Data::ObjectDriver::BaUserjContributed Perl DData::ObjectDriver::BaseObject(3)NAMEData::ObjectDriver::BaseObject - base class for modeled objects
SYNOPSIS
package Ingredient;
use base qw( Data::ObjectDriver::BaseObject );
__PACKAGE__->install_properties({
columns => [ 'ingredient_id', 'recipe_id', 'name', 'quantity' ],
datasource => 'ingredient',
primary_key => [ 'recipe_id', 'ingredient_id' ],
driver => FoodDriver->driver,
});
__PACKAGE__->has_a(
{ class => 'Recipe', column => 'recipe_id', }
);
package main;
my ($ingredient) = Ingredient->search({ recipe_id => 4, name => 'rutabaga' });
$ingredient->quantity(7);
$ingredient->save();
DESCRIPTIONData::ObjectDriver::BaseObject provides services to data objects
modeled with the Data::ObjectDriver object relational mapper.
CLASS DEFINITION
"Class->install_properties(\%params)"
Defines all the properties of the specified object class. Generally you
should call "install_properties()" in the body of your class
definition, so the properties can be set when the class is "use"d or
"require"d.
Required members of %params are:
· "columns"
All the columns in the object class. This property is an arrayref.
· "datasource"
The identifier of the table in which the object class's data are
stored. Usually the datasource is simply the table name, but the
datasource can be decorated into the table name by the
"Data::ObjectDriver::DBD" module if the database requires special
formatting of table names.
· "driver" or "get_driver"
The driver used to perform database operations (lookup, update,
etc) for the object class.
"driver" is the instance of "Data::ObjectDriver" to use. If your
driver requires configuration options not available when the
properties are initially set, specify a coderef as "get_driver"
instead. It will be called the first time the driver is needed,
storing the driver in the class's "driver" property for subsequent
calls.
The optional members of %params are:
· "primary_key"
The column or columns used to uniquely identify an instance of the
object class. If one column (such as a simple numeric ID)
identifies the class, "primary_key" should be a scalar. Otherwise,
"primary_key" is an arrayref.
· "column_defs"
Specifies types for specially typed columns, if any, as a hashref.
For example, if a column holds a timestamp, name it in
"column_defs" as a "date" for proper handling with some
"Data::ObjectDriver::Driver::DBD" database drivers. Columns for
which types aren't specified are handled as "char" columns.
Known "column_defs" types are:
· "blob"
A blob of binary data. "Data::ObjectDriver::Driver::DBD::Pg"
maps this to "DBI::Pg::PG_BYTEA", "DBD::SQLite" to
"DBI::SQL_BLOB" and "DBD::Oracle" to "ORA_BLOB".
· "bin_char"
A non-blob string of binary data.
"Data::ObjectDriver::Driver::DBD::SQLite" maps this to
"DBI::SQL_BINARY".
Other types may be defined by custom database drivers as needed, so
consult their documentation.
· "db"
The name of the database. When used with
"Data::ObjectDriver::Driver::DBI" type object drivers, this name is
passed to the "init_db" method when the actual database handle is
being created.
Custom object drivers may define other properties for your object
classes. Consult the documentation of those object drivers for more
information.
"Class->install_column($col, $def)"
Modify the Class definition to declare a new column $col of definition
<$def> (see column_defs).
"Class->has_a(@definitions)"
NOTE: "has_a" is an experimental system, likely to both be buggy and
change in future versions.
Defines a foreign key reference between two classes, creating accessor
methods to retrieve objects both ways across the reference. For each
defined reference, two methods are created: one for objects of class
"Class" to load the objects they reference, and one for objects of the
referenced class to load the set of "Class" objects that reference
them.
For example, this definition:
package Ingredient;
__PACKAGE__->has_a(
{ class => 'Recipe', column => 'recipe_id' },
);
would create "Ingredient->recipe_obj" and "Recipe->ingredient_objs"
instance methods.
Each member of @definitions is a hashref containing the parameters for
creating one accessor method. The required members of these hashes are:
· "class"
The class to associate.
