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
parent
c8023cb382
commit
14bd552361
96
lib/Trait.js
96
lib/Trait.js
|
|
@ -74,6 +74,9 @@ function createNamedTrait( name, dfn )
|
|||
|
||||
Trait.extend = function( dfn )
|
||||
{
|
||||
// we may have been passed some additional metadata
|
||||
var meta = this.__$$meta || {};
|
||||
|
||||
// store any provided name, since we'll be clobbering it (the definition
|
||||
// object will be used to define the hidden abstract class)
|
||||
var name = dfn.__name || '(Trait)';
|
||||
|
|
@ -91,8 +94,15 @@ Trait.extend = function( dfn )
|
|||
throw Error( "Cannot instantiate trait" );
|
||||
};
|
||||
|
||||
// implement interfaces if indicated
|
||||
var base = AbstractClass;
|
||||
if ( meta.ifaces )
|
||||
{
|
||||
base = base.implement.apply( null, meta.ifaces );
|
||||
}
|
||||
|
||||
// and here we can see that traits are quite literally abstract classes
|
||||
var tclass = AbstractClass( dfn );
|
||||
var tclass = base.extend( dfn );
|
||||
|
||||
TraitType.__trait = true;
|
||||
TraitType.__acls = tclass;
|
||||
|
|
@ -114,10 +124,33 @@ Trait.extend = function( dfn )
|
|||
mixin( TraitType, dfn, tc );
|
||||
};
|
||||
|
||||
// mixes in implemented types
|
||||
TraitType.__mixinImpl = function( dest_meta )
|
||||
{
|
||||
mixinImpl( tclass, dest_meta );
|
||||
};
|
||||
|
||||
return TraitType;
|
||||
};
|
||||
|
||||
|
||||
Trait.implement = function()
|
||||
{
|
||||
var ifaces = arguments;
|
||||
|
||||
return {
|
||||
extend: function()
|
||||
{
|
||||
// pass our interface metadata as the invocation context
|
||||
return Trait.extend.apply(
|
||||
{ __$$meta: { ifaces: ifaces } },
|
||||
arguments
|
||||
);
|
||||
},
|
||||
};
|
||||
};
|
||||
|
||||
|
||||
Trait.isTrait = function( trait )
|
||||
{
|
||||
return !!( trait || {} ).__trait;
|
||||
|
|
@ -260,16 +293,71 @@ function createVirtProxy( acls, dfn )
|
|||
function mixin( trait, dfn, tc )
|
||||
{
|
||||
// the abstract class hidden within the trait
|
||||
var acls = trait.__acls,
|
||||
methods = acls.___$$methods$$;
|
||||
var acls = trait.__acls;
|
||||
|
||||
// retrieve the private member name that will contain this trait object
|
||||
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['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 ] );
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
|
|
|
|||
|
|
@ -431,9 +431,11 @@ function createMixedClass( base, traits )
|
|||
|
||||
// add each trait to the list of implemented types so that the
|
||||
// class is considered to be of type T in traits
|
||||
var impl = meta.implemented;
|
||||
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;
|
||||
|
|
|
|||
|
|
@ -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()
|
||||
{
|
||||
},
|
||||
} );
|
||||
Loading…
Reference in New Issue