ajf / newtype
A handy function for creating opaque types
Requires
- php: >=7.0.0
Requires (Dev)
- phpunit/phpunit: ^5.0
This package is not auto-updated.
Last update: 2024-11-09 18:59:25 UTC
README
newType()
is a handy function for creating opaque types, that is, a type that merely wraps another type. It takes two parameters: the name of your new wrapper type, and the name of the type you want to wrap. You get a class with a constructor taking a value of the wrapped type, and an ->unbox()
method to get out the value of the wrapped type.
Require it with composer require ajf/newtype
to use it. It's PHP 7-only, since PHP 7 is the first version of PHP with scalar type declarations. It would be possible to backport this, though.
An example of where you might use this:
<?php namespace JaneBlogges\WonderfulApp; use function ajf\newType\newType; // Makes the new opaque type! newType(FilePath::class, 'string'); function moveFile(FilePath $sourcePath, FilePath $destinationPath): bool { return rename($sourcePath->unbox(), $destinationPath->unbox()); } moveFile(new FilePath('foo'), new FilePath('bar'));
Use it for that extra bit of type safety!
If you're after a mere alias that doesn't require explicit conversion to and from, check out PHP's built-in class\_alias
function - though beware that only works with classes and not primitive types.
The name comes from Haskell's newtype
declaration, which does the same thing:
newtype FilePath = FilePath String
It's similar to Hack's newtype
declaration as well, although that works a little differently.