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Manual Reference Pages  -  CLASS::MAKEMETHODS::STANDARD::ARRAY (3)

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NAME

Class::MakeMethods::Standard::Array - Methods for Array objects

CONTENTS

SYNOPSIS



  package MyObject;
  use Class::MakeMethods::Standard::Array (
    new => new,
    scalar => [ foo, bar ],
    array => my_list,
    hash => my_index,
  );
  ...
 
  my $obj = MyObject->new( foo => Foozle );
  print $obj->foo();
 
  $obj->bar(Barbados);
  print $obj->bar();
 
  $obj->my_list(0 => Foozle, 1 => Bang!);
  print $obj->my_list(1);
 
  $obj->my_index(broccoli => Blah!, foo => Fiddle);
  print $obj->my_index(foo);



DESCRIPTION

The Standard::Array suclass of MakeMethods provides a basic constructor and accessors for blessed-array object instances.

    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.

Positional Accessors and CW%FIELDS

Each accessor method is assigned the next available array index at which to store its value.

The mapping between method names and array positions is stored in a hash named %FIELDS in the declaring package. When a package declares its first positional accessor, its %FIELDS are initialized by searching its inheritance tree.

<B>WarningB>: Subclassing packages that use positional accessors is somewhat fragile, since you may end up with two distinct methods assigned to the same position. Specific cases to avoid are:
o If you inherit from more than one class with positional accessors, the positions used by the two sets of methods will overlap.
o If your superclass adds additional positional accessors after you declare your first, they will overlap yours.

METHOD GENERATOR TYPES

    new - Constructor

For each method name passed, returns a subroutine with the following characteristics:
o Has a reference to a sample item to copy. This defaults to a reference to an empty array, but you may override this with the defaults = array_ref> method parameter.
o If called as a class method, makes a new array containing values from the sample item, and blesses it into that class.
o If called on an array-based instance, makes a copy of it and blesses the copy into the same class as the original instance.
o If passed a list of method-value pairs, calls each named method with the associated value as an argument.
o Returns the new instance.
Sample declaration and usage:



  package MyObject;
  use Class::MakeMethods::Standard::Array (
    new => new,
  );
  ...
 
  # Bare constructor
  my $empty = MyObject->new();
 
  # Constructor with initial sequence of method calls
  my $obj = MyObject->new( foo => Foozle, bar => Barbados );
 
  # Copy with overriding sequence of method calls
  my $copy = $obj->new( bar => Bob );



    scalar - Instance Accessor

For each method name passed, uses a closure to generate a subroutine with the following characteristics:
o Must be called on an array-based instance.
o Determines the array position associated with the method name, and uses that as an index into each instance to access the related value. This defaults to the next available slot in %FIELDS, but you may override this with the array_index = number> method parameter, or by pre-filling the contents of %FIELDS.
o If called without any arguments returns the current value (or undef).
o If called with an argument, stores that as the value, and returns it,
Sample declaration and usage:



  package MyObject;
  use Class::MakeMethods::Standard::Array (
    scalar => foo,
  );
  ...
 
  # Store value
  $obj->foo(Foozle);
 
  # Retrieve value
  print $obj->foo;



    array - Instance Ref Accessor

For each method name passed, uses a closure to generate a subroutine with the following characteristics:
o Must be called on an array-based instance.
o Determines the array position associated with the method name, and uses that as an index into each instance to access the related value. This defaults to the next available slot in %FIELDS, but you may override this with the array_index = number> method parameter, or by pre-filling the contents of %FIELDS.
o The value for each instance will be a reference to an array (or undef).
o If called without any arguments, returns the current array-ref value (or undef).
o If called with a single non-ref argument, uses that argument as an index to retrieve from the referenced array, and returns that value (or undef).
o If called with a single array ref argument, uses that list to return a slice of the referenced array.
o 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 instance’s 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.
o 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 MyObject;
  use Class::MakeMethods::Standard::Array (
    array => bar,
  );
  ...
 
  # Clear and set contents of list
  print $obj->bar([ Spume, Frost ] ); 
 
  # Set values by position
  $obj->bar(0 => Foozle, 1 => Bang!);
 
  # Positions may be overwritten, and in any order
  $obj->bar(2 => And Mash, 1 => Blah!);
 
  # Retrieve value by position
  print $obj->bar(1);
 
  # Direct access to referenced array
  print scalar @{ $obj->bar() };



There are also calling conventions for slice and splice operations:



  # Retrieve slice of values by position
  print join(, , $obj->bar( undef, [0, 2] ) );
 
  # Insert an item at position in the array
  $obj->bar([3], Potatoes ); 
 
  # Remove 1 item from position 3 in the array
  $obj->bar([3, 1], undef ); 
 
  # Set a new value at position 2, and return the old value
  print $obj->bar([2, 1], Froth );



    hash - Instance Ref Accessor

For each method name passed, uses a closure to generate a subroutine with the following characteristics:
o Must be called on an array-based instance.
o Determines the array position associated with the method name, and uses that as an index into each instance to access the related value. This defaults to the next available slot in %FIELDS, but you may override this with the array_index = number> method parameter, or by pre-filling the contents of %FIELDS.
o The value for each instance will be a reference to a hash (or undef).
o If called without any arguments, returns the contents of the hash in list context, or a hash reference in scalar context (or undef).
o If called with one argument, uses that argument as an index to retrieve from the referenced hash, and returns that value (or undef). If the single argument is an array ref, then a slice of the referenced hash is returned.
o If called with a list of key-value pairs, stores the value under the given key in the referenced hash. If the instance’s value was previously undefined, a new hash is autovivified. 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 MyObject;
  use Class::MakeMethods::Standard::Array (
    hash => baz,
  );
  ...
 
  # Set values by key
  $obj->baz(foo => Foozle, bar => Bang!);
 
  # Values may be overwritten, and in any order
  $obj->baz(broccoli => Blah!, foo => Fiddle);
 
  # Retrieve value by key
  print $obj->baz(foo);
 
  # Retrive slice of values by position
  print join(, , $obj->baz( [foo, bar] ) );
 
  # Direct access to referenced hash
  print keys %{ $obj->baz() };
 
  # Reset the hash contents to empty
  @{ $obj->baz() } = ();



    object - Instance Ref Accessor

For each method name passed, uses a closure to generate a subroutine with the following characteristics:
o Must be called on an array-based instance.
o Determines the array position associated with the method name, and uses that as an index into each instance to access the related value. This defaults to the next available slot in %FIELDS, but you may override this with the array_index = number> method parameter, or by pre-filling the contents of %FIELDS.
o The value for each instance will be a reference to an object (or undef).
o If called without any arguments returns the current value.
o If called with an argument, stores that as the value, and returns it,
Sample declaration and usage:



  package MyObject;
  use Class::MakeMethods::Standard::Hash (
    object => foo,
  );
  ...
 
  # Store value
  $obj->foo( Foozle->new() );
 
  # Retrieve value
  print $obj->foo;



SEE ALSO

See Class::MakeMethods for general information about this distribution.

See Class::MakeMethods::Standard for more about this family of subclasses.

See Class::MakeMethods::Standard::Hash for equivalent functionality based on blessed hashes. If your module will be extensively subclassed, consider switching to Standard::Hash to avoid the subclassing concerns described above.

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perl v5.20.3 MAKEMETHODS::STANDARD::ARRAY (3) 2004-09-06

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