NAME
Resource::Loader - Load different resources depending...
SYNOPSIS
use Resource::Loader;
$loader = Resource::Loader->new(
testing => 0,
verbose => 0,
cont => 0,
resources =>
[
{ name => 'never',
when => sub { 0 },
what => sub { die "this will never be loaded" },
},
{ name => 'sometimes 50%',
when => sub { int rand 2 > 0 },
what => sub { "'sometimes' was loaded. args: [@_]" },
whatargs => [ qw/foo bar baz/ ],
},
{ name => 'sometimes 66%',
when => sub { int rand @_ },
whenargs => [ 0, 1, 2 ],
what => sub { "'sometimes' was loaded. args: [@_]" },
whatargs => [ qw/foo bar baz/ ],
},
{ name => 'always',
when => sub { 1 },
what => sub { "always' was loaded" },
},
],
);
$loaded = $loader->load;
$status = $loader->status;
DESCRIPTION
Resource::Loader is simple at its core: You give it a list of resources.
Each resource knows when it should be triggered and if it's triggered,
will run its code segment.
Both the *when* and the *what* are coderefs, so you can be as devious as
you want in determining when a resource will be loaded and what,
exactly, it does.
I originally wrote this to solve a simple problem but realized that the
class is probably applicable to a whole slew of problems. I look forward
to hearing to what devious ends you push this module. Really, send me an
email - I love hearing about people using my toys.
Want to know what my 'simple problem' was? See the EXAMPLES.
METHODS
new()
Create a new object.
$loader = Resource::Loader->new(
testing => 0,
verbose => 0,
cont => 0,
resources =>
[
{ name => 'never',
when => sub { 0 },
what => sub { die "this will never be loaded" },
},
{ name => 'sometimes 50%',
when => sub { int rand 2 > 0 },
what => sub { "'sometimes' was loaded. args: [@_]" },
whatargs => [ qw/foo bar baz/ ],
},
{ name => 'sometimes 66%',
when => sub { int rand @_ },
whenargs => [ 0, 1, 2 ],
what => sub { "'sometimes' was loaded. args: [@_]" },
whatargs => [ qw/foo bar baz/ ],
},
{ name => 'always',
when => sub { 1 },
what => sub { "always' was loaded" },
},
],
);
Note: *testing*, *verbose*, *cont* all default to zero.
resources()
What to run and when to run it.
# arrayref style
$loader->resources(
[
{ name => 'never',
when => sub { 0 },
what => sub { die "this will never be loaded" },
},
{ name => 'sometimes 50%',
when => sub { int rand 2 > 0 },
what => sub { "'sometimes' was loaded. args: [@_]" },
whatargs => [ qw/foo bar baz/ ],
},
{ name => 'sometimes 66%',
when => sub { int rand @_ },
whenargs => [ 0, 1, 2 ],
what => sub { "'sometimes' was loaded. args: [@_]" },
whatargs => [ qw/foo bar baz/ ],
},
{ name => 'always',
when => sub { 1 },
what => sub { "always' was loaded" },
}
]
);
# list style
$loader->resources(
{ name => 'never',
when => sub { 0 },
what => sub { die "this will never be loaded" },
},
{ name => 'sometimes 50%',
when => sub { int rand 2 > 0 },
what => sub { "'sometimes' was loaded. args: [@_]" },
whatargs => [ qw/foo bar baz/ ],
},
{ name => 'sometimes 66%',
when => sub { int rand @_ },
whenargs => [ 0, 1, 2 ],
what => sub { "'sometimes' was loaded. args: [@_]" },
whatargs => [ qw/foo bar baz/ ],
},
{ name => 'always',
when => sub { 1 },
what => sub { "always' was loaded" },
}
);
Each resource is a hashref that takes the same arguments:
name what is this resource called?
when a coderef that controls whether the resource will be activated
whenargs an optional arrayref of arguments that are passed to the
*when*.
what a coderef that is only run if the *when* coderef returns true
whatargs an optional arrayref of arguments that are passed to the
*what*.
