Using Collections in Magento

Last modified by houtsnip on Tue, March 20, 2012 06:55
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A collection is a Model type containing other Models, it is basically used in Magento to handle product lists (ie. from a category or a bundle option), but not only.

TO DO: Explain how Magento Implements a collection - Use this to explain how Magento implements a collection by looking at code in a model, so that people can learn to write their own collections

This is a simple example of loading some product collection from a category and ordering them on their product name using Magento’s API.

  1. $collection = Mage::getModel('catalog/category')->load($categoryId)
  2.     ->getProductCollection()
  3.     ->addAttributeToSort('name', 'ASC');

To sort using multiple Fields, you can chain calls to the Collection’s method addAttributeToSort(preferred)

  1. $collection = Mage::getModel('module/model_name')->getCollection()
  2.     ->addAttributeToSort('order', 'ASC')
  3.     ->addAttributeToSort('last_name', 'ASC')
  4.     ->addAttributeToSort('first_name', 'ASC')
  5. ;

TODO: use Magento’s API use cases, not Zend_Db_Select ones.

You can also pass IF/THEN statements, but be sure to use the proper quotation of your table’s fields.

  1. $collection = Mage::getModel('module/model_name')->getCollection();
  2. $collection->getSelect()->order( array('IF(`order`>0, `order`, 9999) ASC',
  3.      'last_name ASC', 'first_name ASC') );

In this example, the table will be sorted by the order field, then by last name, then by first name, where order is greater than zero, followed by order being equal to or less than zero, all ascending.

Joining Tables

To add SQL joins to a select

  1. $collection = Mage::getModel('module/model_name')->getCollection();
  2. $collection->getSelect()->join( array('table_alias'=>$this->getTable('module/table_name')), 'main_table.foreign_id = table_alias.primary_key', array('table_alias.*'), 'schema_name_if_different');

In this example the join method takes an array of alias⇒table_name key pairs, then a standard join clause using `main_table` to refer to the original select, then an array of fields to be retrieved in the join (defaults to *), a different schema can be specified as a last parameter.

→join defaults to an inner join, others can be used:

→joinInner() →joinLeft() →joinRight() →joinFull() →joinCross() →joinNatural()

See lib/Zend/Db/Select.php for source.

Collection Manipulation Methods

Varien_Data_Collection

Varien/Data/Collection.php

addFilter($field, $value, $type = ‘and’)
addItem(Varien_Object $item)
clear()
count()
distinct($flag)
each($obj_method, $args=array())
getAllIds()
getCacheKey()
getCacheLifetime()
getCacheTags()
getColumnValues($colName)
getCurPage($displacement = 0)
getFirstItem()
getFlag($flag)
getItemByColumnValue($column, $value)
getItemById($idValue)
getItems()
getItemsByColumnValue($column, $value)
getIterator()
getLastItem()
getLastPageNumber()
getNewEmptyItem()
getPageSize()
getSize()
hasFlag($flag)
isLoaded()
loadData($printQuery = false, $logQuery = false)
load($printQuery = false, $logQuery = false)
removeItemByKey($key)
setCacheKey($key)
setCacheTags($tags)
setCurPage($page)
setDataToAll($key, $value=null)
setFlag($flag, $value = null)
setOrder($field, $direction = self::SORT_ORDER_DESC)
setPageSize($size)
toArray($arrRequiredFields = array())
toOptionArray()
toOptionHash()
toXml()
walk($callback, array $args=array())

Varien_Data_Collection_Db

Varien/Data/Collection/Db.php

Inherits above methods for Varien_Data_Collection, and in addition (re)defines the following:

addBindParam($name, $value)
addFieldToFilter($field, $condition=null)
addOrder($field, $direction = self::SORT_ORDER_DESC)
distinct($flag)
getConnection()
getData()
getIdFieldName()
getSelect()
getSelectCountSql()
getSize()
initCache($object, $idPrefix, $tags)
loadData($printQuery = false, $logQuery = false)
load($printQuery = false, $logQuery = false)
printLogQuery($printQuery = false, $logQuery = false, $sql = null)
resetData()
setConnection($conn)
setOrder($field, $direction = self::SORT_ORDER_DESC)
unshiftOrder($field, $direction = self::SORT_ORDER_DESC)

Filter Condition Codes

Attribute Code SQL Equivalent Description
eq =
neq !=
like LIKE
nlike NOT LIKE
in IN ()
nin NOT IN ()
is IS
notnull IS NOT NULL
null IS NULL
moreq >=
gt >
lt <
gteq >=
lteq <=
finset FIND_IN_SET()
from >= for use with dates
to <= for use with dates
date optional flag for use with from/to to specify that comparison value should first be converted to a date
datetime optional flag for use with from/to to specify that comparison value should first be converted to a datetime

If an array is passed but no attribute code specified, it will be interpreted as a group of OR conditions that will be processed in the same way.

If no attribute code is specified, it defaults to eq.

E.g.

