From: markstos Date: Sat, 11 Apr 2009 11:50:08 +0000 (-0400) Subject: Improve documentation for type constraints. X-Git-Tag: 0.21~5^2~1 X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=5893ee369af9cdefdea2bafa641d4b4470fd91c1;p=gitmo%2FMouse.git Improve documentation for type constraints. --- diff --git a/Changes b/Changes index 80b46a6..2e25ef4 100644 --- a/Changes +++ b/Changes @@ -1,7 +1,7 @@ Revision history for Mouse 0.21 - + * Added documentation about type constraints (Mark Stosberg) 0.20 Thu Apr 9 20:22:33 2009 * Squirrel is now deprecated. Use Any::Moose instead (Sartak) diff --git a/lib/Mouse.pm b/lib/Mouse.pm index 8e0566d..ef101e1 100644 --- a/lib/Mouse.pm +++ b/lib/Mouse.pm @@ -305,10 +305,16 @@ the attribute. =item isa => TypeConstraint -Provides basic type checking in the constructor and accessor. Basic types such -as C, C, C are supported. Any unknown type is taken to -be a class check (e.g. isa => 'DateTime' would accept only L -objects). +Provides type checking in the constructor and accessor. The following types are +supported. Any unknown type is taken to be a class check (e.g. isa => +'DateTime' would accept only L objects). + + Any Item Bool Undef Defined Value Num Int Str ClassName + Ref ScalarRef ArrayRef HashRef CodeRef RegexpRef GlobRef + FileHandle Object + +For more documentation on type constraints, see L. + =item required => 0|1 diff --git a/lib/Mouse/Util/TypeConstraints.pm b/lib/Mouse/Util/TypeConstraints.pm index 650bfca..cf03de9 100644 --- a/lib/Mouse/Util/TypeConstraints.pm +++ b/lib/Mouse/Util/TypeConstraints.pm @@ -342,7 +342,165 @@ __END__ =head1 NAME -Mouse::Util::TypeConstraints - simple type constraints +Mouse::Util::TypeConstraints - Type constraint system for Mouse + +=head2 SYNOPSIS + + use Mouse::Util::TypeConstraints; + + subtype 'Natural' + => as 'Int' + => where { $_ > 0 }; + + subtype 'NaturalLessThanTen' + => as 'Natural' + => where { $_ < 10 } + => message { "This number ($_) is not less than ten!" }; + + coerce 'Num' + => from 'Str' + => via { 0+$_ }; + + enum 'RGBColors' => qw(red green blue); + + no Mouse::Util::TypeConstraints; + +=head1 DESCRIPTION + +This module provides Mouse with the ability to create custom type +constraints to be used in attribute definition. + +=head2 Important Caveat + +This is B a type system for Perl 5. These are type constraints, +and they are not used by Mouse unless you tell it to. No type +inference is performed, expressions are not typed, etc. etc. etc. + +A type constraint is at heart a small "check if a value is valid" +function. A constraint can be associated with an attribute. This +simplifies parameter validation, and makes your code clearer to read, +because you can refer to constraints by name. + +=head2 Slightly Less Important Caveat + +It is B a good idea to quote your type names. + +This prevents Perl from trying to execute the call as an indirect +object call. This can be an issue when you have a subtype with the +same name as a valid class. + +For instance: + + subtype DateTime => as Object => where { $_->isa('DateTime') }; + +will I, while this: + + use DateTime; + subtype DateTime => as Object => where { $_->isa('DateTime') }; + +will fail silently and cause many headaches. The simple way to solve +this, as well as future proof your subtypes from classes which have +yet to have been created, is to quote the type name: + + use DateTime; + subtype 'DateTime' => as 'Object' => where { $_->isa('DateTime') }; + +=head2 Default Type Constraints + +This module also provides a simple hierarchy for Perl 5 types, here is +that hierarchy represented visually. + + Any + Item + Bool + Maybe[`a] + Undef + Defined + Value + Num + Int + Str + ClassName + RoleName + Ref + ScalarRef + ArrayRef[`a] + HashRef[`a] + CodeRef + RegexpRef + GlobRef + FileHandle + Object + Role + +B Any type followed by a type parameter C<[`a]> can be +parameterized, this means you can say: + + ArrayRef[Int] # an array of integers + HashRef[CodeRef] # a hash of str to CODE ref mappings + Maybe[Str] # value may be a string, may be undefined + +If Mouse finds a name in brackets that it does not recognize as an +existing type, it assumes that this is a class name, for example +C. + +B Unless you parameterize a type, then it is invalid to include +the square brackets. I.e. C will be treated as a new type +name, I as a parameterization of C. + +B The C type constraint for the most part works +correctly now, but edge cases may still exist, please use it +sparingly. + +B The C type constraint does a complex package +existence check. This means that your class B be loaded for this +type constraint to pass. + +B The C constraint checks a string is a I which is a role, like C<'MyApp::Role::Comparable'>. The C +constraint checks that an I the named role. + +=head2 Type Constraint Naming + +Type name declared via this module can only contain alphanumeric +characters, colons (:), and periods (.). + +Since the types created by this module are global, it is suggested +that you namespace your types just as you would namespace your +modules. So instead of creating a I type for your +B module, you would call the type +I instead. + +=head2 Use with Other Constraint Modules + +This module can play nicely with other constraint modules with some +slight tweaking. The C clause in types is expected to be a +C reference which checks it's first argument and returns a +boolean. Since most constraint modules work in a similar way, it +should be simple to adapt them to work with Mouse. + +For instance, this is how you could use it with +L to declare a completely new type. + + type 'HashOfArrayOfObjects', + { + where => IsHashRef( + -keys => HasLength, + -values => IsArrayRef(IsObject) + ) + }; + +Here is an example of using L and it's non-test +related C function. + + type 'ArrayOfHashOfBarsAndRandomNumbers' + => where { + eq_deeply($_, + array_each(subhashof({ + bar => isa('Bar'), + random_number => ignore() + }))) + }; =head1 METHODS @@ -366,6 +524,10 @@ Returns the simple type constraints that Mouse understands. =back +=head1 THANKS + +Much of this documentation was taken from L + =cut