NAME

Lab::Moose::Instrument::Cache - Role for device cache functionality in Moose::Instrument drivers

VERSION

version 3.620

SYNOPSIS

in your driver:

 use Lab::Moose::Instrument::Cache;

 cache foobar => (getter => 'get_foobar');

 sub get_foobar {
     my $self = shift;
     
     return $self->cached_foobar(
         $self->query(command => ...));
 }

 sub set_foobar {
     my ($self, $value) = @_;
     $self->write(command => ...);
     $self->cached_foobar($value);
 }

DESCRIPTION

This package exports a new Moose keyword: cache.

Calling cache key => (getter => $getter, isa => $type) generates the following functions:

cached_key (accessor)

Calling $instr->cached_key() will return the last stored value from the cache. If the cache entry is empty, use the $getter method.

To update the cache entry, call $instr->cached_key($value).

has_cached_key (predicate)

Return true if the cache entry holds a value (which is not undef).

clear_cached_key (clearer)

Clear the value of the cache entry.

cached_key_builder (builder)

Called by cached_key if the entry is cleared. This will call the $getter method. Can be overriden by 'around' method modifier if the $getter needs special extra arguments.

The isa argument is optional.

Array cache

Some methods take an additional parameter (e.g. channel number). For this case you can give the index_arg argument to the cache keyword:

 cache foobar => (isa => 'Num', getter => 'get_foobar', index_arg => 'channel');

 # Get value from cache.
 my $value = $instr->cached_foobar(channel => 1);
 
 # Store value.
 $instr->cached_foobar(channel => 2, value => 1.234);
 
 # Clear single entry.
 $instr->clear_cached_foobar(channel => 3);
 
 # Clear them all.
 $instr->clear_cached_foobar();
 
 # Check for cache value
 if ($instr->has_cached_foobar(channel => 1)) {...}

COPYRIGHT AND LICENSE

This software is copyright (c) 2018 by the Lab::Measurement team; in detail:

  Copyright 2016       Simon Reinhardt
            2017       Andreas K. Huettel, Simon Reinhardt

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.