type: 'simple',
key: {
read_from: 'someproperty',
default
_match: strictEqual
equal
_match: strictEqual
},
value: comparison_value
}
Note: ``default_match`` will only be used if no ``operator`` is specified.
You may decide to interpret the ``wildcard_character`` or just ignore it, as in this case.
Inside ``equal_match``, you can decide to interpret the ``wildcard_character``
or just ignore it, as in this case.
If you need to convert or preprocess the values before comparison, you can provide
a conversion function:
...
...
@@ -60,8 +60,8 @@ a conversion function:
}
In this case, the operator is still the default '='.
You can combine ``cast_to`` and ``
default
_match``:
In this case, the operator is still the default '='
that works with strings
.
You can combine ``cast_to`` and ``
equal
_match``:
.. code-block:: javascript
...
...
@@ -70,7 +70,7 @@ You can combine ``cast_to`` and ``default_match``:
key: {
read_from: 'someproperty',
cast_to: numberType,
default
_match: strictEqual
equal
_match: strictEqual
},
value: comparison_value
}
...
...
@@ -115,12 +115,80 @@ from any string:
return s;
};
...
cast_to: accentFold
...
A more robust solution to manage diacritics is recommended for production
environments, with unicode normalization, like (untested):
https://github.com/walling/unorm/
Overriding operators and sorting
--------------------------------
The advantage of providing an ``equal_match`` function is that it can work with basic types;
you can keep the values as strings or, if you use a ``cast_to`` function, it can return strings,
numbers, arrays... and that's fine if all you need is the '=' operator.
It's also possible to customize the behavior of the other operators: <, >, !=...
To do that, the object returned by ``cast_to`` must contain a ``.cmp``
property, that behaves like the ``compareFunction`` described in
`Array.prototype.sort() <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort>`_:
.. code-block:: javascript
function myType (...) {
...
return {
...
'cmp': function (b) {
if (a < b) {
return -1;
}
if (a > b) {
return +1;
}
return 0;
}
};
}
...
cast_to: myType
...
If the < or > comparison makes no sense for the objects, the function should return ``undefined``.
The ``.cmp()`` property is also used, if present, by the sorting feature of complex queries.
Partial Date/Time match
-----------------------
As a real life example, consider a list of documents that have a *start_task* property.
The value of ``start_task`` can be an `ISO 8601 <http://en.wikipedia.org/wiki/ISO_8601>`_ string
with date and time information including fractions of a second. Which is, honestly, a bit too
much for most queries.
By using a ``cast_to`` function with custom operators, it is possible to perform queries like
"start_task > 2010-06", or "start_task != 2011". Partial time can be used as well, so
we can ask for projects started after noon of a given day: ``start_task = "2011-04-05" AND start_task > "2011-04-05 12"``
The JIODate type has been implemented on top of the `Moment.js <http://momentjs.com/>`_ library, which
has a rich API with support for multiple languages and timezones. No special support for timezones
is present (yet) in JIODate.
To use JIODate, include the ``jiodate.js`` and ``moment.js`` files in your
application, then set ``cast_to = jiodate.JIODate``.
Key Schemas
-----------
...
...
@@ -135,12 +203,12 @@ you can group all of them in a schema object for reuse:
date_day: {
read_from: 'date',
cast_to: 'dateType',
default
_match: 'sameDay'
equal
_match: 'sameDay'
},
date_month: {
read_from: 'date',
cast_to: 'dateType',
default
_match: 'sameMonth'
equal
_match: 'sameMonth'
}
},
cast_lookup: {
...
...
@@ -184,12 +252,12 @@ A key_schema object can have three properties:
then cast_to must be a function.
* ``match_lookup`` - optional, a mapping of name: function that will
be used if
default_match
is a string. If match_lookup is not provided,
then
default_match
must be a function.
be used if
``equal_match``
is a string. If match_lookup is not provided,
then
``equal_match``
must be a function.
Using a schema
^^^^^^^^^^^^^^
--------------
A schema can be used:
...
...
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