· "column"
The column or columns in this class that identify the primary key
of the associated object. As with primary keys, use a single scalar
string for a single column or an arrayref for a composite key.
The optional members of "has_a()" definitions are:
· "method"
The name of the accessor method to create.
By default, the method name is the concatenated set of column names
with each "_id" suffix removed, and the suffix "_obj" appended at
the end of the method name. For example, if "column" were
"['recipe_id', 'ingredient_id']", the resulting method would be
called "recipe_ingredient_obj" by default.
· "cached"
Whether to keep a reference to the foreign object once it's loaded.
Subsequent calls to the accessor method would return that reference
immediately.
· "parent_method"
The name of the reciprocal method created in the referenced class
named in "class".
By default, that method is named with the lowercased name of the
current class with the suffix "_objs". For example, if in your
"Ingredient" class you defined a relationship with "Recipe" on the
column "recipe_id", this would create a "$recipe->ingredient_objs"
method.
Note that if you reference one class with multiple sets of fields,
you can omit only one parent_method; otherwise the methods would be
named the same thing. For instance, if you had a "Friend" class
with two references to "User" objects in its "user_id" and
"friend_id" columns, one of them would need a "parent_method".
"Class->has_partitions(%param)"
Defines that the given class is partitioned, configuring it for use
with the "Data::ObjectDriver::Driver::SimplePartition" object driver.
Required members of %param are:
· "number"
The number of partitions in which objects of this class may be
stored.
· "get_driver"
A function that returns an object driver, given a partition ID and
any extra parameters specified when the class's
"Data::ObjectDriver::Driver::SimplePartition" was instantiated.
Note that only the parent object for use with the "SimplePartition"
driver should use "has_partitions()". See
"Data::ObjectDriver::Driver::SimplePartition" for more about
partitioning.
BASIC USAGE
"Class->lookup($id)"
Returns the instance of "Class" with the given value for its primary
key. If "Class" has a complex primary key (more than one column), $id
should be an arrayref specifying the column values in the same order as
specified in the "primary_key" property.
"Class->search(\%terms, [\%args])"
Returns all instances of "Class" that match the values specified in
"\%terms", keyed on column names. In list context, "search" returns the
objects containing those values. In scalar context, "search" returns an
iterator function containing the same set of objects.
Your search can be customized with parameters specified in "\%args".
Commonly recognized parameters (those implemented by the standard
"Data::ObjectDriver" object drivers) are:
· "sort"
A column by which to order the object results.
· "direction"
If set to "descend", the results (ordered by the "sort" column) are
returned in descending order. Otherwise, results will be in
ascending order.
· "limit"
The number of results to return, at most. You can use this with
"offset" to paginate your "search()" results.
· "offset"
The number of results to skip before the first returned result. Use
this with "limit" to paginate your "search()" results.
· "fetchonly"
A list (arrayref) of columns that should be requested. If
specified, only the specified columns of the resulting objects are
guaranteed to be set to the correct values.
Note that any caching object drivers you use may opt to ignore
"fetchonly" instructions, or decline to cache objects queried with
"fetchonly".
· "for_update"
If true, instructs the object driver to indicate the query is a
search, but the application may want to update the data after. That
is, the generated SQL "SELECT" query will include a "FOR UPDATE"
clause.
All options are passed to the object driver, so your driver may support
additional options.
"Class->result(\%terms, [\%args])"
Takes the same %terms and %args arguments that search takes, but
instead of executing the query immediately, returns a
Data::ObjectDriver::ResultSet object representing the set of results.
"$obj->exists()"
Returns true if $obj already exists in the database.
"$obj->save()"
Saves $obj to the database, whether it is already there or not. That
is, "save()" is functionally:
$obj->exists() ? $obj->update() : $obj->insert()
"$obj->update()"
Saves changes to $obj, an object that already exists in its database.
"$obj->insert()"
Adds $obj to the database in which it should exist, according to its
object driver and configuration.
"$obj->remove()"
Deletes $obj from its database.
"$obj->replace()"
Replaces $obj in the database. Does the right thing if the driver knows
how to REPLACE object, ala MySQL.
