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Commite9a81bf

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[#3044] Furthering@wouterj's work on the ExpressionLanguage component
This adds more examples, details about how to pass in variables, and working with objects/arrays
1 parent70b475b commite9a81bf

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‎components/expression_language/introduction.rst

Lines changed: 62 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -10,24 +10,51 @@ The ExpressionLanguage Component
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(mostly, but not limited to, Booleans).
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..versionadded::2.4
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The ExpressionLanguage component wasnew in Symfony 2.4.
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The ExpressionLanguage component wasadded in Symfony 2.4.
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Installation
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------------
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You can install the component in 2 different ways:
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* Use the official Git repository (https://github.com/symfony/expression-language);
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*:doc:`Install it via Composer</components/using_components>` (``symfony/expression-language`` on `Packagist`_).
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* Use the official Git repository (https://github.com/symfony/expression-language);
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How can the Expression Engine Help Me?
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--------------------------------------
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The purpose of the component is to allow users to use expressions inside
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configuration for more complex logic. In the Symfony2 Framework, for example,
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expressions can be used in security, for validation rules, and in route matching.
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Besides using the component in the framework itself, the ExpressionLanguage
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component is a perfect candidate for the foundation of a *business rule engine*.
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The idea is to let the webmaster of a website configure things in a dynamic
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way without using PHP and without introducing security problems:
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..code-block::text
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# Get the special price if
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user.getGroup() in ['good_customers', 'collaborator']
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# Promote article to the homepage when
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article.commentCount > 100 and article.category not in ["misc"]
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# Send an alert when
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product.stock < 15
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Expressions can be seen as a very restricted PHP sandbox and are immune to
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external injections as you must explicitly declare which variables are available
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in an expression.
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Usage
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-----
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The ExpressionLanguage component can compile and evaluate expressions.
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Expressions are one-linerswhich most of the timereturn aboolean, you can
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compare them tothe expression in an ``if``statement. A simple example of an
29-
expression is ``1 + 2``. You can also use more complicated expressions, such
30-
as ``someArray[3].someMethod('bar')``.
54+
Expressions are one-linersthat oftenreturn aBoolean, which can be used
55+
by the code executingthe expression in an ``if``statements. A simple example
56+
of anexpression is ``1 + 2``. You can also use more complicated expressions,
57+
suchas ``someArray[3].someMethod('bar')``.
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The component provides 2 ways to work with expressions:
3360

@@ -49,7 +76,35 @@ The main class of the component is
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Expression Syntax
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-----------------
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52-
See":doc:`/components/expression_language/syntax`" to learn the syntax of the
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See:doc:`/components/expression_language/syntax` to learn the syntax of the
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ExpressionLanguage component.
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Passing in Variables
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--------------------
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You can also pass variables into the expression, which can be of any valid
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PHP type (including objects)::
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use Symfony\Component\ExpressionLanguage\ExpressionLanguage;
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$language = new ExpressionLanguage();
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class Apple
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{
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public $variety;
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}
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$apple = new Apple();
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$apple->variety = 'Honeycrisp';
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echo $language->evaluate(
101+
'fruit.variety',
102+
array(
103+
'fruit' => $apple,
104+
)
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);
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This will print "Honeycrisp". For more information, see the:doc:`/components/expression_language/syntax`
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entry, especially:ref:`component-expression-objects` and:ref:`component-expression-arrays`.
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55110
.. _Packagist:https://packagist.org/packages/symfony/expression-language

