153 lines
3.7 KiB
JavaScript
153 lines
3.7 KiB
JavaScript
/**
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* Wrapper permitting the definition of abstract classes
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*
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* This doesn't actually introduce any new functionality. Rather, it sets a
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* flag to allow abstract methods within a class, forcing users to clearly
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* state that a class is abstract.
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*
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* Copyright (C) 2010, 2011, 2013, 2014 Free Software Foundation, Inc.
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*
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* This file is part of GNU ease.js.
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*
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* ease.js is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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var Class = require( './class' );
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/**
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* Creates an abstract class
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*
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* @return {Function} abstract class
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*/
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module.exports = exports = function()
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{
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markAbstract( arguments[ arguments.length - 1 ] );
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// forward everything to Class
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var result = Class.apply( this, arguments );
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// if we're using the temporary object, then override its methods to permit
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// abstract classes
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if ( !Class.isClass( result ) )
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{
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abstractOverride( result );
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}
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return result;
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};
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/**
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* Creates an abstract class from a class extend operation
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*
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* @return {Function} abstract class
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*/
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exports.extend = function()
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{
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markAbstract( arguments[ arguments.length - 1 ] );
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return Class.extend.apply( this, arguments );
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};
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/**
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* Mixes in a trait
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*
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* @return {Object} staged abstract class
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*/
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exports.use = function()
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{
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return abstractOverride(
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Class.use.apply( this, arguments )
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);
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};
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/**
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* Creates an abstract class implementing the given members
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*
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* Simply wraps the class module's implement() method.
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*
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* @return {Object} staged abstract class
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*/
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exports.implement = function()
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{
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return abstractOverride(
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Class.implement.apply( this, arguments )
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);
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};
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/**
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* Causes a definition to be flagged as abstract
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*
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* @param {*} dfn suspected definition object
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*
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* @return {undefined}
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*/
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function markAbstract( dfn )
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{
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if ( typeof dfn === 'object' )
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{
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// mark as abstract
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dfn.___$$abstract$$ = true;
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}
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}
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/**
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* Overrides object members to permit abstract classes
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*
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* @param {Object} obj object to override
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*
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* @return {Object} obj
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*/
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function abstractOverride( obj )
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{
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var extend = obj.extend,
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impl = obj.implement,
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use = obj.use;
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// wrap and apply the abstract flag, only if the method is defined (it
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// may not be under all circumstances, e.g. after an implement())
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impl && ( obj.implement = function()
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{
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return abstractOverride( impl.apply( this, arguments ) );
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} );
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var mixin = false;
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use && ( obj.use = function()
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{
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return abstractOverride( use.apply( this, arguments ) );
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} );
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// wrap extend, applying the abstract flag
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obj.extend = function()
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{
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markAbstract( arguments[ arguments.length - 1 ] );
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return extend.apply( this, arguments );
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};
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// used by mixins; we need to mark the intermediate subtype as abstract,
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// but ensure we don't throw any errors if no abstract members are mixed
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// in (since thay may be mixed in later on)
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obj.__createBase = function()
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{
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return extend( { ___$$auto$abstract$$: true } );
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};
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return obj;
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}
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