One example might be you have a Backend class where your app sends all its data. You might instantiate the backend object like this:

my $backend = Backend->new();
Role::Tiny->apply_roles_to_object(
  $backend,
  qw( Backend::Storage::PostgreSQL Backend::Log::Debug Backend::Interf
+ace::TCP ),
);

[download]

And now your backend object will store its data in PostgreSQL, and spit out debugging information to its log file, and listen on a TCP port for instructions.

If you have eight different possibilities for storage (different types of database, XML files, JSON files, etc), 4 different options for logging, and 4 different interfaces (TCP, Unix Sockets, Command Line, and HTTP), that gives 128 possible combinations. You don't really want to have to create classes for Backend::PostgreSQL_Debugging_TCP, Backend::MySQL_Debugging_TCP, Backend::PostgreSQL_Debugging_HTTP, etc. Instead you just compose the combination of roles you want.

(In this particular example, there's an argument for making more use of delegation instead of composition, but I digress.)

toby döt ink

In reply to Re: Role::Tiny: When to use apply_roles_to_object? by tobyink
in thread Role::Tiny: When to use apply_roles_to_object? by karlgoethebier

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