I am using a node.js module that has a method without callbacks. Instead of it, has an event that fires when that method has finished. I want resolve a promise, using that event as callback securing me that method has been completed succesfully.
array.lenght on promise can be X. So, I need 'hear' X times the event to secure me that all methods has completed succesfully <-- This is not the problem, I am just telling you that I know this could happen
Event :
tf2.on('craftingComplete', function(recipe, itemsGained){
if(recipe == -1){
console.log('CRAFT FAILED')
}
else{
countOfCraft++;
console.log('Craft completed! Got a new Item #'+itemsGained);
}
})
Promise:
const craftWepsByClass = function(array, heroClass){
return new Promise(function (resolve, reject){
if(array.length < 2){
console.log('Done crafting weps of '+heroClass);
return resolve();
}
else{
for (var i = 0; i < array.length; i+=2) {
tf2.craft([array[i].id, array[i+1].id]); // <--- this is the module method witouth callback
}
return resolve(); // <---- I want resolve this, when all tf2.craft() has been completed. I need 'hear' event many times as array.length
}
})
}
I am using a node.js module that has a method without callbacks. Instead of it, has an event that fires when that method has finished. I want resolve a promise, using that event as callback securing me that method has been completed succesfully.
array.lenght on promise can be X. So, I need 'hear' X times the event to secure me that all methods has completed succesfully <-- This is not the problem, I am just telling you that I know this could happen
Event :
tf2.on('craftingComplete', function(recipe, itemsGained){
if(recipe == -1){
console.log('CRAFT FAILED')
}
else{
countOfCraft++;
console.log('Craft completed! Got a new Item #'+itemsGained);
}
})
Promise:
const craftWepsByClass = function(array, heroClass){
return new Promise(function (resolve, reject){
if(array.length < 2){
console.log('Done crafting weps of '+heroClass);
return resolve();
}
else{
for (var i = 0; i < array.length; i+=2) {
tf2.craft([array[i].id, array[i+1].id]); // <--- this is the module method witouth callback
}
return resolve(); // <---- I want resolve this, when all tf2.craft() has been completed. I need 'hear' event many times as array.length
}
})
}
4 Answers
Reset to default 9At first lets promisify the crafting:
function craft(elem){
//do whatever
return Promise((resolve,reject) =>
tf2.on('craftingComplete', (recipe,itemsGained) =>
if( recipe !== -1 ){
resolve(recipe, itemsGained);
}else{
reject("unsuccessful");
}
})
);
}
So to craft multiples then, we map our array to promises and use Promise.all:
Promise.all( array.map( craft ) )
.then(_=>"all done!")
If the events will be fired in the same order as the respective craft() calls that caused them, you can use a queue:
var queue = []; // for the tf2 instance
function getNextTf2Event() {
return new Promise(resolve => {
queue.push(resolve);
});
}
tf2.on('craftingComplete', function(recipe, itemsGained) {
var resolve = queue.shift();
if (recipe == -1) {
resolve(Promise.reject(new Error('CRAFT FAILED')));
} else {
resolve(itemsGained);
}
});
function craftWepsByClass(array, heroClass) {
var promises = [];
for (var i = 1; i < array.length; i += 2) {
promises.push(getNextTf2Event().then(itemsGained => {
console.log('Craft completed! Got a new Item #'+itemsGained);
// return itemsGained;
}));
tf2.craft([array[i-1].id, array[i].id]);
}
return Promise.all(promises).then(allItemsGained => {
console.log('Done crafting weps of '+heroClass);
return …;
});
}
If you don't know anything about the order of the events, and there can be multiple concurrent calls to craftWepsByClass, you cannot avoid a global counter (i.e. one linked to the tf2 instance). The downside is that e.g. in two overlapping calls a = craftWepsByClass(…), b = craftWepsByClass() the a promise won't be resolved until all crafting of the second call is completed.
var waiting = []; // for the tf2 instance
var runningCraftings = 0;
tf2.on('craftingComplete', function(recipe, itemsGained) {
if (--runningCraftings == 0) {
for (var resolve of waiting) {
resolve();
}
waiting.length = 0;
}
if (recipe == -1) {
console.log('CRAFT FAILED')
} else {
console.log('Craft completed! Got a new Item #'+itemsGained);
}
});
function craftWepsByClass(array, heroClass) {
for (var i = 1; i < array.length; i += 2) {
runningCraftings++;
tf2.craft([array[i-1].id, array[i].id]);
}
return (runningCraftings == 0
? Promise.resolve()
: new Promise(resolve => {
waiting.push(resolve);
})
).then(() => {
console.log('Done crafting weps of '+heroClass);
});
}
Of course in both solutions you must be 100% certain that each call to craft() causes exactly one event.
You can look at the event-as-promise package. It convert events into Promise continuously until you are done with all the event processing.
When combined with async/await, you can write for-loop or while-loop easily with events. For example, we want to process data event until it return null.
const eventAsPromise = new EventAsPromise();
emitter.on('data', eventAsPromise.eventListener);
let done;
while (!done) {
const result = await eventAsPromise.upcoming();
// Some code to process the event result
process(result);
// Mark done when no more results
done = !result;
}
emitter.removeListener('data', eventAsPromise.eventListener);
If you are proficient with generator function, it may looks a bit simpler with this.
const eventAsPromise = new EventAsPromise();
emitter.on('data', eventAsPromise.eventListener);
for (let promise of eventAsPromise) {
const result = await promise;
// Some code to process the event result
process(result);
// Stop when no more results
if (!result) {
break;
}
}
emitter.removeListener('data', eventAsPromise.eventListener);
I need check if event 'craftingComplete' has fired many times as I call tf2.craft. Doesnt matters any posible ID or if craft has failed. I need to know if tf2.craft has finished and only why is checking 'craftingComplete' event
Given that we know i within for loop will be incremented i += 2 where i is less than .length of array, we can create a variable equal to that number before the for loop and compare i to the number within event handler
const craftWepsByClass = function(array, heroClass) {
return new Promise(function(resolve, reject) {
var countCraft = 0;
var j = 0;
var n = 0;
for (; n < array.length; n += 2);
tf2.on('craftingComplete', function(recipe, itemsGained) {
if (recipe == -1) {
console.log('CRAFT FAILED')
} else {
countOfCraft++;
console.log('Craft completed! Got a new Item #' + itemsGained);
if (j === n) {
resolve(["complete", craftCount])
}
}
})
if (array.length < 2) {
console.log('Done crafting weps of ' + heroClass);
return resolve();
} else {
try {
for (var i = 0; i < array.length; i += 2, j += 2) {
tf2.craft([array[i].id, array[i + 1].id]);
}
} catch (err) {
console.error("catch", err);
throw err
}
}
})
}
craftWepsByClass(array, heroClass)
.then(function(data) {
console.log(data[0], data[1])
})
.catch(function(err) {
console.error(".catch", err)
})
tf2.craft()return aPromise? Note, aPromisecan only be resolved or rejected once. – guest271314 Commented Oct 18, 2017 at 19:45that has a method without callbacks.wellonis a callback.. :) – Keith Commented Oct 18, 2017 at 19:49