1
0
Fork 0

Trait can now implement interfaces

Note the incomplete test case: the next commit will introduce the ability
for mixins to override methods that may have already been defined.
perfodd
Mike Gerwitz 2014-02-28 23:55:24 -05:00
parent c8023cb382
commit 14bd552361
3 changed files with 279 additions and 5 deletions

View File

@ -74,6 +74,9 @@ function createNamedTrait( name, dfn )
Trait.extend = function( dfn ) Trait.extend = function( dfn )
{ {
// we may have been passed some additional metadata
var meta = this.__$$meta || {};
// store any provided name, since we'll be clobbering it (the definition // store any provided name, since we'll be clobbering it (the definition
// object will be used to define the hidden abstract class) // object will be used to define the hidden abstract class)
var name = dfn.__name || '(Trait)'; var name = dfn.__name || '(Trait)';
@ -91,8 +94,15 @@ Trait.extend = function( dfn )
throw Error( "Cannot instantiate trait" ); throw Error( "Cannot instantiate trait" );
}; };
// implement interfaces if indicated
var base = AbstractClass;
if ( meta.ifaces )
{
base = base.implement.apply( null, meta.ifaces );
}
// and here we can see that traits are quite literally abstract classes // and here we can see that traits are quite literally abstract classes
var tclass = AbstractClass( dfn ); var tclass = base.extend( dfn );
TraitType.__trait = true; TraitType.__trait = true;
TraitType.__acls = tclass; TraitType.__acls = tclass;
@ -114,10 +124,33 @@ Trait.extend = function( dfn )
mixin( TraitType, dfn, tc ); mixin( TraitType, dfn, tc );
}; };
// mixes in implemented types
TraitType.__mixinImpl = function( dest_meta )
{
mixinImpl( tclass, dest_meta );
};
return TraitType; return TraitType;
}; };
Trait.implement = function()
{
var ifaces = arguments;
return {
extend: function()
{
// pass our interface metadata as the invocation context
return Trait.extend.apply(
{ __$$meta: { ifaces: ifaces } },
arguments
);
},
};
};
Trait.isTrait = function( trait ) Trait.isTrait = function( trait )
{ {
return !!( trait || {} ).__trait; return !!( trait || {} ).__trait;
@ -260,16 +293,71 @@ function createVirtProxy( acls, dfn )
function mixin( trait, dfn, tc ) function mixin( trait, dfn, tc )
{ {
// the abstract class hidden within the trait // the abstract class hidden within the trait
var acls = trait.__acls, var acls = trait.__acls;
methods = acls.___$$methods$$;
// retrieve the private member name that will contain this trait object // retrieve the private member name that will contain this trait object
var iname = addTraitInst( trait, dfn, tc ); var iname = addTraitInst( trait, dfn, tc );
// recursively mix in trait's underlying abstract class (ensuring that
// anything that the trait inherits from is also properly mixed in)
mixinCls( acls, dfn, iname );
return dfn;
}
/**
* Recursively mix in class methods
*
* If CLS extends another class, its methods will be recursively processed
* to ensure that the entire prototype chain is properly proxied.
*
* For an explanation of the iname parameter, see the mixin function.
*
* @param {Class} cls class to mix in
* @param {Object} dfn definition object to merge into
* @param {string} iname trait object private member instance name
*
* @return {undefined}
*/
function mixinCls( cls, dfn, iname )
{
var methods = cls.___$$methods$$;
mixMethods( methods['public'], dfn, 'public', iname ); mixMethods( methods['public'], dfn, 'public', iname );
mixMethods( methods['protected'], dfn, 'protected', iname ); mixMethods( methods['protected'], dfn, 'protected', iname );
return dfn; // if this class inherits from another class that is *not* the base
// class, recursively process its methods; otherwise, we will have
// incompletely proxied the prototype chain
var parent = methods['public'].___$$parent$$;
if ( parent && ( parent.constructor !== ClassBuilder.ClassBase ) )
{
mixinCls( parent.constructor, dfn, iname );
}
}
/**
* Mix implemented types into destination object
*
* The provided destination object will ideally be the `implemented' array
* of the destination class's meta object.
*
* @param {Class} cls source class
* @param {Object} dest_meta destination object to copy into
*
* @return {undefined}
*/
function mixinImpl( cls, dest_meta )
{
var impl = ClassBuilder.getMeta( cls ).implemented || [],
i = impl.length;
while ( i-- )
{
// TODO: this could potentially result in duplicates
dest_meta.push( impl[ i ] );
}
} }

