---
name: "Declare::Constraints::Simple::Library::Base"
section: "3pm"
platform: "linux"
package: "libdeclare-constraints-simple-perl"
version: "0.03-1.1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Declare::Constraints::Simple::Library::Base"
---

# Declare::Constraints::Simple::Library::Base(3pm)

Library Base Class

## NAME

Declare::Constraints::Simple::Library::Base - Library Base Class

## SYNOPSIS

```
  package My::Constraint::Library;
  use warnings;
  use strict;
  # this installs the base class and helper functions
  use Declare::Constraints::Simple-Library;
  # we can also automagically provide other libraries
  # to the importer
  use base 'Declare::Constraints::Simple::Library::Numericals';
  # with this we define a constraint to check a value
  # against a serial number regular expression
  constraint 'SomeSerial',
    sub {
      return sub {
        return _true if $_[0] =~ /\d{3}-\d{3}-\d{4}/;
        return _false('Not in SomeSerial format');
      };
    };

  1;
```

## DESCRIPTION

This base class contains the common library functionalities. This  includes helper functions and install mechanisms.

## METHODS

### install\_into($target)

Installs the base classes and helper functions into the `$target` namespace. The `%CONSTRAINT_GENERATORS` package variable of that class will be used as storage for it's constraints.

### fetch\_constraint\_declarations()

Class method. Returns all constraints registered to the class.

### fetch\_constraint\_generator($name)

Class method. Returns the constraint generator code reference registered under `$name`. The call will raise a `"croak"` if the generator could not be found.

### prepare\_generator($constraint\_name, $generator)

Class method. This wraps the `$generator` in a closure that provides stack and failure-collapsing decisions.

### add\_constraint\_generator($name, $code)

Class method. The actual registration method, used by `"constraint"`.

## HELPER FUNCTIONS

Note that some of the helper functions are prefixed with `"_"`. Although this means they are internal functions, it is ok to call them, as they have a fixed API. They are not distribution internal, but library  internal, and only intended to be used from inside constraints.

### constraint($name, $code)

```
  constraint 'Foo', sub { ... };
```

This registers a new constraint in the calling library. Note that constraints **have to** return result objects. To do this, you can use the helper functions "\_result($bool, `$msg`", **\_true()** and \_false($msg).

### \_result($bool, $msg)

Returns a new result object. It's validity flag will depend on the `$bool` argument. The `$msg` argument is the error message to use on failure.

### \_false($msg)

Returns a non-valid result object, with it's message set to `$msg`.

### \_true()

Returns a valid result object.

### \_info($info)

Sets the current failure info to use in the stack info part.

### \_apply\_checks($value, \\@constraints, \[$info\])

This applies all constraints in the `"\@constraints"` array reference to the passed `$value`. You can optionally specify an `$info` string to be used in the stack of the newly created non-valid results.

### \_listify($value)

Puts `$value` into an array reference and returns it, if it isn't  already one.

### \_with\_message($msg, $closure, @args)

This is the internal version of the general `"Message"` constraint. It  sets the current overridden message to `$msg` and executes the `$closure` with `@args` as arguments.

### \_with\_scope($scope\_name, $constraint, @args)

Applies the `$constraint` to `@args` in a newly created scope named by `$scope_name`.

### \_set\_result($scope, $name, $result)

Stores the given `$result` unter the name `$name` in `$scope`.

### \_get\_result($scope, $name)

Returns the result named `$name` from `$scope`.

### \_has\_result($scope, $name)

Returns true only if such a result was registered already.

## SEE ALSO

Declare::Constraints::Simple, Declare::Constraints::Simple::Library

## AUTHOR

Robert 'phaylon' Sedlacek `"<phaylon@dunkelheit.at>"`

## LICENSE AND COPYRIGHT

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