Question

我有以下C ++类：

class DEF
{
   //...
}

class ABC
{
   public:
      DEF my_def;
      ~ABC();
   //...
}

某处：

ABC* abc = new ABC(...);
delete abc;

我的问题：

调用delete abc后是否可以访问my_def？在删除后abc->my_def.somefunc() 安全吗？ -

Answer 1

不，在let task = NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: { // Don't put other code before this next line, it is defining the closure we just started with the "{" (data, response, error) -> Void in // This is where the closure body begins print(NSThread.isMainThread()) // false (unless you've set the delegate queue to be the main queue) // Example of processing the return value let dataString = NSString.init(data: data!, encoding: NSUTF8StringEncoding) print(dataString) // Okay to do work with this here, but don't do any UI work. // Jump back over to the main queue to do any UI updates // UI updates must always be done on the main queue dispatch_async(dispatch_get_main_queue(), { print(NSThread.isMainThread()) // true (we told it to execute this new block on the main queue) // Execute the code to update your UI (change your view) from here myCoolUIUpdatingMethod(dataString) }); // anything down here could be executed before the dispatch_async block completes // dispatch_sync would block this thread until its block completes }); // run the task task.resume() // your program's main thread will not be blocked while the load is in progress的析构函数运行后，其成员将按其声明的相反顺序销毁。删除abc后，其所有内存都将被释放。这包括您示例中的abc。

也许这个问题对您有用：What is a smart pointer and when should I use one?

附录：C ++的一个主要问题是undefined behavior。如果在此期间内存未被重用，则use-after-free等编程错误可能会在80％的时间内起作用。但是你可能会覆盖不相关的内存和/或允许读取外来数据。这是一个严重的安全问题，崩溃的程序是你现在最好的希望。

公共成员变量何时死亡？

1 个答案: