closures

问题 I'm trying to gather thumbnails of all the user's images into an array, but when I call the enumerateAssetsUsingBlock method of ALAssetsLibrary nothing seems to happen. import UIKit import AssetsLibrary class ViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate { @IBOutlet var photoLibView: UICollectionView var assetLibrary : ALAssetsLibrary = ALAssetsLibrary() func showCustomLibrary() { self.assetLibrary = ALAssetsLibrary() var assetsArray :

问题 It all started with these simple lines of code: a = 3; b = 2; function line(x) { var a = 5; var b = 4; return a*x+b; } // returns 17 b = line(a) - b; alert(b); // returns 36 c = line(a) + b; alert(c); Both alerts return 17 and 36, respectively. The control works as expected. Until… I make the mistake of changing the inside of the function like so: function line(x) { var a = 5; b = 4; return a*x+b; } Suddenly line 13 returns 15, line 17 returns 23 and the situation continues to deteriorate as

问题 I've been developing with JS for a while, and while I know that code below works, I don't really understand why it works. The way I see it, I've defined testString in testClosure function, and I'm expecting that variable to 'go away' when testClosure function is done, since it's local variable. However, when I call inner function with a timer, it's still aware of testString variable. Why? Isn't that variable gone five seconds ago when testClosure finished executing? Does the inner function

问题 I got this error when I Run my Shiny app on my laptop. App worked before I added a line of code with library(git2r). Below my code. Can anyone assist? Thanks. ui.R league_desc <- c("Premier League","Serie A","Bundesliga","La Liga") shinyUI( fluidPage( headerPanel(h1('Football Statistics', align = "center"), h2('Data on the 4 main european football leagues. Period 2011 - 2015', align = "center")), sidebarPanel( h4('Selection Parameters', align = "center"), This is the initial part of my ui.R

问题 foreach(var category in categories) { a.AddRange(_db.Articles.Where(c => c.Categories.Contains(category))); } The code runs fine, yet I get a warning about "access to modified closure" in reference to category used in the lambda expression. Question: Is the warning of any consequence in this circumstance? 回答1: The warning here is because you are accessing the variable category inside the closure for the Where lambda. The value category changes with every iteration and Where is delay executed

问题 This is my code in obj-c: __block NSString *requestReference = [self operation:method url:url parameters:parameters headers:headers success:^(NSURLSessionDataTask *task, id responseObject) { NSError *error = [NSError errorWithSessionTask:task responseObject:responseObject]; if (error) { NSLog(@"error - %@", error); [delegate requestWithReference:requestReference didFinishWithBusinessError:error]; } else { id responseModel; if (modelClass && responseObject) { if ([responseObject isKindOfClass:

问题 This question already has an answer here : Is there a workaround for $this within a closure in PHP 5.3? (1 answer) Closed 3 years ago . I have code like this: class Foo { var $callbacks = array(); function __construct() { $this->callbacks[] = function($arg) { return $this->bar($arg); }; } function bar($arg) { return $arg * $arg; } } and I would like to use $this inside closures, I've try to add use ($this) but this throw error: Cannot use $this as lexical variable 回答1: You cannot use $this as

问题 I have an already defined closure and I want to inject code inside when I execute it. Here is an example: $predefined = "print 'my predefined injected code<br />';"; $closure = function () { print 'hello<br />'; }; call_user_func_array($closure, array()); // output : hello I want to mix 2 codes : a predefined one and the closure's one. After modification, I want my closure to look like this $closure = function () { print 'my predefined injected code<br />'; print 'hello<br />'; }; Is it

问题 I can't work out how to update a global variable from within YUI3. Consider the following code: window.myVariable = 'data-one'; var yuiWrap = YUI().use('node',function(Y) { console.log(window.myVariable); // 'data-one' window.myVariable = 'data-two'; console.log(window.myVariable); // 'data-two' }); console.log(window.myVariable); // 'data-one' Can anyone explain this to me? It's causing me a lot of trouble. Why can window.myVariable be accessed but not properly updated from within a YUI3

问题 I searched a lot and haven't found anything that really helped to solve my problem... I'm trying to build a simple UIControl from scratch, like a UIButton. It can't be subclass of UIControl for particular reasons. I need this control to do something like this: myControl.addTarget(target: AnyObject?, action: Selector, forControlEvents: UIControlEvents) The problem is that the implementation of the method that execute this selector when the button is touched needs the "performSelector:" method.