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Moved non-fallback visibility object into VisibilityObjectFactory (system does not yet use it) (#25)

closure/master
Mike Gerwitz 2011-08-11 23:11:37 -04:00
parent 91a6fb51e9
commit 79652a1120
5 changed files with 557 additions and 1 deletions

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@ -0,0 +1,24 @@
/**
* Contains fallback visibility object factory
*
* Copyright (C) 2010 Mike Gerwitz
*
* This file is part of ease.js.
*
* ease.js is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser 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 Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @author Mike Gerwitz
* @package core
*/

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@ -0,0 +1,236 @@
/**
* Contains visibility object factory
*
* Copyright (C) 2010 Mike Gerwitz
*
* This file is part of ease.js.
*
* ease.js is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser 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 Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @author Mike Gerwitz
* @package core
*/
/**
* XXX: tightly coupled
*/
var util = require( __dirname + '/util' );
/**
* Initializes visibility object factory
*
* The visibility object is the "magic" behind ease.js. This factory creates the
* object that holds the varying levels of visibility, which are swapped out and
* inherited depending on circumstance.
*/
module.exports = exports = function VisibilityObjectFactory()
{
// permit omitting 'new' keyword
if ( !( this instanceof exports ) )
{
return new exports();
}
};
/**
* Sets up properties
*
* This includes all members (including private). Private members will be set up
* in a separate object, so that they can be easily removed from the mix. That
* object will include the destination object in the prototype, so that the
* access should be transparent. This object is returned.
*
* @param {Object} dest destination object
* @param {Object} properties properties to copy
* @param {Object=} methods methods to copy
*
* @return {Object} object containing private members and dest as prototype
*/
exports.prototype.setup = function setup( dest, properties, methods )
{
// create the private layer atop of the destination object
var obj = this._createPrivateLayer( dest, properties );
// initialize each of the properties for this instance to
// ensure we're not sharing references to prototype values
this._doSetup( dest, properties[ 'public' ] );
// Do the same for protected, but only if they do not exist already in
// public. The reason for this is because the property object is laid /atop/
// of the public members, meaning that a parent's protected members will
// take precedence over a subtype's overriding /public/ members. Uh oh.
this._doSetup( dest,
properties[ 'protected' ],
methods[ 'protected' ],
'public'
);
// then add the private parts
this._doSetup( obj, properties[ 'private' ], methods[ 'private' ] );
return obj;
};
/**
* Add an extra layer atop the destination object, which will contain the
* private members
*
* The object provided will be used as the prototype for the new private layer,
* so the provided object will be accessible on the prototype chain.
*
* Subtypes may override this method to alter the functionality of the private
* visibility object (e.g. to prevent it from being created).
*
* @param {Object} atop_of object to add private layer atop of
*
* @return {Object} private layer with given object as prototype
*/
exports.prototype._createPrivateLayer = function( atop_of, properties )
{
var obj_ctor = function() {};
obj_ctor.prototype = atop_of;
// we'll be returning an instance, so that the prototype takes effect
obj = new obj_ctor();
// All protected properties need to be proxied from the private object
// (which will be passed as the context) to the object containing protected
// values. Otherwise, the protected property values would be set on the
// private object, making them inaccessible to subtypes.
this.createPropProxy( atop_of, obj, properties[ 'protected' ] );
return obj;
};
/**
* Set up destination object by copying over properties and methods
*
* @param {Object} dest destination object
* @param {Object} properties properties to copy
* @param {Object=} methods methods to copy
* @param {boolean} unless_keyword do not set if keyword is set on existing
* method
*
* @return {undefined}
*/
exports.prototype._doSetup = function(
dest, properties, methods, unless_keyword
)
{
var hasOwn = Array.prototype.hasOwnProperty,
pre = null;
// copy over the methods
if ( methods !== undefined )
{
for ( method_name in methods )
{
if ( hasOwn.call( methods, method_name ) )
{
pre = dest[ method_name ];
// If requested, do not copy the method over if it already
// exists in the destination object. Don't use hasOwn here;
// unnecessary overhead and we want to traverse any prototype
// chains. We do not check the public object directly, for
// example, because we need a solution that will work if a proxy
// is unsupported by the engine.
//
// Also note that we need to allow overriding if it exists in
// the protected object (we can override protected with
// protected). This is the *last* check to ensure a performance
// hit is incured *only* if we're overriding protected with
// protected.
if ( !unless_keyword
|| ( pre === undefined )
|| !( pre.___$$keywords$$[ unless_keyword ] )
)
{
dest[ method_name ] = methods[ method_name ];
}
}
}
}
// initialize private/protected properties and store in instance data
for ( prop in properties )
{
if ( hasOwn.call( properties, prop ) )
{
dest[ prop ] = util.clone( properties[ prop ][ 0 ] );
}
}
}
/**
* Creates a proxy for all given properties to the given base
*
* The proxy uses getters/setters to forward all calls to the base. The
* destination object will be used as the proxy. All properties within props
* will be used proxied.
*
* To summarize: for each property in props, all gets and sets will be forwarded
* to base.
*
* Please note that this does not use the JS proxy implementation. That will be
* done in the future for engines that support it.
*
* @param {Object} base object to proxy to
* @param {Object} dest object to treat as proxy (set getters/setters on)
* @param {Object} props properties to proxy
*
* @return {Object} returns dest
*/
exports.prototype.createPropProxy = function( base, dest, props )
{
var hasOwn = Object.prototype.hasOwnProperty;
for ( prop in props )
{
if ( !( hasOwn.call( props, prop ) ) )
{
continue;
}
( function( prop )
{
// just in case it's already defined, so we don't throw an error
dest[ prop ] = undefined;
// public properties, when set internally, must forward to the
// actual variable
Object.defineProperty( dest, prop, {
set: function( val )
{
base[ prop ] = val;
},
get: function()
{
return base[ prop ];
},
enumerable: true,
} );
} ).call( null, prop );
}
return dest;
};

