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 callbacks 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()
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 reference 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 values. You can initialise the object by passing
a reference to a hash array containing configuration options:
$state = AppConfig::State->new( {
CASE => 1,
ERROR => \&my_error,
} );
The
new() constructor of the AppConfig module automatically passes all
parameters to the AppConfig::State
new() constructor. Thus, any global
configuration values and variable definitions for AppConfig::State are also
applicable to AppConfig.
The following configuration options may be specified.
- CASE
- Determines if the variable names are treated case sensitively. Any
non-zero value makes case significant when naming variables. By default,
CASE is set to 0 and thus "Variable", "VARIABLE" and
"VaRiAbLe" are all treated as "variable".
- CREATE
- By default, CREATE is turned off meaning that all variables accessed via
set() (which includes access via shortcut such as
"$state->variable($value)" which delegates to set())
must previously have been defined via define(). When CREATE is set
to 1, calling set($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 created. This can be used to specify configuration file blocks
in which variables should be created, for example:
$state = AppConfig::State->new( {
CREATE => '^define_',
} );
In a config file:
[define]
name = fred # define_name gets created automatically
[other]
name = john # other_name doesn't - warning raised
Note that a regex pattern specified in CREATE is applied to the real
variable name rather than any alias by which the variables may be
accessed.
- PEDANTIC
- The PEDANTIC option determines what action the configuration file
(AppConfig::File) or argument parser (AppConfig::Args) should take on
encountering a warning condition (typically caused when trying to set an
undeclared variable). If PEDANTIC is set to any true value, the parsing
methods will immediately return a value of 0 on encountering such a
condition. If PEDANTIC is not set, the method will continue to parse the
remainder of the current file(s) or arguments, returning 0 when complete.
If no warnings or errors are encountered, the method returns 1.
In the case of a system error (e.g. unable to open a file), the method
returns undef immediately, regardless of the PEDANTIC option.
- ERROR
- Specifies a user-defined error handling routine. When the handler is
called, a format string is passed as the first parameter, followed by any
additional values, as per printf(3C).
- DEBUG
- Turns debugging on or off when set to 1 or 0 accordingly. Debugging may
also be activated by calling _debug() as an object method
("$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 $AppConfig::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 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 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 alternatives or as
a string of names separated by vertical 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 arguments are
expected for variables (ARGCOUNT_NONE).
The ARGCOUNT_* constants can be imported from the AppConfig module:
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 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 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 $(var) should be expanded to
the values of the relevant AppConfig::State variables.
- EXPAND_UID
- Indicates that '~' or '~uid' patterns in the string should be expanded to
the current users ($<), 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 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.
-
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
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 co-exist
and work with a number of other modules and these are considered
"friend" classes. These methods are provided, in part, as services
to them. With this acknowledged co-operation in mind, it is safe to assume
some stability 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), "\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 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@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