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easejs/lib/MethodWrappers.js

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/**
* Default method wrapper functions
*
2011-12-23 00:09:01 -05:00
* Copyright (C) 2010,2011 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
*/
/**
* Method wrappers for standard (non-fallback)
* @type {Object}
*/
exports.standard = {
wrapOverride: function( method, super_method, cid, getInst )
{
return function()
{
var context = getInst( this, cid ) || this,
retval = undefined
;
// the _super property will contain the parent method (we don't
// store the previous value for performance reasons and because,
// during conventional use, it's completely unnecessary)
context.__super = super_method;
retval = method.apply( context, arguments );
// prevent sneaky bastards from breaking encapsulation by stealing
// method references (we set to undefined rather than deleting it
// because deletion causes performance degradation within V8)
context.__super = undefined;
// if the value returned from the method was the context that we
// passed in, return the actual instance (to ensure we do not break
// encapsulation)
if ( retval === context )
{
return this;
}
return retval;
};
},
wrapNew: function( method, super_method, cid, getInst )
{
return function()
{
var context = getInst( this, cid ) || this,
retval = undefined
;
// invoke the method
retval = method.apply( context, arguments );
// if the value returned from the method was the context that we
// passed in, return the actual instance (to ensure we do not break
// encapsulation)
if ( retval === context )
{
return this;
}
return retval;
};
},
Added `proxy' keyword support The concept of proxy methods will become an important, core concept in ease.js that will provide strong benefits for creating decorators and proxies, removing boilerplate code and providing useful metadata to the system. Consider the following example: Class( 'Foo', { // ... 'public performOperation': function( bar ) { this._doSomethingWith( bar ); return this; }, } ); Class( 'FooDecorator', { 'private _foo': null, // ... 'public performOperation': function( bar ) { return this._foo.performOperation( bar ); }, } ); In the above example, `FooDecorator` is a decorator for `Foo`. Assume that the `getValueOf()` method is undecorated and simply needs to be proxied to its component --- an instance of `Foo`. (It is not uncommon that a decorator, proxy, or related class will alter certain functionality while leaving much of it unchanged.) In order to do so, we can use this generic, boilerplate code return this.obj.func.apply( this.obj, arguments ); which would need to be repeated again and again for *each method that needs to be proxied*. We also have another problem --- `Foo.getValueOf()` returns *itself*, which `FooDecorator` *also* returns. This breaks encapsulation, so we instead need to return ourself: 'public performOperation': function( bar ) { this._foo.performOperation( bar ); return this; }, Our boilerplate code then becomes: var ret = this.obj.func.apply( this.obj, arguments ); return ( ret === this.obj ) ? this : ret; Alternatively, we could use the `proxy' keyword: Class( 'FooDecorator2', { 'private _foo': null, // ... 'public proxy performOperation': '_foo', } ); `FooDecorator2.getValueOf()` and `FooDecorator.getValueOf()` both perform the exact same task --- proxy the entire call to another object and return its result, unless the result is the component, in which case the decorator itself is returned. Proxies, as of this commit, accomplish the following: - All arguments are forwarded to the destination - The return value is forwarded to the caller - If the destination returns a reference to itself, it will be replaced with a reference to the caller's context (`this`). - If the call is expected to fail, either because the destination is not an object or because the requested method is not a function, a useful error will be immediately thrown (rather than the potentially cryptic one that would otherwise result, requiring analysis of the stack trace). N.B. As of this commit, static proxies do not yet function properly.