Note: using colons in your *name*s is not recommended. It will break the
$ENV{RMSTATES} handling. Keep It Simple.
load()
$loaded = $loader->load;
Load the resources.
Walks through the resources() in order. For each resource, if the *when*
coderef returns true, then the *what* coderef will be run as well.
That behaviour can be changed with the cont() and testing() methods as
well as the analagous *RMCONT* and *RMTESTING* environment variables.
load() returns the output of loaded(); a hashref of *name*s that loaded
successfully and the respective return values.
Note: Running this method will overwrite any preexisting status() and
loaded() tables with current info.
Note: Don't confuse this with loaded(). load() loads the resources,
loaded() tells you what loaded.
cont()
$will_continue = $loader->cont( 1 );
$will_continue = $loader->cont( 0 ); # default
$will_continue = $loader->cont;
Do you want to continue loading resources after the first one is loaded?
Sometimes you want the first successful resource to load and then skip
all the others. That's the default behaviour. If you set cont() to 1,
then load() will keep checking (and loading resources).
When true, all states with true *when* coderefs will be loaded.
When false, execution of states will stop after the first. (default)
The *RMCONT* environment variable value takes precedence to any value
that this method is set to.
cont() will return true if either *$ENV{RMCONT}* or this method has been
set to true.
testing()
$is_testing = $loader->testing( 1 );
$is_testing = $loader->testing( 0 ); # default
$is_testing = $loader->testing;
When true, don't actually run the *what* resources.
When false, it will.
The *RMTESTING* environment variable value takes precedence to any value
that this is set to. It will return true if either *$ENV{RMTESTING}* or
this method has been set to true.
When testing() is on, status() results will be set to *skipped* if the
*when* coderef if true but the *what* coderef wasn't run.
verbose()
$is_verbose = $loader->verbose( 1 );
$is_verbose = $loader->verbose( 0 ); # default
$is_verbose = $loader->verbose;
When true, print internal processing messages to STDOUT
When false, run quietly.
The *RMVERBOSE* environment variable value takes precedence to any value
that this is set to. It will return true if either *$ENV{RMVERBOSE}* or
this method has been set to true.
status()
$status = $loader->status;
Returns a hashref of which resources loading stati. Maps *name*s to one
of these values: Don't forget to call load() first!
loaded The *when* succeeded so *what* was run
skipped *$ENV{RMSTATES}* is defined but this state *name* wasn't isn't
in it so neither *when* nor *what* was run
notrun *when* succeeded and but *what* wasn't run because we're in
testing mode.
inactive *what* wasn't run.
loaded()
$loaded = $loader->loaded;
Returns a hashref that maps state *name*s to the return values of loaded
resources.
Note: Don't confuse this with load(). load() loads the resources,
loaded() tells you what loaded.
env()
$env = $loader->env;
Returns a hashref of the Resource::Loader-related environment variables
and their current values. Probably only useful for debugging.
ENVIRONMENT
Use these environment variables to override the local behavior of the
object (e.g. to test your Resource::Loader's responses)
RMSTATES
Colon-separated list of states to run resources for. The *when* coderefs
won't even be run if the state *name*s aren't listed here.
RMCONT
See cont()
RMTESTING
See testing()
RMVERBOSE
See verbose()
EXAMPLES
I originally wrote this to handle our software deployment needs. The
software starts its life on our development machine. From there, it's
pushed to a test machine. If it tests clean there, we pushed it to one
or more production machine(s). The test and production machines are
supposed to be as similar as possible to prevent surprises when the
software hits production.
We don't want to mix environments by, say, testing code on the dev box
with the production database. Accidentally mangling a production
database would be, how you say, dumb.
The source code for this is in the examples/ directory.
There are other examples in that directory, check them out!
SEE ALSO
Abstract Factory design pattern. This isn't a factory but it's similar.
AUTHOR
Joshua Keroes, <skunkworks@eli.net>
COPYRIGHT AND LICENSE
Copyright 2003 by Joshua Keroes
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.