Peter Seibel > MethodMaker-0.9 > Class::MethodMaker



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Class::MethodMaker - a module for creating generic methods


use Class::MethodMaker new_with_init => 'new', get_set => [ qw /foo bar baz / ];


This module solves the problem of having to write a bazillion get/set methods that are all the same. The argument to 'use' is a hash whose keys are the names of types of generic methods generated by MethodMaker and whose values tell method maker what methods to make. (More precisely, the keys are the names of MethodMaker methods (methods that write methods) and the values are the arguments to those methods.



Creates a basic constructor.

Takes a single string or a reference to an array of strings as its argument. For each string creates a method of the form:

    sub <string> {
      my ($class, @args) = @_;
      my $self = {};
      bless $self, $class;


Creates a basic constructor which calls a method named init after instatiating the object. The init() method should be defined in the class using MethodMaker.

Takes a single string or a reference to an array of strings as its argument. For each string creates a method of the form listed below.

    sub <string> {
      my ($class, @args) = @_;
      my $self = {};
      bless $self, $class;


Creates a basic constructor which accepts a hash of slot-name/value pairs with which to initialize the object. The slot-names are interpreted as the names of methods that can be called on the object after it is created and the values are the arguments to be passed to those methods.

Takes a single string or a reference to an array of strings as its argument. For each string creates a method of the form listed below. Note that this method can be called on an existing objec, which allows it to be combined with new_with_init (see above) to provide some default values. (Basically, declare a new_with_init method, say 'new' and a new_hash_init method, for example, 'hash_init' and then in the init method, you can call modify or add to the %args hash and then call hash_init.)

    sub <string> {
      my ($class, %args) = @_;
      my $self = {};
      bless $self, $class;
      foreach (keys %args) {


Takes a single string or a reference to an array of strings as its argument. For each string, x creates two methods:

  sub x {
    my ($self, $new) = @_;
    defined $new and $self->{$name} = $new;

  sub clear_x
    my ($self) = @_;
    $self->{$name} = undef;

This is your basic get/set method, and can be used for slots containing any scalar value, including references to non-scalar data. Note, however, that MethodMaker has meta-methods that define more useful sets of methods for slots containing references to lists, hashes, and objects.


Like get_set except sets don't clear out the original value, but instead concatenate the new value to the existing one. Thus these slots are only good for plain scalars. Also, like get_set, defines clear_foo method.


Creates get/set methods like get_set but also defines a method which returns a list of the slots in the group.

  fields => {
             group => 'group_name',
             slots => [ qw / slot1 slot2 / ]

Takes a single hash-ref or a reference to an array of hash-refs as its argument. Each hash-ref should have have the keys group and slots. The group value is the name of the method which returns the list of slots and the slots value should be an acceptable argument for get_set.


Creates methods for accessing a slot that contains an object of a given class as well as methods to automatically pass method calls onto the object stored in that slot.

    object => [
               'Foo' => 'phooey',
               'Bar' => [ qw / bar1 bar2 bar3 / ],
               'Baz' => {
                         slot => 'foo',
                         comp_mthds => [ qw / bar baz / ]

This is a hairy one. The main argument should be a reference to an array. The array should contain pairs of class => sub-argument pairs. The sub-argument's are further parsed thusly:

If the sub-argument is a simple string or a reference to an array of strings (as is the case for Foo and Bar above), for each string a get/set method is created that can store an object of that class. (The get/set method, if called with a reference to an object of the given class as the first argument, stores it in the slot. If the slot isn't filled yet it creates an object by calling the given class's new method. Any arguments passed to the get/set method are passed on to new. In all cases the object now stored in the slot is returned.

