Entity Querying

The real power behind Nymph is the entity querying system. After all, what's the use of having complex data and relationships if you can't find them?

Factory Method

The simplest way to get an entity is usually its factory static method. The Entity class's factory method expects a GUID as an argument. However, the author of an entity's class can use whatever they like as arguments. For example, the User class in 2be takes either a GUID or a username. The method will return a brand new entity if the queried entity is not found.

ℹ️ Tip: If you're using a user provided value as the GUID, casting it to an int will ensure it is evaluated as a GUID. Also, non-numeric values will be evaluated as 0, resulting in a new entity, since no entity has GUID 0. Then you can determine if it was found by checking that guid is set.

Getting Entities Using the Factory Method in PHP

```php // Most entities use a GUID. $baz = FoobarBaz::factory((int) $_REQUEST['id']);

if (!isset($baz->guid)) { echo 'The specified Foobar Baz cannot be found!'; return; }

// When selecting a user (which is a class that extends Entity) in 2be, you can use a GUID or a username. $cronUser = User::factory('cron'); if (!isset($cronUser->guid)) { echo 'Can't find the cron user! Have you created one yet?'; return; }

// If the script made it to this point, both $baz and $cronUser were found! echo 'Hooray! I found the Foobar Baz you wanted and the cron user!';

## Nymph's Query Language

The really powerful way of querying entities is Nymph's `getEntities` and `getEntity` methods.

The first argument to these methods is an options array. It is an associative array in PHP or an object in JS. The options array can be empty, in which case the `Entity` class will be used for returned entities. The following is a list of options which Nymph supports.

<div dir="rtl">Entity Querying Options</div>
Option | Type | Default | Description
------ | ---- | ------- | -----------
class | string | "Entity" | The class used to create each entity. It must have a factory static method that returns a new instance.
limit | int | null | The limit of entities to be returned. Not needed when using getEntity, as it always returns only one.
offset | int | 0 | The offset from the oldest (or newest if reversed) matching entity to start retrieving.
reverse | bool | false | If true, entities will be retrieved from newest to oldest. Therefore, offset will be from the newest entity.
sort | string | "cdate" | How to sort the entities. Accepts "guid", "cdate", and "mdate".

A plugin or Nymph driver is free to add extra options, but you should consider prepending its name to the name of the option. For example, if your plugin, EntityVersions, wants to add the option "date", it should use "EntityVersionsDate".

Every argument following the options array is a selector. A selector is an associative array (object in JS) of criteria. An entity must match each selector's criteria to be returned. The first member of the array (the value at index 0, or the "type" entry in JS) is the type of selector, which determines how the criteria are matched against an entity's data.

<div dir="rtl">Entity Selector Types</div>
Type | Name | Description
---- | ---- | -----------
& | And | All values in the selector must be true.
\| | Or | At least one value in the selector must be true.
!& | Not And | All values in the selector must be false.
!\| | Not Or | At least one value in the selector must be false.

The subsequent members of the array are the criteria of the selector. They must be in the form `$selector['name'] = $value`, or `$selector['name'] = array($value1, $value2,...)`. They can be negated by prepending a bang (!) to the name, such as `$selector['!tag'] = 'user'`.

<div dir="rtl">Entity Selector Criteria</div>
Name | Value | Condition | Example Selector | Matching Entity
---- | ----- | --------- | ---------------- | ---------------
guid | A GUID. | True if the entity's GUID is equal. | array('&', 'guid' => 12) | $entity->guid = 12;
tag | A tag. | True if the entity has the tag. | array('&', 'tag' => 'foobar') | $entity->addTag('foobar');
isset | A name. | True if the named variable exists and is not null. | array('&', 'isset' => 'foo') | $entity->foo = 0;
data | An array with a name, then value. | True if the named variable is defined and equal. | array('&', 'data' => array('foo', false)) | $entity->foo = 0;
strict | An array with a name, then value. | True if the named variable is defined and identical. | array('&', 'strict' => array('foo', 0)) | $entity->foo = 0;
array | An array with a name, then value. | True if the named variable is an array containing the value. Uses `inArray`. | array('&', 'array' => array('foo', 'bar')) | $entity->foo = array('bar', 'baz');
match | An array with a name, then regular expression. | True if the named variable matches. Uses `preg_match`. More powerful than "pmatch" but slower. Must be surrounded by "/" delimiters. | array('&', 'match' => array('foo', '/(ba(r\|z))+/')) | $entity->foo = 'foobarbaz';
pmatch | An array with a name, then regular expression. | True if the named variable matches. Uses POSIX RegExp. Case sensitive. Faster than "match". Must *not* be surrounded by any delimiters. | array('&', 'match' => array('foo', 'bar.*z')) | $entity->foo = 'foobarbaz';
like | An array with a name, then pattern. | True if the named variable matches. Uses % for variable length wildcard and _ for single character wildcard. | array('&', 'match' => array('foo', 'f%bar_az')) | $entity->foo = 'foobarbaz';
gt | An array with a name, then value. | True if the named variable is greater than the value. | array('&', 'gt' => array('foo', 5)) | $entity->foo = 6;
gte | An array with a name, then value. | True if the named variable is greater than or equal to the value. | array('&', 'gte' => array('foo', 6)) | $entity->foo = 6;
lt | An array with a name, then value. | True if the named variable is less than the value. | array('&', 'lt' => array('foo', 7)) | $entity->foo = 6;
lte | An array with a name, then value. | True if the named variable is less than or equal to the value. | array('&', 'lte' => array('foo', 6)) | $entity->foo = 6;
ref | An array with a name, then either a entity, or a GUID. | True if the named variable is the entity or an array containing the entity. | array('&', 'ref' => array('foo', 12)) | $entity->foo = Entity::factory(12);

## Querying Examples

So putting it all together, you can specify any of the options, and any number of selectors to find the exact entities you want.

<div dir="rtl">Getting Entities by Querying</div>
```js
// Get all entities using the Entity class. (The class determines the
// database table.)
var entitiesPromise = Nymph.getEntities();

