appconfig::state(3)

NAME

AppConfig::State - Perl5 module for maintaining the state
of an application configuration.

SYNOPSIS

use AppConfig::State;
my $state = AppConfig::State->new(cfg);
$state->define("foo");            # very simple  variable definition
$state->define("bar",  varcfg);   #  variable specific
configuration
$state->define("foo|bar=i@");     # compact format
$state->set("foo", 123);           #  trivial  set/get
examples
$state->get("foo");
$state->foo();                     # shortcut variable
access
$state->foo(456);                 # shortcut  variable
update

OVERVIEW

AppConfig::State is a Perl5 module to handle global con
figuration variables for perl programs. It maintains the
state of any number of variables, handling default values,
aliasing, validation, update callbacks and option argu
ments for use by other AppConfig::* modules.

AppConfig::State is distributed as part of the AppConfig
bundle.

DESCRIPTION

USING THE AppConfig::State MODULE

To import and use the AppConfig::State module the follow ing line should appear in your Perl script:: use AppConfig::State;
The AppConfig::State module is loaded automatically by the new() constructor of the AppConfig module.
AppConfig::State is implemented using object-oriented methods. A new AppConfig::State object is created and initialised using the new() method. This returns a refer ence to a new AppConfig::State object.: my $state = AppConfig::State->new();
This will create a reference to a new AppConfig::State with all configuration options set to their default val ues. You can initialise the object by passing a reference to a hash array containing configuration options:: $state = AppConfig::State->new( {
CASE => 1,
ERROR => my_error,; } );
The new() constructor of the AppConfig module automati cally passes all parameters to the AppConfig::State new() constructor. Thus, any global configuration values and variable definitions for AppConfig::State are also appli cable to AppConfig.
The following configuration options may be specified.
CASE: Determines if the variable names are treated case sen
sitively. Any non-zero value makes case significant
when naming variables. By default, CASE is set to 0
and thus "Variable", "VARIABLE" and "VaRiAbLe" are all
treated as "variable".
CREATE: By default, CREATE is turned off meaning that all
variables accessed via set() (which includes access
via shortcut such as "$state->variable($value)" which
delegates to set()) must previously have been defined
via define(). When CREATE is set to 1, calling
set($variable, $value) on a variable that doesn't
exist will cause it to be created automatically.; When CREATE is set to any other non-zero value, it is
assumed to be a regular expression pattern. If the
variable name matches the regex, the variable is cre
ated. This can be used to specify configuration file
blocks in which variables should be created, for exam
ple:

$state = AppConfig::State->new( {
CREATE => '^define_',

} );; In a config file:

[define]
name = fred # define_name gets created

automatically

[other]
name = john # other_name doesn't - warn

ing raised; Note that a regex pattern specified in CREATE is
applied to the real variable name rather than any
alias by which the variables may be accessed.
PEDANTIC: The PEDANTIC option determines what action the config
uration file (AppConfig::File) or argument parser
(AppConfig::Args) should take on encountering a warn
ing condition (typically caused when trying to set an
undeclared variable). If PEDANTIC is set to any true
value, the parsing methods will immediately return a
value of 0 on encountering such a condition. If
PEDANTIC is not set, the method will continue to parse
the remainder of the current file(s) or arguments,
returning 0 when complete.; If no warnings or errors are encountered, the method
returns 1.; In the case of a system error (e.g. unable to open a
file), the method returns undef immediately, regard
less of the PEDANTIC option.
ERROR: Specifies a user-defined error handling routine. When
the handler is called, a format string is passed as
the first parameter, followed by any additional val
ues, as per printf(3C).
DEBUG: Turns debugging on or off when set to 1 or 0 accord
ingly. Debugging may also be activated by calling
_debug() as an object method ("$state->_debug(1)") or as a package function (AppConfig::State::_debug(1)),
passing in a true/false value to set the debugging
state accordingly. The package variable $AppCon
fig::State::DEBUG can also be set directly.; The _debug() method returns the current debug value. If a new value is passed in, the internal value is
updated, but the previous value is returned.; Note that any AppConfig::File or App::Config::Args
objects that are instantiated with a reference to an
App::State will inherit the DEBUG (and also PEDANTIC)
values of the state at that time. Subsequent changes
to the AppConfig::State debug value will not affect
them.
GLOBAL: The GLOBAL option allows default values to be set for
the DEFAULT, ARGCOUNT, EXPAND, VALIDATE and ACTION
options for any subsequently defined variables.

