NAME¶
Class::MakeMethods::Standard::Inheritable - Overridable data
SYNOPSIS¶
package MyClass;
use Class::MakeMethods( 'Standard::Inheritable:scalar' => 'foo' );
# We now have an accessor method for an "inheritable" scalar value
MyClass->foo( 'Foozle' ); # Set a class-wide value
print MyClass->foo(); # Retrieve class-wide value
my $obj = MyClass->new(...);
print $obj->foo(); # All instances "inherit" that value...
$obj->foo( 'Foible' ); # until you set a value for an instance.
print $obj->foo(); # This now finds object-specific value.
...
package MySubClass;
@ISA = 'MyClass';
print MySubClass->foo(); # Intially same as superclass,
MySubClass->foo('Foobar'); # but overridable per subclass,
print $subclass_obj->foo(); # and shared by its instances
$subclass_obj->foo('Fosil');# until you override them...
...
# Similar behaviour for hashes and arrays is currently incomplete
package MyClass;
use Class::MakeMethods::Standard::Inheritable (
array => 'my_list',
hash => 'my_index',
);
MyClass->my_list(0 => 'Foozle', 1 => 'Bang!');
print MyClass->my_list(1);
MyClass->my_index('broccoli' => 'Blah!', 'foo' => 'Fiddle');
print MyClass->my_index('foo');
DESCRIPTION¶
The MakeMethods subclass provides accessor methods that search an inheritance
tree to find a value. This allows you to set a shared or default value for a
given class, optionally override it in a subclass, and then optionally
override it on a per-instance basis.
Note that all MakeMethods methods are inheritable, in the sense that they work
as expected for subclasses. These methods are different in that the
data accessed by each method can be inherited or overridden in each
subclass or instance. See "
Class::MakeMethods::Utility::Inheritable" for more about this type of
"inheritable" or overridable" data.
Calling Conventions¶
When you "use" this package, the method names you provide as arguments
cause subroutines to be generated and installed in your module.
See "Calling Conventions" in Class::MakeMethods::Standard for more
information.
Declaration Syntax¶
To declare methods, pass in pairs of a method-type name followed by one or more
method names.
Valid method-type names for this package are listed in "METHOD GENERATOR
TYPES".
See "Declaration Syntax" in Class::MakeMethods::Standard and
"Parameter Syntax" in Class::MakeMethods::Standard for more
information.
METHOD GENERATOR TYPES¶
scalar - Class-specific Accessor¶
For each method name passed, uses a closure to generate a subroutine with the
following characteristics:
- •
- May be called as a class or instance method, on the declaring class or any
subclass.
- •
- If called without any arguments returns the current value for the callee.
If the callee has not had a value defined for this method, searches up
from instance to class, and from class to superclass, until a callee with
a value is located.
- •
- If called with an argument, stores that as the value associated with the
callee, whether instance or class, and returns it,
Sample declaration and usage:
package MyClass;
use Class::MakeMethods::Standard::Inheritable (
scalar => 'foo',
);
...
# Store value
MyClass->foo('Foozle');
# Retrieve value
print MyClass->foo;
array - Class-specific Ref Accessor¶
For each method name passed, uses a closure to generate a subroutine with the
following characteristics:
- •
- May be called as a class method, or on any instance or subclass, Must be
called on a hash-based instance.
- •
- The class value will be a reference to an array (or undef).
- •
- If called without any arguments, returns the contents of the array in list
context, or an array reference in scalar context (or undef).
- •
- If called with a single array ref argument, sets the contents of the array
to match the contents of the provided one.
- •
- If called with a single numeric argument, uses that argument as an index
to retrieve from the referenced array, and returns that value (or
undef).
- •
- If called with a two arguments, the first undefined and the second an
array ref argument, uses that array's contents as a list of indexes to
return a slice of the referenced array.
- •
- If called with a list of argument pairs, each with a non-ref index and an
associated value, stores the value at the given index in the referenced
array. If the class value was previously undefined, a new array is
autovivified. The current value in each position will be overwritten, and
later arguments with the same index will override earlier ones. Returns
the current array-ref value.
- •
- If called with a list of argument pairs, each with the first item being a
reference to an array of up to two numbers, loops over each pair and uses
those numbers to splice the value array.
The first controlling number is the position at which the splice will begin.
Zero will start before the first item in the list. Negative numbers count
backwards from the end of the array.
The second number is the number of items to be removed from the list. If it
is omitted, or undefined, or zero, no items are removed. If it is a
positive integer, that many items will be returned.
