lazy-initialization

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 I'm trying to lazy instantiate a UIDynamicAnimator in my code. I want to initialise it with an UIView as an IBOutlet I have. class ViewController: UIViewController { @IBOutlet var gameView : UIView @lazy var animator = UIDynamicAnimator(referenceView: gameView) ... I'm assuming this isn't working because the UIView isn't yet created because the animator property throws back an error saying it can't find the gameView. How can I get around this? 回答1: In the session video "Building Interruptible

问题 I realize that static variables are implicitly lazy , which is really great. Doing the below will not create the instance until it's first called: static var test = Test() However, assigning a new instance to the static variable initializes the original, then assigns the new instance which is troubling for me: SomeType.test = AnotherTest() //Initializes Test then AnotherTest type To give more context on what I'm trying to do, I'm trying to setup a pure Swift dependency injection using this

问题 I am working on the project which is based on hibernate and spring. I have spent two days but can't figure out why the "lazy exception" error is coming when i call this piece of code: public MemberUser SendEmail(MemberUser user) throws MailSendingException { // Check if password will be sent by mail // Hibernate.initialize(user); user = fetchService.fetch(user, FETCH); // user = userDao.load(user.getId(), FETCH); final MemberGroup group = user.getMember().getMemberGroup(); final boolean

问题 I am using some classes which need to connect to databases. The connection is only really needed when performing a real action. I want to delay the connection phase until it is really needed. For that, I want to do something similar to this: class MyClass def __init__(self): self.conn = None def connect(self): if self.conn : return self.conn = ConnectToDatabase() @connect def do_something1(self): self.conn.do_something1() @connect def do_something2(self): self.conn.do_something2() But I do

问题 What is the difference between a Lazy or Optional property in Swift? For example, if someone is building a navigation bar that comes in from the side, I think that should all be within one UIViewController . The user might never open the menu but sometimes they will. var menu: NavigationBar? lazy var menu: NavigationBar = NavigationBar.initialize() Both of the optional I think are good code, because they don't create the view unless its needed. I understand Optional means there might be a

问题 I'm trying to implement a Hibernate session/transaction interceptor to avoid LazyInitializationException on json results in Struts2, but I get this exception anyway: 245968 [http-8080-7] ERROR util.HibernateEndTransInterceptor - org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.reflect.InvocationTargetException org.apache.struts2.json.JSONException: org.apache.struts2.json

问题 I have a microsite that is utilizing Laravel and Angular. It's a one page microsite that is responsive and is broken into 5 sections. I would like to lazy load them to cut down on loading all at once. <body ng-app> <div id="wrapper"> <section id="intro">1</section> <section id="Second">2</section> <section id="Third">3</section> <section id="Fourth">4</section> <section id="Fifth">5</section> </div> </body> I'm looking to load 1 & 2 on page load then as you scroll down the page load the other