constructor

问题 Consider two threads: threadA and threadB . (E.g. let threadA be the UI thread, and let threadB an own subclass of Thread .) Regarding data visibility , is it safe to instantiate a class in threadA , pass it to the constructor of threadB , and then use it exclusively from threadB ? Let me clarify this with code. (Note that the code is simplified, so this architecture makes sense in the real application in its actual form.) public class SomeClass { public SomeClass(....) { // initialization }

问题 I am diving deeper into Javascript, and learning how constructor methods work. In the code below, I would expect that I would be able to overwrite the constructor of an object, so that newly created instances would use the new constructor. However, I can't seem to make new instances use a new constructor. Any insight as to what is going on would be greatly appreciated! function constructorQuestion() { alert("this is the original constructor"); }; c = new constructorQuestion();

问题 Before you start to mark this as an duplicate I've already read this but my question is about MSVS compiler. The linked question talks about g++ compiler. I tried this program on MSVS 2015 compiler that is last updated on 3 Nov, 2015 here class Test { }; int main() { const Test t; } according to default initialization the above program should fail in compilation. It says that: If T is a const-qualified type, it must be a class type with a user-provided default constructor. So, diagnosis is

问题 I have a controller use API\Transformer\DataTransformer; use API\Data\DataRepositoryInterface; class DataController extends APIController implements APIInterface { protected $data; public function __construct(DataRepositoryInterface $data) { $this->data = $data; } And in the APIController use League\Fractal\Resource\Collection; use League\Fractal\Resource\Item; use League\Fractal\Manager; class APIController extends Controller { protected $statusCode = 200; public function __construct(Manager

问题 Here is a simple example of what I want : var ConstBuilder = function() { var constructor = function() {} ; constructor.prototype = {} ; return constructor ; } ; ConstBuilder.prototype = { add : function(name, value) { this.prototype[name] = value ; } } ; var A = new ConstBuilder() ; A.add('test', function() { console.log('test') ; }) ; var a = new A() ; a.test() ; This code will fail as A is not an instance of ConstBuilder (because A comes from a returned var constructor = function() {} and

问题 I've got a Problem with CodeIgniter 2.1.2 and stuck for hours try to solve it :-/ I know there are plenty(!) of threads about that, but i couldn't find a solution for my problem. I want to load a method in my constructor to check if a user is logged in, so i tried this: class my_class extends CI_Controller { public function __construct(); parent::__construct(); $this->check(); //doesn't work, endless redirection loop } "check()" is: public function check() { if (! $this->session->userdata(

问题 I'm currently having an assignment, in which i need to create a DATABASE class, which contains a employees pointers array , and private inner class , that defines employees linked list the goal to accomplish here, according to the assignment, is working acording to a DB_TYPE defined constant. when DB_TYPE = 0 i need my class methods to work with the employees pointers array , when DB_TYPE = 1 i need my class methods to work with the employees linked list . Therefore, i need two things: 1.

问题 I recently realized that in C++11 we can call a delegating initializer-list constructor like Foo() : Foo{42} // delegate to Foo(initializer_list<>) Is this syntax correct? It seems to be, although I would have expected to always use parentheses when calling a function, like Foo({42}) . The example code below compiles fine in both clang++ and g++ #include <iostream> #include <initializer_list> struct Foo { Foo() : Foo{42} // I would have expected invalid syntax, use Foo({42}) { std::cout <<

问题 So, I had a very simple case class: case class StreetSecondary1(designator: String, value: Option[String]) This was working just fine. However, I kept having places where I was parsing a single string into a tuple which was then used to build an instance of this case class: def parse1(values: String): StreetSecondary1 = { val index = values.indexOf(" ") StreetSecondary1.tupled( if (index > -1) //clip off string prior to space as designator and optionally use string after space as value

问题 Can I build a constructor to initialize a struct this way: mystruct struct1(a,b); the same way I initialize a class? Or do I have to use this way: mystruct struct1=mystruct(a,b); ? 回答1: You can use the same syntax as you use for class . In C++, there is no difference between them except for the default access specifiers which is public for struct and private for class . See here for detailed explaination: Difference between struct and class 回答2: In C++ there is no difference between a