Chapter 3

Now to set values in the hash, a two argument form of the accessor is used:

# heading at (10,20,100) at 50 kph

$probe >heading(x     => 10);

$probe >heading(y     => 20);

$probe >heading(z     => 100);

$probe >heading(speed => 50);

There are some limitations to using Class::Struct. First, it can't be used to 

create child classes. Class::Struct goes to some truly amazing lengths to prevent 

this.

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 Second, if you need to do anything interesting when the constructor gets 

called, you'll need to write your own new().

Using Class::MethodMaker

When Class::Struct isn't enough, Class::MethodMaker

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 comes to the rescue. 

Class::MethodMaker supports all the same functionality as Class::Struct and a 

whole lot more. Class::MethodMaker can generate a wide variety of accessors that 

cover not only object methods, but also useful class methods. I'll cover the basic 

functionality, but you'll need to read the module documentation to discover the 

more esoteric bits. There's a lot in there!

Class::MethodMaker differs from Class::Struct in that you don't just tell it what 

kind of data you'll be storing in your attributes; you also get to pick what kind of 

accessor to provide. This also applies to the constructor, which Class::Struct doesn't 

even let you name! Here's an example of using Class::MethodMaker to generate 

some simple scalar accessor mutators and a constructor called new():

package BOA::Probe;

use Class::MethodMaker

   new     =>  new ,

   get_set => [ qw(id model contents heading status) ];

Class::MethodMaker works by taking arguments to the use statement in key value 

pairs. The key is a method in the Class::MethodMaker module, and the value is 

either a single string or a reference to an array of strings. These strings are the 

names of the methods to be created. After the preceding call, the eleven methods 

are created two for each of the five attributes given for the get_set key and new().

The two methods created for each get_set attribute are a normal accessor 

mutator for the attribute and a method to clear the attribute called clear_id(),

10. Class::Struct ties your @ISA to a private class that croaks on STORE()! How rude.

11. Available on CPAN. Class::MethodMaker was written by Peter Seibel and is being refurbished 

and maintained by Martyn J. Pierce.

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