If both numbers are omitted, or are both undefined, they default to
containing the entire value array.
If the second argument is undef, no values will be inserted; if it is a
non-reference value, that one value will be inserted; if it is an
array-ref, its values will be copied.
The method returns the items that removed from the array, if any.
Sample declaration and usage:
package MyClass;
use Class::MakeMethods::Standard::Inheritable (
array => 'bar',
);
...
# Clear and set contents of list
print MyClass->bar([ 'Spume', 'Frost' ] );
# Set values by position
MyClass->bar(0 => 'Foozle', 1 => 'Bang!');
# Positions may be overwritten, and in any order
MyClass->bar(2 => 'And Mash', 1 => 'Blah!');
# Retrieve value by position
print MyClass->bar(1);
# Direct access to referenced array
print scalar @{ MyClass->bar() };
There are also calling conventions for slice and splice operations:
# Retrieve slice of values by position
print join(', ', MyClass->bar( undef, [0, 2] ) );
# Insert an item at position in the array
MyClass->bar([3], 'Potatoes' );
# Remove 1 item from position 3 in the array
MyClass->bar([3, 1], undef );
# Set a new value at position 2, and return the old value
print MyClass->bar([2, 1], 'Froth' );
hash - Class-specific Ref Accessor¶
For each method name passed, uses a closure to generate a subroutine with the
following characteristics:
- •
- May be called as a class method, or on any instance or subclass, Must be
called on a hash-based instance.
- •
- The class value will be a reference to a hash (or undef).
- •
- If called without any arguments, returns the contents of the hash in list
context, or a hash reference in scalar context. If the callee has not had
a value defined for this method, searches up from instance to class, and
from class to superclass, until a callee with a value is located.
- •
- If called with one non-ref argument, uses that argument as an index to
retrieve from the referenced hash, and returns that value (or undef). If
the callee has not had a value defined for this method, searches up from
instance to class, and from class to superclass, until a callee with a
value is located.
- •
- If called with one array-ref argument, uses the contents of that array to
retrieve a slice of the referenced hash. If the callee has not had a value
defined for this method, searches up from instance to class, and from
class to superclass, until a callee with a value is located.
- •
- If called with one hash-ref argument, sets the contents of the referenced
hash to match that provided.
- •
- If called with a list of key-value pairs, stores the value under the given
key in the hash associated with the callee, whether instance or class. If
the callee did not previously have a hash-ref value associated with it,
searches up instance to class, and from class to superclass, until a
callee with a value is located, and copies that hash before making the
assignments. The current value under each key will be overwritten, and
later arguments with the same key will override earlier ones. Returns the
contents of the hash in list context, or a hash reference in scalar
context.
Sample declaration and usage:
package MyClass;
use Class::MakeMethods::Standard::Inheritable (
hash => 'baz',
);
...
# Set values by key
MyClass->baz('foo' => 'Foozle', 'bar' => 'Bang!');
# Values may be overwritten, and in any order
MyClass->baz('broccoli' => 'Blah!', 'foo' => 'Fiddle');
# Retrieve value by key
print MyClass->baz('foo');
# Retrive slice of values by position
print join(', ', MyClass->baz( ['foo', 'bar'] ) );
# Direct access to referenced hash
print keys %{ MyClass->baz() };
# Reset the hash contents to empty
@{ MyClass->baz() } = ();
NOTE: THIS METHOD GENERATOR IS INCOMPLETE.
object - Class-specific Ref Accessor¶
For each method name passed, uses a closure to generate a subroutine with the
following characteristics:
- •
- May be called as a class method, or on any instance or subclass, Must be
called on a hash-based instance.
- •
- The class value will be a reference to an object (or undef).
- •
- If called without any arguments returns the current value for the callee.
If the callee has not had a value defined for this method, searches up
from instance to class, and from class to superclass, until a callee with
a value is located.
- •
- If called with an argument, stores that as the value associated with the
callee, whether instance or class, and returns it,
Sample declaration and usage:
package MyClass;
use Class::MakeMethods::Standard::Inheritable (
object => 'foo',
);
...
# Store value
MyClass->foo( Foozle->new() );
# Retrieve value
print MyClass->foo;
NOTE: THIS METHOD GENERATOR HAS NOT BEEN WRITTEN YET.
SEE ALSO¶
See Class::MakeMethods for general information about this distribution.
See Class::MakeMethods::Standard for more about this family of subclasses.