AppConfig::State
AppConfig::State(3) User Contributed Perl Documentation AppConfig::State(3)
NAME
AppConfig::State - application configuration state
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 configuration
variables for perl programs. It maintains the state of any number of
variables, handling default values, aliasing, validation, update call-
backs and option arguments 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 following line
should appear in your Perl script:
use AppConfig::State;
The AppConfig::State module is loaded automatically by the new() con-
structor 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 reference to a new AppConfig::State object.
my $state = AppConfig::State->new();
This will create a reference to a new AppConfig::State with all con-
figuration options set to their default values. You can initialise
the object by passing a reference to a hash array containing configu-
ration options:
$state = AppConfig::State->new( {
CASE => 1,
ERROR => \&my_error,
} );
The new() constructor of the AppConfig module automatically passes all
parameters to the AppConfig::State new() constructor. Thus, any
global configuration values and variable definitions for AppCon-
fig::State are also applicable to AppConfig.
The following configuration options may be specified.
CASE
Determines if the variable names are treated case sensitively.
Any non-zero value makes case significant when naming variables.
By default, CASE is set to 0 and thus "Variable", "VARIABLE" and
"VaRiAbLe" are all treated as "variable".
CREATE
By default, CREATE is turned off meaning that all variables
accessed via set() (which includes access via shortcut such as
"$state->variable($value)" which delegates to set()) must previ-
ously have been defined via define(). When CREATE is set to 1,
calling set($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 created. This can be used to specify con-
figuration file blocks in which variables should be created, for
example:
$state = AppConfig::State->new( {
CREATE => ’^define_’,
} );
In a config file:
[define]
name = fred # define_name gets created automatically
[other]
name = john # other_name doesn’t - warning raised
Note that a regex pattern specified in CREATE is applied to the
real variable name rather than any alias by which the variables
may be accessed.
PEDANTIC
The PEDANTIC option determines what action the configuration file
(AppConfig::File) or argument parser (AppConfig::Args) should take
on encountering a warning condition (typically caused when trying
to set an undeclared variable). If PEDANTIC is set to any true
value, the parsing methods will immediately return a value of 0 on
encountering such a condition. If PEDANTIC is not set, the method
will continue to parse the remainder of the current file(s) or
arguments, returning 0 when complete.
If no warnings or errors are encountered, the method returns 1.
In the case of a system error (e.g. unable to open a file), the
method returns undef immediately, regardless of the PEDANTIC
option.
ERROR
Specifies a user-defined error handling routine. When the handler
is called, a format string is passed as the first parameter, fol-
lowed by any additional values, as per printf(3C).
DEBUG
Turns debugging on or off when set to 1 or 0 accordingly. Debug-
ging may also be activated by calling _debug() as an object method
("$state->_debug(1)") or as a package function (AppCon-
fig::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 previ-
ous 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 configura-
tion information for the variable:
$state->define("foo", {
DEFAULT => 99,
ALIAS => ’metavar1’,
});
Any variable-wide GLOBAL values passed to the new() constructor in the
configuration hash will also be applied. Values explicitly specified
in a variable’s define() configuration 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 speci-
fied for this variable. A single alias should be specified as a
string. Multiple aliases can be specified as a reference to an
array of alternatives or as a string of names separated by verti-
cal bars, ’│’. e.g.:
# either
$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 argu-
ments are expected for variables (ARGCOUNT_NONE).
The ARGCOUNT_* constants can be imported from the AppConfig mod-
ule:
use AppConfig ’:argcount’;
$state->define(’foo’, { ARGCOUNT => ARGCOUNT_ONE });
or can be accessed directly from the AppConfig package:
use AppConfig;
$state->define(’foo’, { ARGCOUNT => AppConfig::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 confirguration file or in the com-
mand 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 argument 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 arguments 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 values 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 configuration 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 AppConfig module:
use AppConfig ’:expand’;
$state->define(’foo’, { EXPAND => EXPAND_VAR });
or can be accessed directly from the AppConfig package:
use AppConfig;
$state->define(’foo’, { EXPAND => AppConfig::EXPAND_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 $(var) should be
expanded to the values of the relevant AppConfig::State vari-
ables.
EXPAND_UID
Indicates that ’~’ or ’~uid’ patterns in the string should be
expanded to the current users ($<), or specified user’s home
directory. In the first case, "~" is expanded to the value of
the "HOME" environment variable. In the second case, the
"getpwnam()" method is used if it is available on your system
(which it isn’t on Win32).
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 sub-routine 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 => ’\d+’,
});
$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 post-process vari-
able data, update the value of some other dependant variable, gen-
erate 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 variable 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’,
});
$state->define("foo│bar│baz=i");
READING AND MODIFYING VARIABLE VALUES
AppConfig::State defines two methods to manipulate variable values:
set($variable, $value);
get($variable);
Both functions take the variable name as the first parameter and
"set()" takes an additional parameter which is the new value for the
variable. "set()" returns 1 or 0 to indicate successful or unsuccess-
ful update of the variable value. If there is an ACTION routine asso-
ciated 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 con-
sider the fact that nothing about the internal implementation is guar-
anteed to remain the same. Having said that, the AppConfig::State
class is intended to co-exist 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 acknowledged co-opera-
tion in mind, it is safe to assume some stability in this core inter-
face.
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), "\n";
The _argcount() method returns the value of the ARGCOUNT attribute for
a variable:
print "$varname ARGCOUNT: ", $state->_argcount($varname), "\n";
The _validate() method can be used to determine if a new value for a
variable meets any validation criteria specified 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 "OK\n" if $state->_validate($varname, $value);
The _pedantic() method can be called to determine the current value of
the PEDANTIC option.
print "pedantic mode is ", $state->_pedantic() ? "on" ; "off", "\n";
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 pre-
vious 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@wardley.org>
COPYRIGHT
Copyright (C) 1997-2007 Andy Wardley. All Rights Reserved.
Copyright (C) 1997,1998 Canon Research Centre Europe Ltd.
This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
SEE ALSO
AppConfig, AppConfig::File, AppConfig::Args, AppConfig::Getopt
perl v5.8.8 2007-05-30 AppConfig::State(3)