If the sub-argument is a ref to a hash (as with Baz, above) then the hash should have two keys: slot and comp_mthds. The value indexed by 'slot' will be interpreted as the is in (a). The value or values (ref to an array if plural) indexed by 'comp_mthds' are the names of methods which should be "inherited" from the object stored in the slot. That is, using the example above, a method, foo, is created in the class that calls MethodMaker, which can get and set the value of a slot containing an object of class Baz. Class Baz in turn defines two methods, 'bar', and 'baz'. Two more methods are created in the class using MethodMaker, named 'bar' and 'baz' which result in a call to the 'bar' and 'baz' methods, through the Baz object stored in slot foo.


  boolean => [ qw / foo bar baz / ]

Creates methods for setting, checking and clearing flags. All flags created with this meta-method are stored in a single vector for space efficiency. The argument to boolean should be a string or a reference to an array of strings. For each string x it defines several methods: x, set_x, and clear x. x returns the value of the x-flag. If called with an argument, it first sets the x-flag to the truth-value of the argument. set_x is equivalent to x(1) and clear_x is equivalent to x(0).

Additionally, boolean defines three class method: bits, which returns the vector containing all of the bit fields (remember however that a vector containing all 0 bits is still true), boolean_fields, which returns a list of all the flags by name, and bit_dump, which returns a hash of the flag-name/flag-value pairs.


  listed_attrib => [ qw / foo bar baz / ]

Like boolean, listed_attrib creates x, set_x, and clear_x methods. However, it also defines a class method x_objects which returns a list of the objects which presently have the x-flag set to true. N.B. listed_attrib does not use the same space efficient implementation as boolean, so boolean should be prefered unless the x_objects method is actually needed.


  key_attrib => [ qw / foo bar baz / ]

Creates get/set methods like get/set but also maintains a hash in which each object is stored under the value of the field when the slot is set. If an object has a slot set to a value which another object is already set to the object currently set to that value has that slot set to undef and the new object will be put into the hash under that value. (I.e. only one object can have a given key. The method find_x is defined which if called with any arguments returns a list of the objects stored under those values in the hash. Called with no arguments, it returns a reference to the hash.


  key_with_create => [ qw / foo bar baz / ]

Just like key_attrib except the find_x method is defined to call the new method to create an object if there is no object already stored under any of the keys you give as arguments.


Creates several methods for dealing with slots containing list data. Takes a string or a reference to an array of strings as its argument and for each string, x, creates the methods: x, push_x, and pop_x. The method x returns the list of values stored in the slot. In an array context it returns them as an array and in a scalar context as a reference to the array. If called with arguments, x will push them onto the list. push_x and pop_x do about what you would expect.


Creates a group of methods for dealing with hash data stored in a slot. Takes a string or a reference to an array of strings and for each string, x, creates: x, x_keys, x_values, and x_tally. Called with no arguments x returns the hash stored in the slot, as a hash in an array context or as a refernce in a scalar context. Called with one argument it treats the argument as a key and returns the value stored under that key, or as a list of keys (if it is a reference to a list) and returns the list of values stored under those keys. Called with more than one argument, treats them as a series of key/value pairs and adds them to the hash. x_keys returns the keys of the hash, and x_values returns the list of values. x_tally takes a list of arguments and for each scalar in the list increments the value stored in the hash and returns a list of the current (after the increment) values.


  code => [ qw / foo bar baz / ]

Creates a slot that holds a code reference. Takes a string or a reference to a list of string and for each string, x, creates a method x which if called with one argument which is a CODE reference, it installs that code in the slot. Otherwise it runs the code stored in the slot with whatever arguments (including none) were passed in.


  method => [ qw / foo bar baz / ]

Just like code, except the code is called like a method, with $self as it's first argument. Basically, you're creating a method which can be different for each object. Which is sort of weird. But perhaps useful.

  interface => [ qw / foo bar baz / ]


MethodMaker is a class that can be inherited. A subclass can define new method types by writing a method that returns a hash of method_name/code-reference pairs.

For example a simple sub-class that defines a method type upper_case_get_set might look like this:

  package Class::MethodMakerSubclass;

  use strict;
  use Class::MethodMaker;

  @Class::MethodMakerSubclass::ISA = qw ( Class::MethodMaker );

  sub upper_case_get_set {
    shift; # we don't need the class name
    my ($name) = @_;
    my %results;
    $results{$name} =
      sub {
        my ($self, $new) = @_;
        defined $new and $self->{$name} = uc $new;


Class::MethodMaker v0.9

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