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@ -38,6 +38,10 @@ var util = require( __dirname + '/util' ),
* object will include the destination object in the prototype, so that the * object will include the destination object in the prototype, so that the
* access should be transparent. This object is returned. * access should be transparent. This object is returned.
* *
* Properties are expected in the following format. Note that keywords are
* ignored:
* { public: { prop: [ value, { keyword: true } ] } }
*
* @param {Object} dest destination object * @param {Object} dest destination object
* @param {Object} properties properties to copy * @param {Object} properties properties to copy
* @param {Object=} methods methods to copy * @param {Object=} methods methods to copy

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@ -0,0 +1,291 @@
/**
* Tests visibility object factory
*
* Copyright (C) 2010 Mike Gerwitz
*
* This file is part of ease.js.
*
* ease.js is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser 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 Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @author Mike Gerwitz
* @package test
*/
var common = require( './common' ),
assert = require( 'assert' );
// we cannot perform these tests if it's not supported by our environment
if ( common.require( 'util' ).definePropertyFallback() )
{
return;
}
// SUT
var VisibilityObjectFactory = common.require( 'VisibilityObjectFactory' ),
sut = VisibilityObjectFactory(),
// properties are expected to be in a specific format
props = {
'public': {
pub: [ [ 'foo' ], {} ],
},
'protected': {
prot: [ [ 'bar' ], {} ],
},
'private': {
priv: [ [ 'baz' ], {} ],
},
},
methods = {
'public': {
fpub: ( function()
{
var retval = function() {};
retval.___$$keywords$$ = { 'public': true };
return retval;
} )(),
},
'protected': {
fprot: function() {},
},
'private': {
fpriv: function() {},
},
}
;
/**
* To keep with the spirit of ease.js, we should be able to instantiate
* VisibilityObjectFactory both with and without the 'new' keyword
*
* Consistency is key with these sorts of things.
*/
( function testCanInstantiateWithAndWithoutNewKeyword()
{
// with 'new' keyword
assert.ok(
( new VisibilityObjectFactory() ) instanceof VisibilityObjectFactory,
"Should be able to instantiate VisibilityObjectFactory with 'new' " +
"keyword"
);
// without 'new' keyword
assert.ok( VisibilityObjectFactory() instanceof VisibilityObjectFactory,
"Should be able to instantiate VisibilityObjectFactory without 'new' " +
"keyword"
);
} )();
/**
* One of the core requirements for proper visibility support is the ability to
* create a proxy object. Proxy objects transfer gets/sets of a certain property
* to another object. This allows objects to be layered atop each other while
* still permitting gets/sets to fall through.
*/
( function testCanCreatePropertyProxy()
{
var base = {},
dest = {},
props = { one: true, two: true, three: true },
val = 'foo',
val2 = 'bar'
;
// create proxy of props to base on dest
sut.createPropProxy( base, dest, props );
// check to ensure the properties are properly proxied
for ( prop in props )
{
dest[ prop ] = val;
// check proxy
assert.equal( dest[ prop ], val,
"Property can be set/retrieved on destination object"
);
// check base
assert.equal( base[ prop ], val,
"Property can be set via proxy and retrieved on base"
);
// set to new value
base[ prop ] = val2;
// re-check proxy
assert.equal( dest[ prop ], val2,
"Property can be set on base and retrieved on dest object"
);
}
} )();
/**
* An additional layer should be created, which will hold the private members.
*/
( function testSetupCreatesPrivateLayer()
{
var dest = { foo: [] },
obj = sut.setup( dest, props, methods );
assert.notEqual( obj, dest,
"Returned object should not be the destination object"
);
assert.strictEqual( obj.foo, dest.foo,
"Destination object is part of the prototype chain of the returned obj"
);
} )();
/**
* All protected properties must be proxied from the private layer to the
* protected. Otherwise, sets would occur on the private object, which would
* prevent them from being accessed by subtypes if set by a parent method
* invocation. (The same is true in reverse.)
*/
( function testPrivateLayerIncludesProtectedMemberProxy()
{
var dest = {},
obj = sut.setup( dest, props, methods ),
val = 'foo'