$state = AppConfig::State->new({
GLOBAL => {
DEFAULT => '<undef>', # default value

for new vars
ARGCOUNT => 1, # vars expect

an argument
ACTION => my_set_var, # callback when

vars get set

}

});; Any attributes specified explicitly when a variable is
defined will override any GLOBAL values.; See "DEFINING VARIABLES" below which describes these
options in detail.
DEFINING VARIABLES
The "define()" function is used to pre-declare a variable and specify its configuration.: $state->define("foo");
In the simple example above, a new variable called "foo" is defined. A reference to a hash array may also be passed to specify configuration information for the vari able:: $state->define("foo", {
DEFAULT => 99,
ALIAS => 'metavar1',; });
Any variable-wide GLOBAL values passed to the new() con structor in the configuration hash will also be applied. Values explicitly specified in a variable's define() con figuration will override the respective GLOBAL values.
The following configuration options may be specified
DEFAULT: The DEFAULT value is used to initialise the variable.

$state->define("drink", {
DEFAULT => 'coffee',

});; print $state->drink(); # prints "coffee"
ALIAS: The ALIAS option allows a number of alternative names
to be specified for this variable. A single alias
should be specified as a string. Multiple aliases can
be specified as a reference to an array of alterna
tives or as a string of names separated by vertical
bars, '|'. e.g.:

$state->define("name", {
ALIAS => 'person',

});; or
$state->define("name", {
ALIAS => [ 'person', 'user', 'uid' ],

});; or
$state->define("name", {
ALIAS => 'person|user|uid',

});; $state->user('abw'); # equivalent to; $state->name('abw');
ARGCOUNT: The ARGCOUNT option specifies the number of arguments
that should be supplied for this variable. By
default, no additional arguments are expected for
variables (ARGCOUNT_NONE).; The ARGCOUNT_* constants can be imported from the App
Config module:

use AppConfig ':argcount';

$state->define('foo', { ARGCOUNT => ARGCOUNT_ONE

});; or can be accessed directly from the AppConfig pack
age:

use AppConfig;

$state->define('foo', { ARGCOUNT => AppCon

fig::ARGCOUNT_ONE });; The following values for ARGCOUNT may be specified.; ARGCOUNT_NONE (0)
Indicates that no additional arguments are
expected. If the variable is identified in a con
firguration file or in the command line arguments,
it is set to a value of 1 regardless of whatever
arguments follow it.; ARGCOUNT_ONE (1)
Indicates that the variable expects a single argu
ment to be provided. The variable value will be
overwritten with a new value each time it is
encountered.; ARGCOUNT_LIST (2)
Indicates that the variable expects multiple
arguments. The variable value will be appended to
the list of previous values each time it is
encountered.; ARGCOUNT_HASH (3)
Indicates that the variable expects multiple argu
ments and that each argument is of the form
"key=value". The argument will be split into a
key/value pair and inserted into the hash of val
ues each time it is encountered.
ARGS: The ARGS option can also be used to specify advanced
command line options for use with AppConfig::Getopt,
which itself delegates to Getopt::Long. See those two
modules for more information on the format and meaning
of these options.

$state->define("name", {
ARGS => "=i@",

});
EXPAND: The EXPAND option specifies how the AppConfig::File
processor should expand embedded variables in the con
figuration file values it reads. By default, EXPAND
is turned off (EXPAND_NONE) and no expansion is made.; The EXPAND_* constants can be imported from the App
Config module:

use AppConfig ':expand';

$state->define('foo', { EXPAND => EXPAND_VAR });; or can be accessed directly from the AppConfig pack
age:

use AppConfig;

$state->define('foo', { EXPAND => AppConfig::EX

PAND_VAR });; The following values for EXPAND may be specified.
Multiple values should be combined with vertical bars
, '|', e.g. "EXPAND_UID | EXPAND_VAR").; EXPAND_NONE
Indicates that no variable expansion should be
attempted.; EXPAND_VAR
Indicates that variables embedded as $var or
$(var) should be expanded to the values of the
relevant AppConfig::State variables.; EXPAND_UID
Indicates that '~' or '~uid' patterns in the
string should be expanded to the current users
($<), or specified user's home directory.; EXPAND_ENV
Inidicates that variables embedded as ${var}
should be expanded to the value of the relevant
environment variable.; EXPAND_ALL
Equivalent to "EXPAND_VARS | EXPAND_UIDS
EXPAND_ENVS").; EXPAND_WARN
Indicates that embedded variables that are not
defined should raise a warning. If PEDANTIC is
set, this will cause the read() method to return 0 immediately.
VALIDATE: Each variable may have a sub-routine or regular
expression defined which is used to validate the
intended value for a variable before it is set.; If VALIDATE is defined as a regular expression, it is
applied to the value and deemed valid if the pattern
matches. In this case, the variable is then set to
the new value. A warning message is generated if the
pattern match fails.; VALIDATE may also be defined as a reference to a subroutine which takes as its arguments the name of the
variable and its intended value. The sub-routine
should return 1 or 0 to indicate that the value is
valid or invalid, respectively. An invalid value will
cause a warning error message to be generated.; If the GLOBAL VALIDATE variable is set (see GLOBAL in
DESCRIPTION above) then this value will be used as the
default VALIDATE for each variable unless otherwise
specified.

