constructor

问题 I can't understand the advantages of or differences between vector copy constructors and range constructors. When I construct three vectors like this: vector<int> FirstVec(3, 911); //fill constructor vector<int> SecondVec(FirstVec.begin(), FirstVec.end()); //range constructor vector<int> ThirdVec(FirstVec); //copy constructor The contents of SecondVec and ThirdVec are exactly the same. Are there any scenarios in which using one of them has advantages? Thank you. 回答1: The range constructor is

问题 The following code fails with gcc 4.8.0 (mingw-w64) with -O2 -std=c++11 -frtti -fexceptions -mthreads #include <string> class Param { public: Param() : data(new std::string) { } Param(const std::string & other) : data(new std::string(other)) { } Param(const Param & other) : data(new std::string(*other.data)) { } Param & operator=(const Param & other) { *data = *other.data; return *this; } ~Param() { delete data; } Param & operator=(Param &&) = delete; private: std::string * data; }; int main(

问题 What's the best way to handle exceptions that happen from within a controller's constructor? All I can think of to do is use Application_OnError() or put a try/catch in my ControllerFactory. Neither of these solutions seem ideal. Application_OnError is to broad - I have some non-mvc content in the site that has its own error handling. Using a try/catch block seems kinda hacky. If I'm serving different content type -html/text/json/rss.... I would like to be able to handle the exception from

问题 What's the best way to handle exceptions that happen from within a controller's constructor? All I can think of to do is use Application_OnError() or put a try/catch in my ControllerFactory. Neither of these solutions seem ideal. Application_OnError is to broad - I have some non-mvc content in the site that has its own error handling. Using a try/catch block seems kinda hacky. If I'm serving different content type -html/text/json/rss.... I would like to be able to handle the exception from

问题 For example, we have this parent: open class Parent(val id: Int, val name: String?) { constructor() : this(-1, null) } And a child, which must have both a two-param constructor and an empty constructor, like the parent: class Child(id: Int, name: String?) : Parent(id, name) { constructor() : super() // syntax error } How can a child constructor use its parent's secondary constructor? I am aware that I can implement a child constructor passing in the same values as the parent, but this not

问题 The following is the C++ source code. The code has a class HumanBeing and with Display and verify functions. Each function prints statements. #include <iostream> using namespace std; class HumanBeing { public: void display() { cout << "hello aam a human being" << endl; } void print() { cout << "verify print" << endl; } }; int main() { HumanBeing vamshi; vamshi.display(); vamshi.print(); return 0; } This is the corresponding assembly code of the above c++ code .file "verify.cpp" .local _ZStL8_

问题 I know interfaces cannot define constructors. What is the best practice to force all classes implementing an interface, to receive their dependencies in a uniform contract. I know ints possible to inject dependencies into objects via properties, but passing them via constructors makes more sense to me. How to DI then ? 回答1: I know you said you want to have a stable contract. But an advantage to not supplying a stable interface is that your dependencies could then vary wildly with different

问题 If I have a function like this: function a() { console.log('a'); } and then assign a static property like this: a.static = 'foo'; But say I want to override the function with another function like this: var old = a; a = function() { console.log('new'); old.call(this); }; a.static // undefined Since I assigned a new function to a , it’s static properties are lost. Is there a neat way to keep the static properties without looping and manually copying them? Update: Here’s a real world scenario:

问题 The specific use where I thought of this problem is as follows, but it's much more generalized. I have a custom JFrame class which also serves as an ActionListener for its components. So my constructor looks something like the following: private JButton myButton; public MyCustomFrame() { super(); myButton.addActionListener(this); // ... more stuff } My question is, how does this actually work behind the scenes? If the constructor is what "creates" the object which is referenced by this , how

问题 The specific use where I thought of this problem is as follows, but it's much more generalized. I have a custom JFrame class which also serves as an ActionListener for its components. So my constructor looks something like the following: private JButton myButton; public MyCustomFrame() { super(); myButton.addActionListener(this); // ... more stuff } My question is, how does this actually work behind the scenes? If the constructor is what "creates" the object which is referenced by this , how