2012-05-02 13:26:47 -04:00
wrapProxy: function( proxy_to, _, cid, getInst, name, keywords )
Added `proxy' keyword support The concept of proxy methods will become an important, core concept in ease.js that will provide strong benefits for creating decorators and proxies, removing boilerplate code and providing useful metadata to the system. Consider the following example: Class( 'Foo', { // ... 'public performOperation': function( bar ) { this._doSomethingWith( bar ); return this; }, } ); Class( 'FooDecorator', { 'private _foo': null, // ... 'public performOperation': function( bar ) { return this._foo.performOperation( bar ); }, } ); In the above example, `FooDecorator` is a decorator for `Foo`. Assume that the `getValueOf()` method is undecorated and simply needs to be proxied to its component --- an instance of `Foo`. (It is not uncommon that a decorator, proxy, or related class will alter certain functionality while leaving much of it unchanged.) In order to do so, we can use this generic, boilerplate code return this.obj.func.apply( this.obj, arguments ); which would need to be repeated again and again for *each method that needs to be proxied*. We also have another problem --- `Foo.getValueOf()` returns *itself*, which `FooDecorator` *also* returns. This breaks encapsulation, so we instead need to return ourself: 'public performOperation': function( bar ) { this._foo.performOperation( bar ); return this; }, Our boilerplate code then becomes: var ret = this.obj.func.apply( this.obj, arguments ); return ( ret === this.obj ) ? this : ret; Alternatively, we could use the `proxy' keyword: Class( 'FooDecorator2', { 'private _foo': null, // ... 'public proxy performOperation': '_foo', } ); `FooDecorator2.getValueOf()` and `FooDecorator.getValueOf()` both perform the exact same task --- proxy the entire call to another object and return its result, unless the result is the component, in which case the decorator itself is returned. Proxies, as of this commit, accomplish the following: - All arguments are forwarded to the destination - The return value is forwarded to the caller - If the destination returns a reference to itself, it will be replaced with a reference to the caller's context (`this`). - If the call is expected to fail, either because the destination is not an object or because the requested method is not a function, a useful error will be immediately thrown (rather than the potentially cryptic one that would otherwise result, requiring analysis of the stack trace). N.B. As of this commit, static proxies do not yet function properly.
2012-05-02 13:26:47 -04:00
{
// it is important that we store only a boolean value as to whether or
// not this method is static *outside* of the returned closure, so as
// not to keep an unnecessary reference to the keywords object
var is_static = keywords && keywords[ 'static' ];
Added `proxy' keyword support The concept of proxy methods will become an important, core concept in ease.js that will provide strong benefits for creating decorators and proxies, removing boilerplate code and providing useful metadata to the system. Consider the following example: Class( 'Foo', { // ... 'public performOperation': function( bar ) { this._doSomethingWith( bar ); return this; }, } ); Class( 'FooDecorator', { 'private _foo': null, // ... 'public performOperation': function( bar ) { return this._foo.performOperation( bar ); }, } ); In the above example, `FooDecorator` is a decorator for `Foo`. Assume that the `getValueOf()` method is undecorated and simply needs to be proxied to its component --- an instance of `Foo`. (It is not uncommon that a decorator, proxy, or related class will alter certain functionality while leaving much of it unchanged.) In order to do so, we can use this generic, boilerplate code return this.obj.func.apply( this.obj, arguments ); which would need to be repeated again and again for *each method that needs to be proxied*. We also have another problem --- `Foo.getValueOf()` returns *itself*, which `FooDecorator` *also* returns. This breaks encapsulation, so we instead need to return ourself: 'public performOperation': function( bar ) { this._foo.performOperation( bar ); return this; }, Our boilerplate code then becomes: var ret = this.obj.func.apply( this.obj, arguments ); return ( ret === this.obj ) ? this : ret; Alternatively, we could use the `proxy' keyword: Class( 'FooDecorator2', { 'private _foo': null, // ... 'public proxy performOperation': '_foo', } ); `FooDecorator2.getValueOf()` and `FooDecorator.getValueOf()` both perform the exact same task --- proxy the entire call to another object and return its result, unless the result is the component, in which case the decorator itself is returned. Proxies, as of this commit, accomplish the following: - All arguments are forwarded to the destination - The return value is forwarded to the caller - If the destination returns a reference to itself, it will be replaced with a reference to the caller's context (`this`). - If the call is expected to fail, either because the destination is not an object or because the requested method is not a function, a useful error will be immediately thrown (rather than the potentially cryptic one that would otherwise result, requiring analysis of the stack trace). N.B. As of this commit, static proxies do not yet function properly.
