Async all around us (promises)
Download as PPTX, PDF0 likes1,094 views
The document discusses asynchronous programming concepts like promises, futures, and callbacks in different programming languages like JavaScript, Java, Dart. It provides examples of how to handle asynchronous operations and pass arguments between asynchronous functions. It emphasizes the importance of testing asynchronous code through unit tests.
![MY CODE DOESN’T WORK
exports.saveWeekAvailability = function(req, res){
console.log("-- SAVE WEEK AVAILABILITY --");
weekData = req.body;
var resultArr = [];
for (var i=0; i< weekData.length; i++) {
resultArr[i] = Availability(weekData[i]).save(function(err, result){
return result;
});
}
console.log("-- Result Arr --");
console.log(resultArr);
};](https://image.slidesharecdn.com/jspromises-140925090546-phpapp02/85/Async-all-around-us-promises-7-320.jpg)
![MY CODE DOESN’T WORK
resultArr[i] = Availability(weekData[i]).save(function(err, result){
return result;
});](https://image.slidesharecdn.com/jspromises-140925090546-phpapp02/85/Async-all-around-us-promises-8-320.jpg)
Async all around us (promises)
- 1. ASYNC ALL AROUND US FRANCISCO MS FERREIRA @fmsf303
- 2. JS Promises
- 3. Java Completable Futures JS Promises
- 4. Dart Futures Java Completable Futures JS Promises
- 7. MY CODE DOESN’T WORK exports.saveWeekAvailability = function(req, res){ console.log("-- SAVE WEEK AVAILABILITY --"); weekData = req.body; var resultArr = []; for (var i=0; i< weekData.length; i++) { resultArr[i] = Availability(weekData[i]).save(function(err, result){ return result; }); } console.log("-- Result Arr --"); console.log(resultArr); };
- 8. MY CODE DOESN’T WORK resultArr[i] = Availability(weekData[i]).save(function(err, result){ return result; });
- 9. MY CODE DOESN’T WORK router.get('/about', function(req, res) { var animalsData = sequelize.query("SELECT * FROM animals").success(function(rows) { return rows; }); console.log(animals); // returns 'undefined' var humansData = sequelize.query("SELECT * FROM humans").success(function(rows) { return rows; }); console.log(humans); // returns 'undefined' res.render('about', { animals: animalsData, humans: humansData }); });
- 10. PYRAMID OF DOOM router.get('/about', function(req, res) { sequelize.query("SELECT * FROM animals").success( function( animals ) { sequelize.query("SELECT * FROM humans").success( function( humans ) { res.render('about', { animals: animalsData, humans: humansData }); }); }); });
- 13. JAVA public CompletableFuture<String> ask() { final CompletableFuture<String> future = new CompletableFuture<>(); //... return future; }
- 14. JAVA public CompletableFuture<String> ask() { final CompletableFuture<String> future = new CompletableFuture<>(); //... return future; } future.complete("42");
- 15. JAVA public CompletableFuture<String> ask() { final CompletableFuture<String> future = new CompletableFuture<>(); //... return future; } future.complete("42"); future.get(); // this will block execution
- 16. DART void printDailyNewsDigest() { File file = new File("dailyNewsDigest.txt"); Future future = file.readAsString(); future.then((content) { print(content); }); }
- 17. DART Future<Item> getItem(){ var completer = new Completer(); // At some time you need to complete the future: completer.complete(new Item()); return completer.future; }
- 18. PROMISES this.updateEmailsInDatabase = function() { var fetchEmailDeferer = Q.defer(); inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done(); return fetchEmailDeferer.promise; };
- 19. PROMISES this.updateEmailsInDatabase = function() { var fetchEmailDeferer = Q.defer(); inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done(); return fetchEmailDeferer.promise; };
- 20. PROMISES this.updateEmailsInDatabase = function() { var fetchEmailDeferer = Q.defer(); inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done(); return fetchEmailDeferer.promise; };