  1. $collection->addAttributeToFilter('field_name', array(
  2.     'in' => array(1, 2, 3),
  3.     ));
  4.  
  5. $collection->addAttributeToFilter('date_field', array(
  6.    'from' => '2000-09-10',
  7.     ));
  8.  
  9. $collection->addAttributeToFilter('date_field', array(
  10.     'from' => '10 September 2000',
  11.     'from' => '11 September 2000',
  12.     'date' => true, // specifies conversion of comparison values
  13.     ));
  14.  
  15. $collection->addAttributeToFilter('field_name', 1); // tests for equality
  16.  
  17. // Add OR condition:
  18. $collection->addAttributeToFilter(array(
  19.     array(
  20.         'attribute' => 'field_name',
  21.         'in'        => array(1, 2, 3),
  22.         ),
  23.     array(
  24.         'attribute' => 'date_field',
  25.         'from'      => '2000-09-10',
  26.         ),
  27.     ));

Mage_Eav_Model_Entity_Collection

Mage/Eav/Model/Entity/Collection/Abstract.php

Inherits above methods for Varien_Data_Collection_Db, and in addition (re)defines the following:

addAttributeToFilter($attribute, $condition=null, $joinType=’inner’) adds WHERE clause on $attribute specified by $condition
addAttributeToSelect($attribute, $joinType=false) gets the value for $attribute in the SELECT clause;
specify * to get all attributes (i.e. to execute SELECT *)
addAttributeToSort($attribute, $dir=’asc’) adds ORDER BY clause on $attribute
addEntityTypeToSelect($entityType, $prefix) doesn’t seem to do anything - don’t use
addExpressionAttributeToSelect($alias, $expression, string|array $attribute) adds SQL expression $expression, using $alias, to SELECT clause (typically containing aggregate functions such as SUM(), COUNT());
when $attribute specifies a single attribute as a string, $expression can reference the attribute as simply {{attribute}}, but when passing an array of attributes, each attribute must be referenced in $expression by the name of the specific attribute;
N.B. use with groupByAttribute() when including aggregate functions q.v.
addFieldToFilter($attribute, $condition=null) alias for addAttributeToFilter()
addItem(Varien_Object $object) adds an object to the collection
addStaticField($field) specifies $field as being static, i.e. as existing on the entity table itself, rather than in the EAV table
delete() deletes all entities in the collection
exportToArray() returns collection data as a 2D array
getAllIds($limit=null, $offset=null) returns array of all entity IDs selected by current WHERE clause (optionally specifying $limit and $offset)
getAllIdsSql() not recommended - don’t use
getAttribute($attributeCode) for specified $attributeCode, returns Mage_Eav_Model_Entity_Attribute_Abstract object of the entity object used by the collection (i.e. calls getAttribute($attributeCode) on the entity object and returns the result)
getEntity() returns Mage_Eav_Model_Entity_Abstract object used by collection for attributes
getLoadedIds() returns array of IDs of currently loaded entities
getResource() returns Mage_Core_Model_Resource_Abstract instance;
actually an alias for getEntity() q.v. (an entity is a special type of resource, that is, Mage_Eav_Model_Entity_Abstract extends Mage_Core_Model_Resource_Abstract)
getRowIdFieldName() returns field name of ID attribute for entities in the collection
getTable($table) alias for Mage::getSingleton(‘core/resource’)->getTableName($table)
groupByAttribute($attribute) adds $attribute to GROUP BY clause
importFromArray($arr) imports 2D array into collection as objects
joinAttribute($alias, Mage_Eav_Model_Entity_Attribute_Abstract|string $attribute, string $bind, string $filter=null, string $joinType=’inner’, $storeId=null) joins another entity and adds attribute from joined entity, using $alias, to SELECT clause;
$attribute can specify attribute object, or string in format [entity]/[attribute];
$bind specifies attribute of the main entity on which to make join;
$filter specifies primary key of the joined entity on which to make join (normally defaults to entity_id);
$joinType should be inner or left
joinField($alias, $table, $field, $bind, $cond=null, $joinType=’inner’) joins regular table field using an attribute as foreign key
joinTable($table, $bind, $fields=null, $cond=null, $joinType=’inner’) joins table $table
load($printQuery = false, $logQuery = false) runs query and load data into collection;
specify $printQuery as true to print SQL for debugging
removeAttributeToSelect($attribute=null) removes $attribute from SELECT clause;
specify null to remove all attributes
save() saves all entities in the collection
setEntity(string|object $entity) sets entity object (i.e. Mage_Eav_Model_Entity_Abstract) used by collection for attributes
setObject(Varien_Object $object=null) sets template object for the collection
setOrder(string| $attribute, $dir=’desc’) alias for addAttributeToSort() q.v., identical except that it can accept array of attributes, and default $dir is desc;
N.B. overrides parent function
setPage($pageNum, $pageSize) sets LIMIT clause by specifying page number (one-indexed) and number of records per page;
N.B. equivalent to calling setCurPage($pageNum) and setPageSize($pageSize) q.q.v.
setRowIdFieldName($fieldName) returns field name of ID attribute for entities in the collection
toArray(array $arrAttributes=array()) calls toArray($attAttributes) on each entity in collection, and returns result as array



 

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