constructor

问题 For a game I'm attempting to develop, I am writing a resource pool class in order to recycle objects without calling the "new" operator. I would like to be able to specify the size of the pool, and I would like it to be strongly typed. Because of these considerations, I think that a Vector would be my best choice. However, as Vector is a final class, I can't extend it. So, I figured I'd use composition instead of inheritance, in this case. The problem I'm seeing is this - I want to

问题 Basically what I am trying to achieve is to create a local (and private) instance of the class deltaKinematics in the class geneticAlgorithm In the geneticAlgorithm.h file I have: class DeltaKinematics; //class is defined in separate linked files class GeneticAlgorithm { //private DeltaKinematics deltaRobot; public: GeneticAlgorithm(); //constructor }; This is all fine, but when I go to declare the GeneticAlgorithm constructor, I can't work out how to construct the instance of DeltaKinematics

问题 Suppose I have an abstract base class Deck: public abstract class Deck { public List<Card> cards; public Deck(string[] values, string[] suits) {...} ... } and a derived class EuchreDeck: public class EuchreDeck : Deck { string[] values = new string[] { "9", "10", "J", "Q", "K", "A" }; string[] suits = new string[] { "clubs", "spades", "hearts", "diamonds" }; public EuchreDeck() : base(values, suits) // Error. {} ... } I want the ability to instantiate EuchreDeck and have the two string arrays

问题 I'm experiencing a weird behavior with GDB passing a string as the parameter to a constructor. The code works fine, but when I step through in the debugger, GDB seems to think my parameter is at a different address then it is. Does anyone know what's going on here? Here's the simplest program I can create that demonstrates the problem: --(jwcacces@neptune)--------------------------------------------(/home/jwcacces)-- --$ nl gdb_weird.cpp 1 #include <iostream> 2 #include <string> 3 4 class C 5

问题 Just wondering is it best to define an empty constructor or leave the constructor definition out completely in PHP? I have a habit of defining constructors with just return true; , even if I don't need the constructor to do anything - just for completion reasons. 回答1: If you don't need a constructor it's best to leave it out, no need to write more code. When you DO write it, leave it empty... returning true doesn't have a purpose. 回答2: There is a difference between the two: If you write an

问题 Will the initialization list always be processed before the constructor code? In other words, will the following code always print <unknown> , and the constructed class will have "known" as value for source_ (if the global variable something is true )? class Foo { std::string source_; public: Foo() : source_("<unknown>") { std::cout << source_ << std::endl; if(something){ source_ = "known"; } } }; 回答1: Yes, it will, as per C++11: 12.6.2 /10 (same section in C++14 , 15.6.2 /13 in C++17 ): In a

问题 I know that it is not a good practice to call a method in the constructor of a class in C# but I stuck on something strange. My problem is that when I create an object of my class I need to assign a field in my object with a random number. for instance class RandomNumberHandler { private int randomNumber; public RandomNumberHandler() { this.randomNumber = GenerateRandomNumber(); } private int GenerateRandomNumber() { return (new Random()).Next(3000) + 1000; } } In my case I need a four digit

问题 I'm trying to implement the singleton pattern in a database helper class, but, I can't seem to understand the purpose of a factory constructor and if there's an alternative method to using it. class DbHelper { final String tblName =''; final String clmnName =''; final String clmnPass=''; DbHelper._constr(); static final DbHelper _db = new DbHelper._constr(); factory DbHelper(){ return _db;} Database _mydb; Future<Database> get mydb async{ initDb() { if(_mydb != null) { return _mydb; } _mydb =

问题 I have a problem with Cython usage of default constructors. My C++ class Node is the following Node.h class Node { public: Node() { std::cerr << "calling no arg constructor" << std::endl; w=0.0; d=0.0; } Node(double val, double val2); { std::cerr << "calling 2 args constructor" << std::endl; this->w=val; this->d=val2; } private: double d,w; } is wrapped in Cython as follows cdef extern from "Node.h": cdef cppclass Node: Node() except + Node(double val1, double val2) except + double d double w

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 years ago . The oops rule is "No class can exist without constructor".its ok.But in java Anonymous class can'never have its constructor.because it does not have any name. So it is contradict OOPS rule..I m really confused.Is it breaking OOPS rule?Please help 回答1: Actually, they have one implicit constructor. Suppose you