Promise object used to provide seperation of success and error resolution paths for async operations.
Example
var myFunc = function(){
var promise = new Promise();
//callback the promise after 10 Secs
setTimeout(hitch(promise, "callback"), 10000);
return promise.promise();
}
var myFunc2 = function(){
var promises =[];
for(var i = 0; i < 10; i++){
promises.push(myFunc);
}
//create a new promise list with all 10 promises
return new PromiseList(promises).promise();
}
myFunc.then(function(success){}, function(error){})
//chain promise operations
myFunc.chain(myfunc).then(function(success){}, function(error){})
myFunc2.then(function(success){}, function(error){})
//chain promise operations
myFunc2.chain(myfunc).then(function(success){}, function(error){})
function (){
this.__errorCbs = [];
this.__cbs = [];
}
function (){
if (!this.__fired) {
this.__fired = true;
var cbs = this.__error ? this.__errorCbs : this.__cbs,
len = cbs.length, i,
results = this.__error || this.__results;
for (i = 0; i < len; i++) {
this.__callNextTick(cbs[i], results);
}
}
}
Add a callback to the callback chain of the promise
Argumentsthe function or promise to callback when the promise is resolved.
comb.Promise this promise for chaining
function (cb){
if (cb) {
if (exports.isPromiseLike(cb)) {
cb = hitch(cb, "callback");
}
if (this.__fired && this.__results) {
this.__callNextTick(cb, this.__results);
} else {
this.__cbs.push(cb);
}
}
return this;
}
Add a callback to the errback chain of the promise
Argumentsthe function or promise to callback when the promise errors
comb.Promise this promise for chaining
function (cb){
if (cb) {
if (exports.isPromiseLike(cb)) {
cb = hitch(cb, "errback");
}
if (this.__fired && this.__error) {
this.__callNextTick(cb, this.__error);
} else {
this.__errorCbs.push(cb);
}
}
return this;
}
Adds a callback or promise to be resolved for both success and error.
Argumentscallback or promise to be resolved for both success and error.
comb.Promise this promise for chaining
function (cb){
this.addCallback(cb);
if (exports.isPromiseLike(cb)) {
this.addErrback(hitch(cb, "callback"));
} else {
this.addErrback(cb);
}
return this;
}
When called all functions registered as callbacks are called with the passed in results.
Argumentsvariable number of results to pass back to listeners of the promise
function (args){
args = argsToArray(arguments);
if (this.__fired) {
throw new Error("Already fired!");
}
this.__results = args;
this.__resolve();
return this.promise();
}
Call to chaining of promises
new Promise()
.callback("hello")
.chain(function(previousPromiseResults){
return previousPromiseResults + " world";
}, errorHandler)
.chain(function(previousPromiseResults){
return when(dbCall());
}).classic(function(err, results){
//all promises are done
});You can also use static values
new Promise().callback()
.chain("hello")
.chain(function(prev){
return prev + " world!"
}).then(function(str){
console.log(str); //"hello world!"
});If you do not provide an errback for each chain then it will be propogated to the final promise
new Promise()
.chain(function(){
return new comb.Promise().errback(new Error("error"));
})
.chain(function(){
return prev + " world!"
})
.classic(function(err, str){
console.log(err.message); //"error"
});method to call this one completes. If you return a promise the execution will delay until the returned promise has resolved.
null] : method to call if this promise errors. If errback is not specified then the returned promises errback method will be used.
comb.Promise A new that wraps the promise for chaining
function (callback,errback){
var promise = new Promise();
function errorHandler() {
var args = arguments;
if (errback) {
process.nextTick(function () {
try {
when(isFunction(errback) ? errback.apply(this, args) : errback).then(promise);
} catch (e) {
promise.errback(e);
}
});
} else {
promise.errback.apply(promise, args);
}
}
this.addCallback(function () {
var args = arguments;
process.nextTick(function () {
try {
when(isFunction(callback) ? callback.apply(this, args) : callback).then(promise.callback.bind(promise), errorHandler);
} catch (e) {
promise.errback(e);
}
});
});
// If no errback passed, then invoke our promise's errback to pass
// on to next link in the chain.
this.addErrback(errorHandler);
return promise.promise();
}
Applies the same function that returns a promise to both the callback and errback.
Argumentsfunction to call. This function must return a Promise
comb.Promise a promise to continue chaining or to resolve with.
function (callback){
var promise = new Promise();
this.addCallback(function () {
try {
when(isFunction(callback) ? callback.apply(this, arguments) : callback).then(promise);
} catch (e) {
promise.errback(e);
}
});
this.addErrback(function () {
try {
when(isFunction(callback) ? callback.apply(this, arguments) : callback).then(promise);
} catch (e) {
promise.errback(e);
}
});
return promise.promise();
}
Call this function as a classic node callback where the first argument will be an error, or null if no error occured. The other arugments will be the result from the promise.
Example
promise.classic(function(err, res){
if(err){
console.log(err);
}else{
console.log(res);
}
});
Arguments
callback where the first argument will be an error, or null if no error occured. The other arugments will be the result from the promise.
comb.Promise the promise to chain
function (cb){
if ("function" === typeof cb) {
this.addErrback(function (err) {
cb(err);
});
this.addCallback(function () {
cb.apply(this, [null].concat(argsToArray(arguments)));
});
}
return this;
}
When called all functions registered as errbacks are called with the passed in error(s)
Argumentsnumber of errors to pass back to listeners of the promise
function (args){
if (this.__fired) {
throw args || new Error("Already fired");
}
this.__error = argsToArray(arguments);
this.__resolve();
return this.promise();
}
Creates an object to that contains methods to listen to resolution but not the "callback" or "errback" methods.
Example
var asyncMethod = function(){
var ret = new comb.Promise();
process.nextTick(ret.callback.bind(ret, "hello"));
return ret.promise();
}
asyncMethod().callback() //throws error
Returns
Object an object containing "chain", "chainBoth", "promise", "addCallback", "addErrback", "then", "both".
function (){
var ret = {
chain: this.chain.bind(this),
chainBoth: this.chainBoth.bind(this),
promise: function () {
return ret;
}
};
forEach(["addCallback", "addErrback", "then", "both", "classic"], function (action) {
ret[action] = function () {
this[action].apply(this, arguments);
return ret;
}.bind(this);
}, this);
return ret;
}
Resolved a promise using the node style callback.
Example
var promise = new Promise();
fs.readFile("file.txt", "utf8", promise.resolve.bind(promise));
promise.then(function(file){
console.log(file);
});
Arguments
null] : If specified then the promise will error out
if err is null then the aruments will be used to resolve the promise.
comb.Promise for chaining.
function (err,args){
if (err) {
this.errback(err);
} else {
this.callback.apply(this, argsToArray(arguments, 1));
}
return this;
}
Call to specify action to take after promise completes or errors
Argumentsnull] : function to call after the promise completes successfully
null] : function to call if the promise errors
comb.Promise this promise for chaining
function (callback,errback){
if (exports.isPromiseLike(callback)) {
this.addCallback(callback);
this.addErrback(callback);
} else {
this.addCallback(callback);
this.addErrback(errback);
}
return this;
}
MIT https://github.com/C2FO/comb/raw/master/LICENSE
git clone git://github.com/C2FO/comb.git