;
obj.prot = val;
assert.equal( dest.prot, val,
"Protected values are proxied from private layer"
);
} )();
/**
* Public properties should be initialized on the destination object to ensure
* that references are not shared between instances (that'd be a pretty nasty
* bug).
*
* Note that we do not care about public methods, because they're assumed to
* already be part of the prototype chain. The visibility object is only
* intended to handle levels of visibility that are not directly implemented in
* JS. Public methods are a direct consequence of adding a property to the
* prototype chain.
*/
( function testPublicPropertiesAreCopiedToDestinationObject()
{
var dest = {};
sut.setup( dest, props, methods );
// values should match
assert.equal( dest.pub[ 0 ], props[ 'public' ].pub[ 0 ],
"Public properties are properly initialized"
);
// ensure references are not shared (should be cloned)
assert.notStrictEqual( dest.pub, props[ 'public' ].pub,
"Public properties should not be copied by reference"
);
// method references should NOT be transferred (they're assumed to already
// be a part of the prototype chain, since they're outside the scope of the
// visibility object)
assert.equal( dest.fpub, undefined,
"Public method references should not be copied"
);
} )();
/**
* Protected properties should be copied over for the same reason that public
* properties should, in addition to the fact that the protected members are not
* likely to be present on the destination object. In addition, methods will be
* copied over.
*/
( function testProtectedPropertiesAndMethodsAreAddedToDestinationObject()
{
var dest = {};
sut.setup( dest, props, methods );
// values should match
assert.equal( dest.prot[ 0 ], props[ 'protected' ].prot[ 0 ],
"Protected properties are properly initialized"
);
// ensure references are not shared (should be cloned)
assert.notStrictEqual( dest.prot, props[ 'protected' ].prot,
"Protected properties should not be copied by reference"
);
// protected method references should be copied
assert.strictEqual( dest.fprot, methods[ 'protected' ].fprot,
"Protected members should be copied by reference"
);
} )();
/**
* Public members should *always* take precedence over protected. The reason for
* this is because, if a protected member is overridden and made public by a
* subtype, we need to ensure that the protected member of the supertype doesn't
* take precedence. The reason it would take precedence by default is because
* the protected visibility object is laid *atop* the public, meaning it comes
* first in the prototype chain.
*/
( function testPublicMethodsAreNotOverwrittenByProtected()
{
// use the public method
var dest = { fpub: methods[ 'public' ].fpub };
// add duplicate method to protected
methods[ 'protected' ].fpub = function() {};
sut.setup( dest, props, methods );
// ensure our public method is still referenced
assert.strictEqual( dest.fpub, methods[ 'public' ].fpub,
"Public methods should not be overwritten by protected methods"
);
} )();
/**
* Same situation with private members as protected, with the exception that we
* do not need to worry about the overlay problem (in regards to methods). This
* is simply because private members are not inherited.
*/
( function testPrivatePropertiesAndMethodsAreAddedToDestinationObject()
{
var dest = {},
obj = sut.setup( dest, props, methods );
// values should match
assert.equal( obj.priv[ 0 ], props[ 'private' ].priv[ 0 ],
"Private properties are properly initialized"
);
// ensure references are not shared (should be cloned)
assert.notStrictEqual( obj.priv, props[ 'private' ].priv,
"Private properties should not be copied by reference"
);
// private method references should be copied
assert.strictEqual( obj.fpriv, methods[ 'private' ].fpriv,
"Private members should be copied by reference"
);
} )();

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@ -29,7 +29,8 @@ TPL_VAR='/**{CONTENT}**/'
RMTRAIL="$PATH_TOOLS/rmtrail" RMTRAIL="$PATH_TOOLS/rmtrail"
# order matters # order matters
CAT_MODULES="warn prop_parser util propobj member_builder ClassBuilder" CAT_MODULES="warn prop_parser util propobj VisibilityObjectFactory"
CAT_MODULES="$CAT_MODULES member_builder ClassBuilder"
CAT_MODULES="$CAT_MODULES class class_final class_abstract interface" CAT_MODULES="$CAT_MODULES class class_final class_abstract interface"
## ##