constructor

问题 When you create an object with a constructor it has a constructor property pointing to the constructor function: var Foo = function(foo) { this.foo = foo; } var myFoo = new Foo(123); myFoo.constructor === Foo; // true After creating this object I can change Foo.prototype ... Foo.prototype.x = 'y'; ... or reassign a new prototype object: Foo.prototype = { num: 99 }; myFoo.constructor === Foo; // still true But if I create a new Foo object after assigning a new object to Foo.prototype its

问题 I have class named Novel . I can declare array of objects as mentioned below: Novel obj; but problem is Novel has constructor which I want to be called for all indexes of array how can I do that. I tried following but it does not work. Novel obj(i,n)[2]; 回答1: You need to use a proper container that uses dynamic allocation to defer construction of individual elements. std::vector<Novel> objs(2, Novel(i,n)); http://en.cppreference.com/w/cpp/container/vector/vector 回答2: Unfortunately the C++

问题 I have a class (let's name it TheClass ) that is quite often used in the following situation: several instances are constructed from constants and passed as several arguments to some other constructor. Unfortunately I have to use quite cumbersome syntax for the initialization: Otherclass{ TheClass{1, 'a', 2}, TheClass{1, 'b', 4}, TheClass{3, 'h', 2}, TheClass{1, 't', 8} } Is there a way to make it possible to initialize the class as if it was POD? I.e. I want to be able to write Otherclass{

问题 First of all this is not a duplicate question. I know the facts that: During inheritance, the order of execution of constructors will be in the same order as their derivation and order of execution of destructors will be in reverse order of their derivation. Also, we can call base class constructor explicitly using base keyword in constructor definition. My question is : For my below code class ClassA { public ClassA(int a) { Console.WriteLine("Parameterized Constructor of ClassA"); } } class

问题 I am trying to read a list of exercises from a file Exercises.txt in my /assests folder and I've found plenty of examples how to, but I keep getting the error "context cannot be resolved" and if I manage to fix that, then I get "Default constructor cannot handle exception type IOException thrown by implicit super constructor. Must define an explicit constructor" Here is my code: class ChooseExercises extends ListActivity{ String[] exercises; AssetManager am = context.getAssets(); //Error 1

问题 I'm trying to monkey patch a javascript Date constructor. I have the following code: var __Date = window.Date; window.Date = function(){ __Date.apply(this, Array.prototype.slice.call(arguments)); }; window.Date.prototype = __Date.prototype; As far as I know the javascript constructor (when called) does three things: It creates a new object that the this points to when the constructor function is executed It sets up this object to delegate to this constructor's prototype. It executes the

问题 I'm trying to figure out how to ask the user whether they want to replace the previous object of the same class with the default object, or simply use the previous object, when calling the constructor. I'm looking for actions in both these cases: >>obj = Obj() 'obj' already exists. Replace it with default? (y/n): y %clear obj and call default constructor to create new obj >>obj = Obj() 'obj' already exists. Replace it with default? (y/n): n %cancel call of Obj() How would I do this? I've

问题 According to Android developers website, " Every fragment must have an empty constructor, so it can be instantiated when restoring its activity's state". So in the new sample projects they have the fragment instantiation like following: public static class PlaceHolderFragment extends Fragment { public PlaceHolderFragment() {} ... } Is this necessary (encouraged?) for non-static fragment classes? Actually, I don't quite understand how the empty constructor will help restoring the activity

问题 i am getting error in this code class business { public: business(); // Default Constructor business(string busines,int r) { busines=busines; ratings=r; } // constructor; private: string busines; int ratings; int items_owned; int business_cancellation; int biz_size_of_building; int biz_shipping_method; }; int main(int argc, char *argv[]) { business b[10]; b[b_count](busines,rating); return 0; } It gives me the following error (http://ideone.com/FfajNS): prog.cpp: In function ‘int main(int,

问题 I just upgraded my PHP version from v5.3.1 to v5.3.9 . Suddenly class constructors started not working. Any ideas? 回答1: You are probably using constructors with Class name instead of __construct() keyword. See the behaviour change in v5.3.3 here: http://www.php.net/archive/2010.php#id2010-07-22-2 Use __construct() and you should be fine. http://www.php.net/manual/en/language.oop5.decon.php 来源： https://stackoverflow.com/questions/9094910/php-version-upgrade-caused-problems-with-class