‎components/expression_language/syntax.rst

Lines changed: 168 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -9,24 +9,102 @@ expression syntax of Twig. In this document, you can find all supported
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syntaxes.
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Supported Literals
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~~~~~~~~~~~~~~~~~~
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------------------
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The component supports:
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* **strings** - single and double quotes (e.g. ``'hello'``)
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* **numbers** - e.g. ``103``
18-
* **arrays** - usingtwig notation (e.g. ``[1, 2]``)
19-
* **hashes** - usingtwig notation (e.g. ``{ foo: 'bar' }``)
18+
* **arrays** - usingJSON-like notation (e.g. ``[1, 2]``)
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* **hashes** - usingJSON-like notation (e.g. ``{ foo: 'bar' }``)
2020
* **booleans** - ``true`` and ``false``
2121
* **null** - ``null``
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.. _component-expression-objects:
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Working with Objects
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--------------------
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When passing objects into an expression, you can use different syntaxes to
29+
access properties and call methods on the object.
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Accessing Public Methods
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~~~~~~~~~~~~~~~~~~~~~~~~
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Public properties on objects can be accessed by using the ``.`` syntax, similar
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to #"diff-7c1d01740af652e83a4feff0be6d870005f9641c2eb108854514f456c2e9d0ca-22-36-0" data-selected="false" role="gridcell" tabindex="-1" valign="top">
36+
37+
class Apple
38+
{
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public $variety;
40+
}
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42+
$apple = new Apple();
43+
$apple->variety = 'Honeycrisp';
44+
45+
echo $language->evaluate(
46+
'fruit.variety',
47+
array(
48+
'fruit' => $apple,
49+
)
50+
);
51+
52+
Calling Methods
53+
~~~~~~~~~~~~~~~
54+
55+
The ``.`` syntax can also be used to call methods on an object, similar to
56+
#"diff-7c1d01740af652e83a4feff0be6d870005f9641c2eb108854514f456c2e9d0ca-22-57-0" data-selected="false" role="gridcell" tabindex="-1" valign="top">
57+
58+
class Robot
59+
{
60+
public function sayHi($times)
61+
{
62+
$greetings = array();
63+
for ($i = 0; $i < $times; $i++) {
64+
$greetings[] = 'Hi';
65+
}
66+
67+
return implode(' ', $greetings).'!';
68+
}
69+
}
70+
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$robot = new Robot();
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73+
echo $language->evaluate(
74+
'robot.sayHi(3)',
75+
array(
76+
'robot' => $robot,
77+
)
78+
);
79+
80+
This will print "Hi Hi Hi!";
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82+
.. _component-expression-arrays:
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84+
Working with Arrays
85+
-------------------
86+
87+
If you pass an array into an expression, use the ``[]`` syntax to access
88+
array keys, similar to #"diff-7c1d01740af652e83a4feff0be6d870005f9641c2eb108854514f456c2e9d0ca-22-89-0" data-selected="false" role="gridcell" tabindex="-1" valign="top">
89+
90+
$data = array('life' => 10, 'universe' => 10, 'everything' => 22);
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echo $language->evaluate(
93+
'data["life"] + data["universe"] + data["everything"]',
94+
array(
95+
'data' => $data,
96+
)
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);
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99+
This will print ``42``.
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23101
Supported Operators
24-
~~~~~~~~~~~~~~~~~~~
102+
-------------------
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26104
The component comes with a lot of operators:
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28106
Arithmetic Operators
29-
....................
107+
~~~~~~~~~~~~~~~~~~~~
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31109
* ``+`` (addition)
32110
* ``-`` (subtraction)
@@ -35,20 +113,33 @@ Arithmetic Operators
35113
* ``%`` (modulus)
36114
* ``**`` (pow)
37115

116+
For example::
117+
118+
echo $language->evaluate(
119+
'life + universe + everything',
120+
array(
121+
'life' => 10,
122+
'universe' => 10,
123+
'everything' => 22,
124+
)
125+
);
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This will print out ``42``.
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38129
Assignment Operators
39-
....................
130+
~~~~~~~~~~~~~~~~~~~~
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41132
* ``=``
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43134
Bitwise Operators
44-
.................
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~~~~~~~~~~~~~~~~~
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46137
* ``&`` (and)
47138
* ``|`` (or)
48139
* ``^`` (xor)
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50141
Comparison Operators
51-
....................
142+
~~~~~~~~~~~~~~~~~~~~
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53144
* ``==`` (equal)
54145
* ``===`` (identical)
@@ -67,31 +158,95 @@ Comparison Operators
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68159
$language->evaluate('not "foo" matches "/bar/"'); // returns true
69160

161+
Examples::
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$ret1 = $language->evaluate(
164+
'life == everything',
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array(
166+
'life' => 10,
167+
'universe' => 10,
168+
'everything' => 22,
169+
)
170+
);
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$ret2 = $language->evaluate(
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'life > everything',
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array(
175+
'life' => 10,
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'universe' => 10,
177+
'everything' => 22,
178+
)
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);
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These would both return ``false``.
182+
70183
Logical Operators
71-
.................
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~~~~~~~~~~~~~~~~~
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73186
* ``not`` or ``!``
74187
* ``and`` or ``&&``
75188
* ``or`` or ``||``
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190+
For example::
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$ret = $language->evaluate(
193+
'life < universe or life < everything',
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array(
195+
'life' => 10,
196+
'universe' => 10,
197+
'everything' => 22,
198+
)
199+
);
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201+
This would return ``true``.
202+
77203
String Operators
78-
................
204+
~~~~~~~~~~~~~~~~
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80206
* ``~`` (concatenation)
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208+
For example::
209+
210+
$ret4 = $language->evaluate(
211+
'firstName~" "~lastName',
212+
array(
213+
'firstName' => 'Arthur',
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'lastName' => 'Dent',
215+
)
216+
);
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This would print out ``Arthur Dent``.
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82220
Array Operators
83-
...............
221+
~~~~~~~~~~~~~~~
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85223
* ``in`` (contain)
86224
* ``not in`` (does not contain)
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226+
For example::
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228+
class User
229+
{
230+
public $group;
231+
}
232+
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$user = new User();
234+
$user->group = 'human_resources';
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$ret5 = $language->evaluate(
237+
'user.group in ["human_resources", "marketing"]',
238+
array(
239+
'user' => $user
240+
)
241+
);
242+
88243
Numeric Operators
89-
.................
244+
~~~~~~~~~~~~~~~~~
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91246
* ``..`` (range)
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93248
Ternary Operators
94-
.................
249+
~~~~~~~~~~~~~~~~~
95250

96251
* ``foo ? 'yes' : 'no'``
97252
* ``foo ?: 'no'`` (equal to ``foo ? foo : 'no'``)

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