- 21. PROMISES this.updateEmailsInDatabase = function() { var fetchEmailDeferer = Q.defer(); inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done(); return fetchEmailDeferer.promise; };
- 22. PROMISES this.updateEmailsInDatabase = function() { var fetchEmailDeferer = Q.defer(); inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done(); return fetchEmailDeferer.promise; };
- 23. PROMISES this.updateEmailsInDatabase = function() { var fetchEmailDeferer = Q.defer(); inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done(); return fetchEmailDeferer.promise; };
- 24. PROMISES this.updateEmailsInDatabase = function() { var fetchEmailDeferer = Q.defer(); inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done(); return fetchEmailDeferer.promise; };
- 25. PROMISES this.updateEmailsInDatabase = function() { var fetchEmailDeferer = Q.defer(); inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done(); return fetchEmailDeferer.promise; };
- 26. WHAT IS A PROMISE? - Like a future - I promise that I will resolve a value
- 27. WHAT IS A PROMISE? - Like a future - I promise that I will resolve a value - function fooBar() { - …; - return promise; - }
- 28. WHAT IS A PROMISE? - Like a future - I promise that I will resolve a value - function fooBar() { - var deferer = Q.defer() - functionWithACallback( function( aValue) { - deferer.resolve( aValue ); - } - return defer.promise; - } - var promise = fooBar();
- 29. WHAT IS A PROMISE? - Like a future - I promise that I will resolve a value - function fooBar() { - var deferer = Q.defer() - functionWithACallback( function( aValue) { - deferer.resolve( aValue ); - } - return defer.promise; - } - var promise = fooBar();
- 30. WHAT IS A PROMISE? - Like a future - I promise that I will resolve a value - function fooBar() { - var deferer = Q.defer() - functionWithACallback( function( aValue) { - deferer.resolve( aValue ); - } - return defer.promise; - } - var promise = fooBar(); - promise.then( function( value ) { - console.log( “myValue:”, value ); - });
- 31. ARGUMENTS
- 32. ARGUMENT FLOW inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done(); messages listMessages saveMessagesFromEmailServerLocally
- 33. ARGUMENT FLOW inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done(); listMessages saveMessagesFromEmailServerLocally fetchEmailDeferer.resolve messages success
- 35. BI-DIRECTIONAL ARGUMENTS databasePromise .then( openCollection( dbconfig.getUsersCollectionName() ) ) .then( insert(user) ) .then( addUserDeferer.resolve ) .done();
- 36. BI-DIRECTIONAL ARGUMENTS databasePromise .then( openCollection( dbconfig.getUsersCollectionName() ) ) .then( insert(user) ) .then( addUserDeferer.resolve ) .done(); databasePromise openCollection getCollection database db collection
- 37. BI-DIRECTIONAL ARGUMENTS //.then( openCollection( dbconfig.getUsersCollectionName() ) ) function openCollection( colectionToOpen ) { return function(db) { return db.collection( colectionToOpen ); }; } databasePromise openCollection getCollection database db collection
- 38. BI-DIRECTIONAL ARGUMENTS //.then( openCollection( dbconfig.getUsersCollectionName() ) ) function openCollection( colectionToOpen ) { return function(db) { return db.collection( colectionToOpen ); }; } databasePromise openCollection getCollection database db collection
- 39. BI-DIRECTIONAL ARGUMENTS //.then( openCollection( dbconfig.getUsersCollectionName() ) ) function openCollection( colectionToOpen ) { return function(db) { return db.collection( colectionToOpen ); }; } databasePromise openCollection getCollection database db collection
- 41. TEST YOUR STUFF!
- 42. PLEASE TEST YOUR STUFF!
- 43. UNIT TESTS IMPACT IN JS inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) it('should be able to list messages', function( done ) { inboxHandler.listMessages( 2 ).then( function( messages ) { messages.should.have.length( 2 ); }).done( done ); });
- 44. READABLE & MAINTAINABLE inboxHandler .listMessages() .then( saveMessagesFromEmailServerLocally ) .then( fetchEmailDeferer.resolve ) .done();