模型元数据(Models Meta-Data) ============================== To speed up development :doc:`Phalcon\\Mvc\\Model <../api/Phalcon_Mvc_Model>` helps you to query fields and constraints from tables related to models. To achieve this, :doc:`Phalcon\\Mvc\\Model\\MetaData <../api/Phalcon_Mvc_Model_MetaData>` is available to manage and cache table meta-data. Sometimes it is necessary to get those attributes when working with models. You can get a meta-data instance as follows: .. code-block:: php getModelsMetaData(); // Get robots fields names $attributes = $metaData->getAttributes($robot); print_r($attributes); // Get robots fields data types $dataTypes = $metaData->getDataTypes($robot); print_r($dataTypes); 缓存元数据(Caching Meta-Data) ------------------------------- Once the application is in a production stage, it is not necessary to query the meta-data of the table from the database system each time you use the table. This could be done caching the meta-data using any of the following adapters: +---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+ | Adapter | Description | API | +=========+===============================================================================================================================================================================================================================================================================================================================================+===========================================================================================+ | Memory | This adapter is the default. The meta-data is cached only during the request. When the request is completed, the meta-data are released as part of the normal memory of the request. This adapter is perfect when the application is in development so as to refresh the meta-data in each request containing the new and/or modified fields. | :doc:`Phalcon\\Mvc\\Model\\MetaData\\Memory <../api/Phalcon_Mvc_Model_MetaData_Memory>` | +---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+ | Session | This adapter stores meta-data in the :code:`$_SESSION` superglobal. This adapter is recommended only when the application is actually using a small number of models. The meta-data are refreshed every time a new session starts. This also requires the use of :code:`session_start()` to start the session before using any models. | :doc:`Phalcon\\Mvc\\Model\\MetaData\\Session <../api/Phalcon_Mvc_Model_MetaData_Session>` | +---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+ | Apc | This adapter uses the `Alternative PHP Cache (APC)`_ to store the table meta-data. You can specify the lifetime of the meta-data with options. This is the most recommended way to store meta-data when the application is in production stage. | :doc:`Phalcon\\Mvc\\Model\\MetaData\\Apc <../api/Phalcon_Mvc_Model_MetaData_Apc>` | +---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+ | XCache | This adapter uses `XCache`_ to store the table meta-data. You can specify the lifetime of the meta-data with options. This is the most recommended way to store meta-data when the application is in production stage. | :doc:`Phalcon\\Mvc\\Model\\MetaData\\Xcache <../api/Phalcon_Mvc_Model_MetaData_Xcache>` | +---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+ | Files | This adapter uses plain files to store meta-data. By using this adapter the disk-reading is increased but the database access is reduced. | :doc:`Phalcon\\Mvc\\Model\\MetaData\\Files <../api/Phalcon_Mvc_Model_MetaData_Files>` | +---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+ As other ORM's dependencies, the metadata manager is requested from the services container: .. code-block:: php 86400, "prefix" => "my-prefix" ) ); return $metaData; }; 元数据策略(Meta-Data Strategies) ---------------------------------- As mentioned above the default strategy to obtain the model's meta-data is database introspection. In this strategy, the information schema is used to know the fields in a table, its primary key, nullable fields, data types, etc. You can change the default meta-data introspection in the following way: .. code-block:: php 86400, "prefix" => "my-prefix" ) ); // Set a custom meta-data introspection strategy $metaData->setStrategy(new MyIntrospectionStrategy()); return $metaData; }; 数据库内部策略(Database Introspection Strategy) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This strategy doesn't require any customization and is implicitly used by all the meta-data adapters. 注释策略(Annotations Strategy) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This strategy makes use of :doc:`annotations ` to describe the columns in a model: .. code-block:: php 86400, "prefix" => "my-prefix" ) ); // Set a custom meta-data database introspection $metaData->setStrategy(new StrategyAnnotations()); return $metaData; }; 自定义元数据(Manual Meta-Data) -------------------------------- Phalcon can obtain the metadata for each model automatically without the developer must set them manually using any of the introspection strategies presented above. The developer also has the option of define the metadata manually. This strategy overrides any strategy set in the meta-data manager. New columns added/modified/removed to/from the mapped table must be added/modified/removed also for everything to work properly. The following example shows how to define the meta-data manually: .. code-block:: php array( 'id', 'name', 'type', 'year' ), // Every column part of the primary key MetaData::MODELS_PRIMARY_KEY => array( 'id' ), // Every column that isn't part of the primary key MetaData::MODELS_NON_PRIMARY_KEY => array( 'name', 'type', 'year' ), // Every column that doesn't allows null values MetaData::MODELS_NOT_NULL => array( 'id', 'name', 'type' ), // Every column and their data types MetaData::MODELS_DATA_TYPES => array( 'id' => Column::TYPE_INTEGER, 'name' => Column::TYPE_VARCHAR, 'type' => Column::TYPE_VARCHAR, 'year' => Column::TYPE_INTEGER ), // The columns that have numeric data types MetaData::MODELS_DATA_TYPES_NUMERIC => array( 'id' => true, 'year' => true ), // The identity column, use boolean false if the model doesn't have // an identity column MetaData::MODELS_IDENTITY_COLUMN => 'id', // How every column must be bound/casted MetaData::MODELS_DATA_TYPES_BIND => array( 'id' => Column::BIND_PARAM_INT, 'name' => Column::BIND_PARAM_STR, 'type' => Column::BIND_PARAM_STR, 'year' => Column::BIND_PARAM_INT ), // Fields that must be ignored from INSERT SQL statements MetaData::MODELS_AUTOMATIC_DEFAULT_INSERT => array( 'year' => true ), // Fields that must be ignored from UPDATE SQL statements MetaData::MODELS_AUTOMATIC_DEFAULT_UPDATE => array( 'year' => true ), // Default values for columns MetaData::MODELS_DEFAULT_VALUES => array( 'year' => '2015' ), // Fields that allow empty strings MetaData::MODELS_EMPTY_STRING_VALUES => array( 'name' => true ) ); } } .. _Alternative PHP Cache (APC): http://www.php.net/manual/zh/book.apc.php .. _XCache: http://xcache.lighttpd.net/