$state->define("age", {
VALIDATE => '+',

});; $state->define("pin", {
VALIDATE => check_pin,; });
ACTION: The ACTION option allows a sub-routine to be bound to
a variable as a callback that is executed whenever the
variable is set. The ACTION is passed a reference to
the AppConfig::State object, the name of the variable
and the value of the variable.; The ACTION routine may be used, for example, to postprocess variable data, update the value of some other
dependant variable, generate a warning message, etc.; Example:

$state->define("foo", { ACTION => my_notify });

sub my_notify {
my $state = shift;
my $var = shift;
my $val = shift;

print "$variable set to $value";

}

$state->foo(42); # prints "foo set to 42"; Be aware that calling "$state->set()" to update the
same variable from within the ACTION function will
cause a recursive loop as the ACTION function is
repeatedly called.
�
DEFINING VARIABLES USING THE COMPACT FORMAT
Variables may be defined in a compact format which allows any ALIAS and ARGS values to be specified as part of the variable name. This is designed to mimic the behaviour of Johan Vromans' Getopt::Long module.
Aliases for a variable should be specified after the vari able name, separated by vertical bars, '|'. Any ARGS parameter should be appended after the variable name(s) and/or aliases.
The following examples are equivalent:: $state->define("foo", {
ALIAS => [ 'bar', 'baz' ],
ARGS => '=i',; });
$state->define("foo|bar|baz=i");
READING AND MODIFYING VARIABLE VALUES
AppConfig::State defines two methods to manipulate vari able values:: set($variable, $value);
get($variable);
Both functions take the variable name as the first parame ter and "set()" takes an additional parameter which is the new value for the variable. "set()" returns 1 or 0 to indicate successful or unsuccessful update of the variable value. If there is an ACTION routine associated with the named variable, the value returned will be passed back from "set()". The "get()" function returns the current value of the variable.
Once defined, variables may be accessed directly as object methods where the method name is the same as the variable name. i.e.: $state->set("verbose", 1);
is equivalent to: $state->verbose(1);
Without parameters, the current value of the variable is returned. If a parameter is specified, the variable is set to that value and the result of the set() operation is returned.: $state->age(29); # sets 'age' to 29, returns 1; (ok)
INTERNAL METHODS
The interal (private) methods of the AppConfig::State class are listed below.
They aren't intended for regular use and potential users should consider the fact that nothing about the internal implementation is guaranteed to remain the same. Having said that, the AppConfig::State class is intended to coexist and work with a number of other modules and these are considered "friend" classes. These methods are pro vided, in part, as services to them. With this acknowl edged co-operation in mind, it is safe to assume some sta bility in this core interface.
The _varname() method can be used to determine the real name of a variable from an alias:: $varname->_varname($alias);
Note that all methods that take a variable name, including
those listed below, can accept an alias and automatically
resolve it to the correct variable name. There is no need
to call _varname() explicitly to do alias expansion. The _varname() method will fold all variables names to lower case unless CASE sensititvity is set.
The _exists() method can be used to check if a variable has been defined:: $state->_exists($varname);
The _default() method can be used to reset a variable to its default value:: $state->_default($varname);
The _expand() method can be used to determine the EXPAND value for a variable:: print "$varname EXPAND: ", $state->_expand($varname),; "0;
The _argcount() method returns the value of the ARGCOUNT attribute for a variable:: print "$varname ARGCOUNT: ", $state->_argcount($var; name), "0;
The _validate() method can be used to determine if a new value for a variable meets any validation criteria speci
fied for it. The variable name and intended value should
be passed in. The methods returns a true/false value
depending on whether or not the validation succeeded:: print "OK0 if $state->_validate($varname, $value);
The _pedantic() method can be called to determine the cur rent value of the PEDANTIC option.: print "pedantic mode is ", $state->_pedantic() ? "on"; ; "off", "0;
The _debug() method can be used to turn debugging on or off (pass 1 or 0 as a parameter). It can also be used to
check the debug state, returning the current internal
value of $AppConfig::State::DEBUG. If a new debug value
is provided, the debug state is updated and the previous
state is returned.: $state->_debug(1); # debug on, returns; previous value
The _dump_var($varname) and _dump() methods may also be
called for debugging purposes.: $state->_dump_var($varname); # show variable state
$state->_dump(); # show internal state; and all vars

AUTHOR

Andy Wardley, "<abw@cre.canon.co.uk>"

Web Technology Group, Canon Research Centre Europe Ltd.

REVISION

$Revision: 1.52 $

COPYRIGHT

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

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