2012-05-02 13:26:47 -04:00
return function()
{
var context = getInst( this, cid ) || this,
retval = undefined,
dest = ( ( is_static )
? context.$( proxy_to )
: context[ proxy_to ]
)
Added `proxy' keyword support The concept of proxy methods will become an important, core concept in ease.js that will provide strong benefits for creating decorators and proxies, removing boilerplate code and providing useful metadata to the system. Consider the following example: Class( 'Foo', { // ... 'public performOperation': function( bar ) { this._doSomethingWith( bar ); return this; }, } ); Class( 'FooDecorator', { 'private _foo': null, // ... 'public performOperation': function( bar ) { return this._foo.performOperation( bar ); }, } ); In the above example, `FooDecorator` is a decorator for `Foo`. Assume that the `getValueOf()` method is undecorated and simply needs to be proxied to its component --- an instance of `Foo`. (It is not uncommon that a decorator, proxy, or related class will alter certain functionality while leaving much of it unchanged.) In order to do so, we can use this generic, boilerplate code return this.obj.func.apply( this.obj, arguments ); which would need to be repeated again and again for *each method that needs to be proxied*. We also have another problem --- `Foo.getValueOf()` returns *itself*, which `FooDecorator` *also* returns. This breaks encapsulation, so we instead need to return ourself: 'public performOperation': function( bar ) { this._foo.performOperation( bar ); return this; }, Our boilerplate code then becomes: var ret = this.obj.func.apply( this.obj, arguments ); return ( ret === this.obj ) ? this : ret; Alternatively, we could use the `proxy' keyword: Class( 'FooDecorator2', { 'private _foo': null, // ... 'public proxy performOperation': '_foo', } ); `FooDecorator2.getValueOf()` and `FooDecorator.getValueOf()` both perform the exact same task --- proxy the entire call to another object and return its result, unless the result is the component, in which case the decorator itself is returned. Proxies, as of this commit, accomplish the following: - All arguments are forwarded to the destination - The return value is forwarded to the caller - If the destination returns a reference to itself, it will be replaced with a reference to the caller's context (`this`). - If the call is expected to fail, either because the destination is not an object or because the requested method is not a function, a useful error will be immediately thrown (rather than the potentially cryptic one that would otherwise result, requiring analysis of the stack trace). N.B. As of this commit, static proxies do not yet function properly.
2012-05-02 13:26:47 -04:00
;
// rather than allowing a cryptic error to be thrown, attempt to
// detect when the proxy call will fail and provide a useful error
// message
if ( !( ( dest !== null ) && ( typeof dest === 'object' )
&& ( typeof dest[ name ] === 'function' )
) )
Added `proxy' keyword support The concept of proxy methods will become an important, core concept in ease.js that will provide strong benefits for creating decorators and proxies, removing boilerplate code and providing useful metadata to the system. Consider the following example: Class( 'Foo', { // ... 'public performOperation': function( bar ) { this._doSomethingWith( bar ); return this; }, } ); Class( 'FooDecorator', { 'private _foo': null, // ... 'public performOperation': function( bar ) { return this._foo.performOperation( bar ); }, } ); In the above example, `FooDecorator` is a decorator for `Foo`. Assume that the `getValueOf()` method is undecorated and simply needs to be proxied to its component --- an instance of `Foo`. (It is not uncommon that a decorator, proxy, or related class will alter certain functionality while leaving much of it unchanged.) In order to do so, we can use this generic, boilerplate code return this.obj.func.apply( this.obj, arguments ); which would need to be repeated again and again for *each method that needs to be proxied*. We also have another problem --- `Foo.getValueOf()` returns *itself*, which `FooDecorator` *also* returns. This breaks encapsulation, so we instead need to return ourself: 'public performOperation': function( bar ) { this._foo.performOperation( bar ); return this; }, Our boilerplate code then becomes: var ret = this.obj.func.apply( this.obj, arguments ); return ( ret === this.obj ) ? this : ret; Alternatively, we could use the `proxy' keyword: Class( 'FooDecorator2', { 'private _foo': null, // ... 'public proxy performOperation': '_foo', } ); `FooDecorator2.getValueOf()` and `FooDecorator.getValueOf()` both perform the exact same task --- proxy the entire call to another object and return its result, unless the result is the component, in which case the decorator itself is returned. Proxies, as of this commit, accomplish the following: - All arguments are forwarded to the destination - The return value is forwarded to the caller - If the destination returns a reference to itself, it will be replaced with a reference to the caller's context (`this`). - If the call is expected to fail, either because the destination is not an object or because the requested method is not a function, a useful error will be immediately thrown (rather than the potentially cryptic one that would otherwise result, requiring analysis of the stack trace). N.B. As of this commit, static proxies do not yet function properly.
2012-05-02 13:26:47 -04:00
{
throw TypeError(
"Unable to proxy " + name + "() call to '" + proxy_to +
"'; '" + proxy_to + "' is undefined or '" + name +
"' is not a function."
);
}
retval = dest[ name ].apply( dest, arguments );
// if the object we are proxying to returns itself, then instead
// return a reference to *ourself* (so as not to break encapsulation
// and to provide a more consistent and sensible API)
return ( retval === dest )
? this
: retval;
};
},
};