USAGE
"Class->new(%columns)"
Returns a new object of the given class, initializing its columns with
the values in %columns.
"$obj->init(%columns)"
Initializes $obji by initializing its columns with the values in
%columns.
Override this method if you must do initial configuration to new
instances of $obj's class that are not more appropriate as a
"post_load" callback.
"Class->properties()"
Returns the named object class's properties as a hashref. Note that
some of the standard object class properties, such as "primary_key",
have more convenient accessors than reading the properties directly.
"Class->driver()"
Returns the object driver for this class, invoking the class's
get_driver function (and caching the result for future calls) if
necessary.
"Class->get_driver($get_driver_fn)"
Sets the function used to find the object driver for Class objects
(that is, the "get_driver" property).
Note that once "driver()" has been called, the "get_driver" function is
not used. Usually you would specify your function as the "get_driver"
parameter to "install_properties()".
"Class->is_pkless()"
Returns whether the given object class has a primary key defined.
"Class->is_primary_key($column)"
Returns whether the given column is or is part of the primary key for
"Class" objects.
"$obj->primary_key()"
Returns the values of the primary key fields of $obj.
"Class->primary_key_tuple()"
Returns the names of the primary key fields of "Class" objects.
"$obj->is_same($other_obj)"
Do a primary key check on $obj and $<other_obj> and returns true only
if they are identical.
"$obj->object_is_stored()"
Returns true if the object hasn't been stored in the database yet.
This is particularily useful in triggers where you can then determine
if the object is being INSERTED or just UPDATED.
"$obj->pk_str()"
returns the primay key has a printable string.
"$obj->has_primary_key()"
Returns whether the given object has values for all of its primary key
fields.
"$obj->uncache_object()"
If you use a Cache driver, returned object will be automatically cached
as a result of common retrieve operations. In some rare cases you may
want the cache to be cleared explicitely, and this method provides you
with a way to do it.
"$obj->primary_key_to_terms([$id])"
Returns $obj's primary key as a hashref of values keyed on column
names, suitable for passing as "search()" terms. If $id is specified,
convert that primary key instead of $obj's.
"Class->datasource()"
Returns the datasource for objects of class "Class". That is, returns
the "datasource" property of "Class".
"Class->columns_of_type($type)"
Returns the list of columns in "Class" objects that hold data of type
$type, as an arrayref. Columns are of a certain type when they are set
that way in "Class"'s "column_defs" property.
"$obj->set_values(\%values)"
Sets all the columns of $obj that are members of "\%values" to the
values specified there.
"$obj->set_values_internal(\%values)"
Sets new specified values of $obj, without using any overridden mutator
methods of $obj and without marking the changed columns changed.
"$obj->clone()"
Returns a new object of the same class as $obj containing the same
data, except for primary keys, which are set to "undef".
"$obj->clone_all()"
Returns a new object of the same class as $obj containing the same
data, including all key fields.
"Class->has_column($column)"
Returns whether a column named $column exists in objects of class
<Class>.
"Class->column_names()"
Returns the list of columns in "Class" objects as an arrayref.
"$obj->column_values()"
Returns the columns and values in the given object as a hashref.
"$obj->column($column, [$value])"
Returns the value of $obj's column $column. If $value is specified,
"column()" sets the first.
Note the usual way of accessing and mutating column values is through
the named accessors:
$obj->column('fred', 'barney'); # possible
$obj->fred('barney'); # preferred
"$obj->is_changed([$column])"
Returns whether any values in $obj have changed. If $column is given,
returns specifically whether that column has changed.
"$obj->changed_cols_and_pk()"
Returns the list of all columns that have changed in $obj since it was
last loaded from or saved to the database, as a list.
"$obj->changed_cols()"
Returns the list of changed columns in $obj as a list, except for any
columns in $obj's primary key (even if they have changed).
"Class->lookup_multi(\@ids)"
Returns a list (arrayref) of objects as specified by their primary
keys.
"Class->bulk_insert(\@columns, \@data)"
Adds the given data, an arrayref of arrayrefs containing column values
in the order of column names given in "\@columns", as directly to the
database as "Class" records.
