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|
define("dojo/aspect", [], function(){
// TODOC: after/before/around return object
// TODOC: after/before/around param types.
/*=====
dojo.aspect = {
// summary: provides aspect oriented programming functionality, allowing for
// one to add before, around, or after advice on existing methods.
//
// example:
// | define(["dojo/aspect"], function(aspect){
// | var signal = aspect.after(targetObject, "methodName", function(someArgument){
// | this will be called when targetObject.methodName() is called, after the original function is called
// | });
//
// example:
// The returned signal object can be used to cancel the advice.
// | signal.remove(); // this will stop the advice from being executed anymore
// | aspect.before(targetObject, "methodName", function(someArgument){
// | // this will be called when targetObject.methodName() is called, before the original function is called
// | });
after: function(target, methodName, advice, receiveArguments){
// summary: The "after" export of the aspect module is a function that can be used to attach
// "after" advice to a method. This function will be executed after the original method
// is executed. By default the function will be called with a single argument, the return
// value of the original method, or the the return value of the last executed advice (if a previous one exists).
// The fourth (optional) argument can be set to true to so the function receives the original
// arguments (from when the original method was called) rather than the return value.
// If there are multiple "after" advisors, they are executed in the order they were registered.
// target: Object
// This is the target object
// methodName: String
// This is the name of the method to attach to.
// advice: Function
// This is function to be called after the original method
// receiveArguments: Boolean?
// If this is set to true, the advice function receives the original arguments (from when the original mehtod
// was called) rather than the return value of the original/previous method.
// returns:
// A signal object that can be used to cancel the advice. If remove() is called on this signal object, it will
// stop the advice function from being executed.
},
before: function(target, methodName, advice){
// summary: The "before" export of the aspect module is a function that can be used to attach
// "before" advice to a method. This function will be executed before the original method
// is executed. This function will be called with the arguments used to call the method.
// This function may optionally return an array as the new arguments to use to call
// the original method (or the previous, next-to-execute before advice, if one exists).
// If the before method doesn't return anything (returns undefined) the original arguments
// will be preserved.
// If there are multiple "before" advisors, they are executed in the reverse order they were registered.
//
// target: Object
// This is the target object
// methodName: String
// This is the name of the method to attach to.
// advice: Function
// This is function to be called before the original method
},
around: function(target, methodName, advice){
// summary: The "around" export of the aspect module is a function that can be used to attach
// "around" advice to a method. The advisor function is immediately executed when
// the around() is called, is passed a single argument that is a function that can be
// called to continue execution of the original method (or the next around advisor).
// The advisor function should return a function, and this function will be called whenever
// the method is called. It will be called with the arguments used to call the method.
// Whatever this function returns will be returned as the result of the method call (unless after advise changes it).
//
// example:
// If there are multiple "around" advisors, the most recent one is executed first,
// which can then delegate to the next one and so on. For example:
// | around(obj, "foo", function(originalFoo){
// | return function(){
// | var start = new Date().getTime();
// | var results = originalFoo.apply(this, arguments); // call the original
// | var end = new Date().getTime();
// | console.log("foo execution took " + (end - start) + " ms");
// | return results;
// | };
// | });
//
// target: Object
// This is the target object
// methodName: String
// This is the name of the method to attach to.
// advice: Function
// This is function to be called around the original method
}
};
=====*/
"use strict";
var nextId = 0;
function advise(dispatcher, type, advice, receiveArguments){
var previous = dispatcher[type];
var around = type == "around";
var signal;
if(around){
var advised = advice(function(){
return previous.advice(this, arguments);
});
signal = {
remove: function(){
signal.cancelled = true;
},
advice: function(target, args){
return signal.cancelled ?
previous.advice(target, args) : // cancelled, skip to next one
advised.apply(target, args); // called the advised function
}
};
}else{
// create the remove handler
signal = {
remove: function(){
var previous = signal.previous;
var next = signal.next;
if(!next && !previous){
delete dispatcher[type];
}else{
if(previous){
previous.next = next;
}else{
dispatcher[type] = next;
}
if(next){
next.previous = previous;
}
}
},
id: nextId++,
advice: advice,
receiveArguments: receiveArguments
};
}
if(previous && !around){
if(type == "after"){
// add the listener to the end of the list
var next = previous;
while(next){
previous = next;
next = next.next;
}
previous.next = signal;
signal.previous = previous;
}else if(type == "before"){
// add to beginning
dispatcher[type] = signal;
signal.next = previous;
previous.previous = signal;
}
}else{
// around or first one just replaces
dispatcher[type] = signal;
}
return signal;
}
function aspect(type){
return function(target, methodName, advice, receiveArguments){
var existing = target[methodName], dispatcher;
if(!existing || existing.target != target){
// no dispatcher in place
target[methodName] = dispatcher = function(){
var executionId = nextId;
// before advice
var args = arguments;
var before = dispatcher.before;
while(before){
args = before.advice.apply(this, args) || args;
before = before.next;
}
// around advice
if(dispatcher.around){
var results = dispatcher.around.advice(this, args);
}
// after advice
var after = dispatcher.after;
while(after && after.id < executionId){
results = after.receiveArguments ? after.advice.apply(this, args) || results :
after.advice.call(this, results);
after = after.next;
}
return results;
};
if(existing){
dispatcher.around = {advice: function(target, args){
return existing.apply(target, args);
}};
}
dispatcher.target = target;
}
var results = advise((dispatcher || existing), type, advice, receiveArguments);
advice = null;
return results;
};
}
return {
before: aspect("before"),
around: aspect("around"),
after: aspect("after")
};
});
|
