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compose.js
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compose.js
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/*
* ComposeJS, object composition for JavaScript, featuring
* JavaScript-style prototype inheritance and composition, multiple inheritance,
* mixin and traits-inspired conflict resolution and composition
*/
"use strict";
(function(define){
define([], function(){
// function for creating instances from a prototype
function Create(){
}
var delegate = Object.create ?
function(proto){
return Object.create(typeof proto == "function" ? proto.prototype : proto || Object.prototype);
} :
function(proto){
Create.prototype = typeof proto == "function" ? proto.prototype : proto;
var instance = new Create();
Create.prototype = null;
return instance;
};
// this does the work of combining mixins/prototypes
function mixin(instance, args, i){
// use prototype inheritance for first arg
var value, argsLength = args.length;
for(; i < argsLength; i++){
var arg = args[i];
if(typeof arg == "function"){
// the arg is a function, use the prototype for the properties
arg = arg.prototype;
for(var key in arg){
value = arg[key];
if(typeof value == "function" && key in instance && value !== instance[key]){
value = resolvePrototype(value, key, instance[key], arg.hasOwnProperty(key), instance);
}
if(value && value.install){
// apply modifier
value.install.call(instance, key);
}else{
instance[key] = value;
}
}
}else{
// it is an object, copy properties, looking for modifiers
for(var key in arg){
var value = arg[key];
if(typeof value == "function"){
if(value.install){
// apply modifier
value.install.call(instance, key);
continue;
}
if(key in instance){
if(value == required){
// required requirement met
continue;
}
if(!value.overrides){
// add the overrides chain
value.overrides = instance[key];
}
}
}
// add it to the instance
instance[key] = value;
}
}
}
return instance;
}
// allow for override (by es5 module)
Compose._setMixin = function(newMixin){
mixin = newMixin;
};
function resolvePrototype(value, key, existing, own, instance){
if(value == required){
// it is a required value, and we have satisfied it
return existing;
}
else if(own){
// if it is own property, it is considered an explicit override
if(!value.overrides){
// record the override hierarchy
value.overrides = instance[key];
}
}else{
// still possible conflict, see if either value is in the other value's override chain
var overriden = value;
while((overriden = overriden.overrides) != existing){
if(!overriden){
// couldn't find existing in the provided value's override chain
overriden = existing;
while((overriden = overriden.overrides) != value){
if(!overriden){
// couldn't find value in the provided existing's override chain
// we have a real conflict now
existing = function(){
throw new Error("Conflicted method, final composer must explicitly override with correct method.");
}
break;
}
}
// use existing, since it overrides value
value = existing;
break;
}
}
}
return value;
}
Compose._resolvePrototype = resolvePrototype;
// Decorator branding
function Decorator(install){
function Decorator(){
throw new Error("Decorator not applied");
}
Decorator.install = install;
return Decorator;
}
Compose.Decorator = Decorator;
// aspect applier
function aspect(handler){
return function(advice){
return Decorator(function(key){
var baseMethod = this[key];
if(baseMethod && !(baseMethod.install)){
// applying to a plain method
this[key] = handler(this, baseMethod, advice);
}else{
this[key] = Compose.around(function(topMethod){
baseMethod && baseMethod.install.call(this, key);
return handler(this, this[key], advice);
});
}
});
};
};
// around advice, useful for calling super methods too
Compose.around = aspect(function(target, base, advice){
return advice.call(target, base);
});
Compose.before = aspect(function(target, base, advice){
return function(){
var results = advice.apply(this, arguments);
if(results !== stop){
return base.apply(this, results || arguments);
}
};
});
var stop = Compose.stop = {};
var undefined;
Compose.after = aspect(function(target, base, advice){
return function(){
var results = base.apply(this, arguments);
var adviceResults = advice.apply(this, arguments);
return adviceResults === undefined ? results : adviceResults;
};
});
// rename Decorator for calling super methods
Compose.from = function(trait, fromKey){
if(fromKey){
return (typeof trait == "function" ? trait.prototype : trait)[fromKey];
}
return Decorator(function(key){
if(!(this[key] = (typeof trait == "string" ? this[trait] :
(typeof trait == "function" ? trait.prototype : trait)[fromKey || key]))){
throw new Error("Source method " + fromKey + " was not available to be renamed to " + key);
}
});
};
// Composes an instance
Compose.create = function(base){
// create the instance
var instance = mixin(delegate(base), arguments, 1);
var argsLength = arguments.length;
// for go through the arguments and call the constructors (with no args)
for(var i = 0; i < argsLength; i++){
var arg = arguments[i];
if(typeof arg == "function"){
instance = arg.call(instance) || instance;
}
}
return instance;
}
// The required function, just throws an error if not overriden
function required(){
throw new Error("This method is required and no implementation has been provided");
};
Compose.required = required;
// get the value of |this| for direct function calls for this mode (strict in ES5)
function extend(){
var args = [this];
args.push.apply(args, arguments);
return Compose.apply(0, args);
}
// Compose a constructor
function Compose(base){
var args = arguments;
var prototype = (args.length < 2 && typeof args[0] != "function") ?
args[0] : // if there is just a single argument object, just use that as the prototype
mixin(delegate(base), args, 1); // normally create a delegate to start with
function Constructor(){
var instance;
if(this instanceof Constructor){
// called with new operator, can proceed as is
instance = this;
}else{
// we allow for direct calls without a new operator, in this case we need to
// create the instance ourself.
Create.prototype = prototype;
instance = new Create();
}
// call all the constructors with the given arguments
for(var i = 0; i < constructorsLength; i++){
var constructor = constructors[i];
var result = constructor.apply(instance, arguments);
if(typeof result == "object"){
if(result instanceof Constructor){
instance = result;
}else{
for(var j in result){
if(result.hasOwnProperty(j)){
instance[j] = result[j];
}
}
}
}
}
return instance;
}
Constructor._getConstructors = function(){
return constructors;
};
var constructors = getConstructors(arguments),
constructorsLength = constructors.length;
Constructor.extend = extend;
Constructor.prototype = prototype;
return Constructor;
};
Compose.apply = function(thisObject, args){
// apply to the target
return thisObject ?
mixin(thisObject, args, 0) : // called with a target object, apply the supplied arguments as mixins to the target object
extend.apply.call(Compose, 0, args); // get the Function.prototype apply function, call() it to apply arguments to Compose (the extend doesn't matter, just a handle way to grab apply, since we can't get it off of Compose)
};
Compose.call = function(thisObject){
// call() should correspond with apply behavior
return mixin(thisObject, arguments, 1);
};
function getConstructors(args){
// this function registers a set of constructors for a class, eliminating duplicate
// constructors that may result from diamond construction for classes (B->A, C->A, D->B&C, then D() should only call A() once)
var constructors = [];
function iterate(args, checkChildren){
outer:
for(var i = 0; i < args.length; i++){
var arg = args[i];
if(typeof arg == "function"){
if(checkChildren && arg._getConstructors){
iterate(arg._getConstructors()); // don't need to check children for these, this should be pre-flattened
}else{
for(var j = 0; j < constructors.length; j++){
if(arg == constructors[j]){
continue outer;
}
}
constructors.push(arg);
}
}
}
}
iterate(args, true);
return constructors;
}
// returning the export of the module
return Compose;
});
})(typeof define != "undefined" ?
define: // AMD/RequireJS format if available
function(deps, factory){
if(typeof module !="undefined"){
module.exports = factory(); // CommonJS environment, like NodeJS
// require("./configure");
}else{
Compose = factory(); // raw script, assign to Compose global
}
});