4 ms·

It would be nice if languages provided mechanisms to support composition without the bureaucracy. Why should we write a ton of boilerplate just to forward a me

It would be nice if languages provided mechanisms to support composition without the bureaucracy. Why should we write a ton of boilerplate just to forward a message to a contained object? Why can't we just have: type MyType { member containedObject SomeOtherType forwardTo(containedObject) MethodA, MethodB as SomeOtherName, MethodC method SomeNewMethod() {some implementation} } Then the compiler can optimize the path to call the delegated object directly rather than through a secondary call via this object, since it knows what our intent is.

perlgeek 8y ago
Perl 6 does, with a "handles" trait: class MyType { has SomeOtherType $.containedObject handles ('MethodA', MethodB => 'SomeOtherName', 'MethodC'); } Very useful when you need it. https://docs.perl6.org/language/typesystem#trait_handles https://docs.perl6.org/language/typesystem#trait_handles
- fanf2 8y ago
  Similar in perl5 with Moose or Moo package MyClass; use Moo; has member => ( is => ‘rw’, handles => [qw[ methodA methodB ]] );
gridlockd 8y ago
Some languages do specify Mixins, but even multiple inheritance is better than the oversold "composition pattern". The composition pattern is just one of the many ways Java programmers figured out to write more code that does essentially nothing. That's why Java programmers will be in demand forever, whereas more productive programmers will optimize themselves out of a job.
zmmmmm 8y ago
That's exactly what Groovy provides with the @Delegate annotation [1] [1] http://docs.groovy-lang.org/2.4.9/html/gapi/groovy/lang/Delegate.html http://docs.groovy-lang.org/2.4.9/html/gapi/groovy/lang/Dele...
unicornmama 8y ago
Golang supports exactly this use case.
cinnamonheart 8y ago
Dotty (Scala 3) recently added support for forwarding to a contained object via an 'export' keyword. class A { def foo(): String = ... def bar(): String = ... def baz(): String = ... } class B { private val a: A = new A() def foo(): String = ... // Export a's methods as b's, except for foo, and rename baz as qux export a.{foo => _, baz => qux, _} } val b = new B() b.foo() // b's implementation b.bar() // a's b.qux() // a's baz
marcosdumay 8y ago
They do. It's called inheritance.
chucksmash 8y ago
Kotlin has this[0]. Rust is talking about adding it as well[1]. I guess Haskell does too[2]. [0]: https://kotlinlang.org/docs/reference/delegation.html https://kotlinlang.org/docs/reference/delegation.html [1]: https://github.com/rust-lang/rfcs/pull/2393 https://github.com/rust-lang/rfcs/pull/2393 [2]: https://downloads.haskell.org/~ghc/5.04/docs/html/users_guide/newtype-deriving.html https://downloads.haskell.org/~ghc/5.04/docs/html/users_guid...

perlgeek 8y ago

Perl 6 does, with a "handles" trait: class MyType { has SomeOtherType $.containedObject handles ('MethodA', MethodB => 'SomeOtherName', 'MethodC'); } Very useful when you need it. https://docs.perl6.org/language/typesystem#trait_handles https://docs.perl6.org/language/typesystem#trait_handles

fanf2 8y ago
Similar in perl5 with Moose or Moo package MyClass; use Moo; has member => ( is => ‘rw’, handles => [qw[ methodA methodB ]] );

gridlockd 8y ago

Some languages do specify Mixins, but even multiple inheritance is better than the oversold "composition pattern". The composition pattern is just one of the many ways Java programmers figured out to write more code that does essentially nothing. That's why Java programmers will be in demand forever, whereas more productive programmers will optimize themselves out of a job.

zmmmmm 8y ago

That's exactly what Groovy provides with the @Delegate annotation [1] [1] http://docs.groovy-lang.org/2.4.9/html/gapi/groovy/lang/Delegate.html http://docs.groovy-lang.org/2.4.9/html/gapi/groovy/lang/Dele...

unicornmama 8y ago

Golang supports exactly this use case.

cinnamonheart 8y ago

Dotty (Scala 3) recently added support for forwarding to a contained object via an 'export' keyword. class A { def foo(): String = ... def bar(): String = ... def baz(): String = ... } class B { private val a: A = new A() def foo(): String = ... // Export a's methods as b's, except for foo, and rename baz as qux export a.{foo => _, baz => qux, _} } val b = new B() b.foo() // b's implementation b.bar() // a's b.qux() // a's baz

marcosdumay 8y ago

They do. It's called inheritance.

chucksmash 8y ago

Kotlin has this[0]. Rust is talking about adding it as well[1]. I guess Haskell does too[2]. [0]: https://kotlinlang.org/docs/reference/delegation.html https://kotlinlang.org/docs/reference/delegation.html [1]: https://github.com/rust-lang/rfcs/pull/2393 https://github.com/rust-lang/rfcs/pull/2393 [2]: https://downloads.haskell.org/~ghc/5.04/docs/html/users_guide/newtype-deriving.html https://downloads.haskell.org/~ghc/5.04/docs/html/users_guid...