// Get only the first entity using the Entity class.
var entityPromise = Nymph.getEntity();

// Get the latest FoobarBaz entity.
var entityPromise = Nymph.getEntity({'class': 'FoobarBaz', 'reverse': true});

// Get all baz tagged entities, using the FoobarBaz class.
var entitiesPromise = Nymph.getEntities(
    {'class': 'FoobarBaz'},
    {'type': '&',
      'tag': 'baz'
    }
  );

// Get the five newest bar and baz tagged entities.
var entitiesPromise = Nymph.getEntities(
    {'class': 'FoobarBaz', 'reverse': true, 'limit': 5},
    {'type': '&',
      'tag': ['bar', 'baz']
    }
  );

// Get baz tagged entities with names.
var entitiesPromise = Nymph.getEntities(
    {'class': 'FoobarBaz'},
    {'type': '&',
      'tag': 'baz',
      'isset': 'name'
    }
  );

// Get baz tagged entities without names.
var entitiesPromise = Nymph.getEntities(
    {'class': 'FoobarBaz'},
    {'type': '&',
      'tag': 'baz',
      '!isset': 'name'
    }
  );

// Get baz tagged entities with either first names or last names.
var entitiesPromise = Nymph.getEntities(
    {'class': 'FoobarBaz'},
    {'type': '&',
      'tag': 'baz'
    },
    {'type': '|',
      'isset': ['first_name', 'last_name']
    }
  );

// Get baz tagged entities created since yesterday.
var entitiesPromise = Nymph.getEntities(
    {'class': 'FoobarBaz'},
    {'type': '&',
      'tag': 'baz',
      'gt': ['cdate', Math.round((new Date()).getTime() / 1000) - 86400]
    }
  );

// Get baz tagged entities with names, who either make not greater than
// 8 dollars pay or are under 22.
var entitiesPromise = Nymph.getEntities(
    {'class': 'FoobarBaz'},
    {'type': '&',
      'tag': 'baz',
      'isset': 'name'
    },
    {'type': '!|', // at least one must be false
      'gte': ['age', 22],
      'gt': ['pay', 8]
    }
  );

// Get baz tagged entities named Clark, James, Chris, Christopher,
// Jake, or Jacob.
var entitiesPromise = Nymph.getEntities(
    {'class': 'FoobarBaz'},
    {'type': '&',
      'tag': 'baz'
    },
    {'type': '|',
      'strict': [
        ['name', 'Clark'],
        ['name', 'James']
      ],
      'pmatch': [
        ['name', 'Chris(topher)?'],
        ['name', 'Ja(ke|cob)']
      ]
    }
  );

$nymph = RPHP::_('Nymph');

// Get all entities using the Entity class. (The class determines
// the database table.)
$entities = $nymph->getEntities();

// Get only the first entity using the Entity class.
$entity = $nymph->getEntity();

// Get the latest FoobarBaz entity.
$entity = $nymph->getEntity(array('class' => FoobarBaz, 'reverse' => true));

// Get all baz tagged entities, using the FoobarBaz class.
$entities = $nymph->getEntities(
    array('class' => FoobarBaz),
    array('&',
      'tag' => 'baz'
    )
  );

// Get the five newest bar and baz tagged entities.
$entities = $nymph->getEntities(
    array('class' => FoobarBaz, 'reverse' => true, 'limit' => 5),
    array('&',
      'tag' => array('bar', 'baz')
    )
  );

// Get baz tagged entities with names.
$entities = $nymph->getEntities(
    array('class' => FoobarBaz),
    array('&',
      'tag' => 'baz',
      'isset' => 'name'
    )
  );

// Get baz tagged entities without names.
$entities = $nymph->getEntities(
    array('class' => FoobarBaz),
    array('&',
      'tag' => 'baz',
      '!isset' => 'name'
    )
  );

// Get baz tagged entities with either first names or last names.
$entities = $nymph->getEntities(
    array('class' => FoobarBaz),
    array('&',
      'tag' => 'baz'
    ),
    array('|',
      'isset' => array('first_name', 'last_name')
    )
  );

// Get baz tagged entities created since yesterday.
$entities = $nymph->getEntities(
    array('class' => FoobarBaz),
    array('&',
      'tag' => 'baz',
      'gt' => array('cdate', strtotime('-1 day'))
    )
  );

// Get baz tagged entities with names, who either make not greater
// than 8 dollars pay or are under 22.
$entities = $nymph->getEntities(
    array('class' => FoobarBaz),
    array('&',
      'tag' => 'baz',
      'isset' => 'name'
    ),
    array('!|', // at least one must be false
      'gte' => array('age', 22),
      'gt' => array('pay', 8)
    )
  );

// Get baz tagged entities named Clark, James, Chris, Christopher,
// Jake, or Jacob.
$entities = $nymph->getEntities(
    array('class' => FoobarBaz),
    array('&',
      'tag' => 'baz'
    ),
    array('|',
      'strict' => array(
        array('name', 'Clark'),
        array('name', 'James')
      ),
      'pmatch' => array(
        array('name', 'Chris(topher)?'),
        array('name', 'Ja(ke|cob)')
      )
    )
  );