closures

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 3 years ago . I want to understand in depth about closures and their mechanism of being allocated and usage. After reading and using them a while I have come up with some questions that are really eating up my head: Question - 1 How is a closure used as a variable different from a normal

问题 Playpen link: http://is.gd/EpX6lM I have a closure that takes a slice and returns a subslice of it. Compiling the following code on rust-1.0.0-beta-2 fails: trait OptionalFirst { fn optional_first<'a>(&self, x: &'a [usize]) -> &'a [usize]; } impl<F> OptionalFirst for F where F: Fn(&[usize]) -> &[usize] { fn optional_first<'a>(&self, x: &'a [usize]) -> &'a [usize] { (*self)(x) } } fn main() { let bc: Box<OptionalFirst> = Box::new( |x: &[usize]| -> &[usize] { if x.len() != 0 { &x[..1] } else {

问题 I have a JavaScript singleton object created with closure method: /** * This is the singleton. * * @namespace window.Something.Singleton */ window.Something.Singleton = (function() { /** * Foo method. * * @return {String} this method always returns with <code>bar</code> */ function _foo() { return "bar"; } /** * @lends window.Something.Singleton# */ return { /** * @borrows window.Something-_foo * @function */ foo: _foo }; }()); But the jsdoc-toolkit does not generate the inherited

问题 I am trying to instantiate and start PHPUnitTest from a closure, but I keep getting this message: mytest::authenticate_test Exception: Serialization of 'Closure' is not allowed It works outside a closure without any problems and the route is managed by Aura Router. class mytest extends TestCase { public function authenticate_test() { // ... } } $runner = 'PHPUnit_TextUI_TestRunner'; $suite = new PHPUnit_Framework_TestSuite('PHPUnit'); $suite->addTest(new mytest("authenticate_test")); $map-

问题 Trying to read this wonderful book of effective javascript(but I am still novice).. In item 13, it talks about immediately invoked function expression to create local scopes. I unfortunately however cannot wrap my head around below example function wrapElements(a) { var result = [], i, n; for ( i = 0, n = a.length; i < n; i++ ) { result[i] = function() { return a[i]; }; } return result; } var wrapped = wrapElements([10,20,30,40,50]); var f = wrapped[0]; f(); // undefined.... I really try to

问题 Here's the simplified scenario: What I do is nesting them manually. Is there an elegant implementation? class Handler { func process(_ result: String, done: @escaping (String) -> Void) { DispatchQueue.global().async { // do sth done("do something async") } } } func intercept(result: String, with handlers: [Handler], callback: @escaping (String) -> Void) { switch handlers.count { case 1: handlers[0].process(result) { r1 in callback(r1) } case 2: handlers[0].process(result) { r1 in handlers[1]

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Javascript closure inside loops - simple practical example Javascript: closure of loop? so I would like the results to be 1,2,3 instead of 3,3,3. How do I set the context/scope so that the jobs are using the correctly scoped "i"? function buildJobs(list) { var jobs = []; for (var i = 0; i < list.length; i++) { var item = list[i]; jobs.push( function() {alert(item)} ); } return jobs; } function testJobs() { var

问题 When does it make sense to use function expressions instead of function declarations when implementing "private methods"? In both cases, the functions are encapsulated, the only practical difference appears to be that I wouldn't be able to call myFunc1 in the constructor. I know I should be using the prototype property either way, but I'm just curious. function myClass { myFunc1() //error myFunc2() //success var myFunc1 = function() { } function myFunc2() { } } 回答1: You can call the function

问题 This is an extension to my previous question, which received a very explanatory answer. It turns out that I did not provide enough context to my app to make the question useful enough for my actual situation. Here is a route within my Express app: var eventbriteService = require('../apiRequests/eventbriteService'); var queue = require('queue-async'); app.get('/events', function (req, res, next) { queue() .defer(eventbriteService.getEventbriteEvents) .await(function(err, data) { if (err)

问题 <button>test</button> <button>test</button> <button>test</button> <button>test</button> <button>test</button> <script> var nodes = document.getElementsByTagName('button'); function clicked(i){ console.log('pass'); // Closure // return function(){ // console.log(i); // } } for (var i = 0; i < nodes.length; i++) { nodes[i].addEventListener('click', clicked(i)); } </script> I am try to have a fully understanding on js closure, the above function add even listener to the buttons. it console log