View File

@ -431,9 +431,11 @@ function createMixedClass( base, traits )
// add each trait to the list of implemented types so that the // add each trait to the list of implemented types so that the
// class is considered to be of type T in traits // class is considered to be of type T in traits
var impl = meta.implemented;
for ( var i = 0, n = traits.length; i < n; i++ ) for ( var i = 0, n = traits.length; i < n; i++ )
{ {
meta.implemented.push( traits[ i ] ); impl.push( traits[ i ] );
traits[ i ].__mixinImpl( impl );
} }
return C; return C;

View File

@ -0,0 +1,184 @@
/**
* Tests overriding virtual class methods using mixins
*
* Copyright (C) 2014 Mike Gerwitz
*
* This file is part of GNU ease.js.
*
* ease.js is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* These tests vary from those in VirtualTest in that, rather than a class
* overriding a virtual method defined within a trait, a trait is overriding
* a method in the class that it is mixed into. In particular, since
* overrides require that the super method actually exist, this means that a
* trait must implement or extend a common interface.
*
* It is this very important (and powerful) system that allows traits to be
* used as stackable modifications, similar to how one would use the
* decorator pattern (but more tightly coupled).
*/
require( 'common' ).testCase(
{
caseSetUp: function()
{
this.Sut = this.require( 'Trait' );
this.Class = this.require( 'class' );
this.AbstractClass = this.require( 'class_abstract' );
this.Interface = this.require( 'interface' );
},
/**
* A trait may implement an interface I for a couple of reasons: to have
* the class mixed into be considered to of type I and to override
* methods. But, regardless of the reason, let's start with the
* fundamentals.
*/
'Traits may implement an interface': function()
{
var _self = this;
// simply make sure that the API is supported; nothing more.
this.assertDoesNotThrow( function()
{
_self.Sut.implement( _self.Interface( {} ) ).extend( {} );
} );
},
/**
* We would expect that the default behavior of implementing an
* interface I into a trait would create a trait with all abstract
* methods defined by I.
*/
'Traits implementing interfaces define abstract methods': function()
{
var I = this.Interface( { foo: [], bar: [] } ),
T = this.Sut.implement( I ).extend( {} );
var Class = this.Class,
AbstractClass = this.AbstractClass;
// T should contain both foo and bar as abstract methods, which we
// will test indirectly in the assertions below
// should fail because of abstract foo and bar
this.assertThrows( function()
{
Class.use( T ).extend( {} );
} );
// should succeed, since we can have abstract methods within an
// abstract class
this.assertDoesNotThrow( function()
{
AbstractClass.use( T ).extend( {} );
} );
// one remaining abstract method
this.assertDoesNotThrow( function()
{
AbstractClass.use( T ).extend( { foo: function() {} } );
} );
// both concrete
this.assertDoesNotThrow( function()
{
Class.use( T ).extend(
{
foo: function() {},
bar: function() {},
} );
} );
},
/**
* Just as classes implementing interfaces may choose to immediately
* provide concrete definitions for the methods declared in the
* interface (instead of becoming an abstract class), so too may traits.
*/
'Traits may provide concrete methods for interfaces': function()
{
var called = false;
var I = this.Interface( { foo: [] } ),
T = this.Sut.implement( I ).extend(
{
foo: function()
{
called = true;
},
} );
var Class = this.Class;
this.assertDoesNotThrow( function()
{
// should invoke concrete foo; class definition should not fail,
// because foo is no longer abstract
Class.use( T )().foo();
} );
this.assertOk( called );
},
/**
* Instances of class C mixing in some trait T implementing I will be
* considered to be of type I, since any method of I would either be
* defined within T, or would be implicitly abstract in T, requiring its
* definition within C; otherwise, C would have to be declared astract.
*/
'Instance of class mixing in trait implementing I is of type I':
function()
{
var I = this.Interface( {} ),
T = this.Sut.implement( I ).extend( {} );
this.assertOk(
this.Class.isA( I, this.Class.use( T )() )
);
},
/**
* The API for multiple interfaces should be the same for traits as it
* is for classes.
*/
'Trait can implement multiple interfaces': function()
{
var Ia = this.Interface( {} ),
Ib = this.Interface( {} ),
T = this.Sut.implement( Ia, Ib ).extend( {} ),
o = this.Class.use( T ).extend( {} )();
this.assertOk( this.Class.isA( Ia, o ) );
this.assertOk( this.Class.isA( Ib, o ) );
},
/**
* This is a concept borrowed from Scala: consider class C and trait T,
* both implementing interface I which declares method M. T should be
* able to override C.M so long as it is concrete, but to do so, we need
* some way of telling ease.js that we are overriding at time of mixin;
* otherwise, override does not make sense, because I.M is clearly
* abstract and there is nothing to override.
*/
'Trait can override virtual concrete interface methods at mixin':
function()
{
},
} );