Note that only some database drivers (for example,
"Data::ObjectDriver::Driver::DBD::Pg") implement the bulk insert
operation.
"$obj->fetch_data()"
Returns the current values from $obj as saved in the database, as a
hashref.
"$obj->refresh()"
Resets the values of $obj from the database. Any unsaved modifications
to $obj will be lost, and any made meanwhile will be reflected in $obj
afterward.
"$obj->column_func($column)"
Creates an accessor/mutator method for column $column, returning it as
a coderef.
Override this if you need special behavior in all accessor/mutator
methods.
"$obj->deflate()"
Returns a minimal representation of the object, for use in caches where
you might want to preserve space (like memcached). Can also be
overridden by subclasses to store the optimal representation of an
object in the cache. For example, if you have metadata attached to an
object, you might want to store that in the cache, as well.
"Class->inflate($deflated)"
Inflates the deflated representation of the object $deflated into a
proper object in the class Class. That is, undoes the operation
"$deflated = $obj->deflate()" by returning a new object equivalent to
$obj.
TRANSACTION SUPPORT AND METHODS
Introduction
When dealing with the methods on this class, the transactions are
global, i.e: applied to all drivers. You can still enable transactions
per driver if you directly use the driver API.
"Class->begin_work"
This enable transactions globally for all drivers until the next
rollback or commit call on the class.
If begin_work is called while a transaction is still active (nested
transaction) then the two transactions are merged. So inner
transactions are ignored and a warning will be emitted.
"Class->rollback"
This rollbacks all the transactions since the last begin work, and
exits from the active transaction state.
"Class->commit"
Commits the transactions, and exits from the active transaction state.
"Class->txn_debug"
Just return the value of the global flag and the current working
drivers in a hashref.
"Class->txn_active"
Returns true if a transaction is already active.
DIAGNOSTICS
· "Please specify a valid column for class"
One of the class relationships you defined with "has_a()" was
missing a "column" member.
· "Please define a valid method for column"
One of the class relationships you defined with "has_a()" was
missing its "method" member and a method name could not be
generated, or the class for which you specified the relationship
already has a method by that name. Perhaps you specified an
additional accessor by the same name for that class.
· "keys don't match with primary keys: list"
The hashref of values you passed as the ID to
"primary_key_to_terms()" was missing or had extra members. Perhaps
you used a full "column_values()" hash instead of only including
that class's key fields.
· "You tried to set inexistent column column name to value data on
class name"
The hashref you specified to "set_values()" contained keys that are
not defined columns for that class of object. Perhaps you invoked
it on the wrong class, or did not fully filter members of the hash
out before using it.
· "Cannot find column 'column' for class 'class'"
The column you specified to "column()" does not exist for that
class, you attempted to use an automatically generated
accessor/mutator for a column that doesn't exist, or attempted to
use a column accessor as a class method instead of an instance
method. Perhaps you performed your call on the wrong class or
variable, or misspelled a method or column name.
· "Must specify column"
You invoked the "column_func()" method without specifying a column
name. Column names are required to create the accessor/mutator
function, so it knows what data member of the object to use.
· "number (of partitions) is required"
You attempted to define partitioning for a class without specifying
the number of partitions for that class in the "number" member.
Perhaps your logic for determining the number of partitions
resulted in "undef" or 0.
· "get_driver is required"
You attempted to define partitioning for a class without specifying
the function to find the object driver for a partition ID as the
"get_driver" member.
BUGS AND LIMITATIONS
There are no known bugs in this module.
SEE ALSO
Data::ObjectDriver, Data::ObjectDriver::Driver::DBI,
Data::ObjectDriver::Driver::SimplePartition
LICENSE
Data::ObjectDriver is free software; you may redistribute it and/or
modify it under the same terms as Perl itself.
AUTHOR & COPYRIGHT
Except where otherwise noted, Data::ObjectDriver is Copyright 2005-2006
Six Apart, cpan@sixapart.com. All rights reserved.
perl v5.14.1 2010-03-22 Data::ObjectDriver::BaseObject(3)
