inheritance

问题 This question helped me to understand a bit, but my question is slightly different from theirs. Basic typecasting as I understand it in c++ involves reinterpreting a structure in memory, as a different structure. For example: class Building{int sqFootage;}; class Office : public Building{int cubicles;}; int main(int argc, char** argv){ Office *foo = new Office(); /*The cubicles member appears after the sqFootage member on an Office, * so the foo pointer is really just a Building* with some

问题 My base class: class Item { protected: int count; string model_name; int item_number; public: Item(); void input(); } My derived Class: class Bed : public Item { private: string frame; string frameColour; string mattress; public: Bed(); void input(); } for now all my input function is trying to do is output which method is being used: void Item::input() { cout<<"Item input"<<endl; } void Bed::input() { cout<<" Bed Input"<<endl; } when I call the function in main I'd like the derived class

问题 This question already has answers here : Java : recursive constructor call and stackoverflow error (5 answers) Closed 2 years ago . My Superclass is: public abstract class MarketProduct { private String name; public MarketProduct(String productName) { name = productName; } public final String getName() { return this.name; } public abstract int getCost(); public abstract boolean equals(Object o); } And my subclass (up until its constructor) is: public class Egg extends MarketProduct { private

问题 If I have two classes, A and B, public class A { public int test() { return 1; } } public class B extends A{ public int test() { return 2; } } If I do: A a1 = new B() , then a1.test() returns 2 instead of 1 as desired. Is this just a quirk of Java, or is there some reason for this behavior? 回答1: No, that is correct (it is due to polymorphism). All method calls operate on object, not reference type. Here your object is of type B, so test method of class B will be called. 回答2: This is called

问题 If I have two classes, A and B, public class A { public int test() { return 1; } } public class B extends A{ public int test() { return 2; } } If I do: A a1 = new B() , then a1.test() returns 2 instead of 1 as desired. Is this just a quirk of Java, or is there some reason for this behavior? 回答1: No, that is correct (it is due to polymorphism). All method calls operate on object, not reference type. Here your object is of type B, so test method of class B will be called. 回答2: This is called

问题 Consider the following javascript code var a = Object.create(null); a.foo = 1; var b = Object.create(a); console.log(b.foo); //prints 1 console.log(b.__proto__); //prints undefined b.__proto__ = null; console.log(b.__proto__); //prints null console.log(b.foo); //prints 1 Can anyone explain how object b is accessing the "foo" property of a even after setting b.__proto__ to null? What is the internal link which is used to access the property of a ? I tried searching through SO for possible

问题 I'm confused as to why the C++ compiler won't accept this: class Foo { private: void Baz() { } }; class Bar { public: void Baz() { }; class FooBar : public Foo, public Bar { }; void main() { FooBar fb; fb.Baz(); } The error gcc gives is: request for member ‘Baz’ is ambiguous candidates are: void Bar::Baz() void Foo::Baz() but isn't it obvious that I want Bar::Baz(), since Foo::Baz() is private? Why won't the compiler disambiguate here? 回答1: Name resolution works in two stages. First the name

问题 I'm trying to give a model to the shared layout so the menu links are created dynamically from a database. Any ideas where I should start? I am looking for maybe tutorials of how to use inheritance to do this? 回答1: You could do this: Model public partial class Menu { public String[] items; public Menu(String[] items) { this.items = items; } } View (_Menu) @model YourMVC.Models.Menu <ul> @foreach (String item in Model.items) { <li>@item</li> } </ul> Place this in _Layout @Html.Action("_Menu",

问题 I'm trying to give a model to the shared layout so the menu links are created dynamically from a database. Any ideas where I should start? I am looking for maybe tutorials of how to use inheritance to do this? 回答1: You could do this: Model public partial class Menu { public String[] items; public Menu(String[] items) { this.items = items; } } View (_Menu) @model YourMVC.Models.Menu <ul> @foreach (String item in Model.items) { <li>@item</li> } </ul> Place this in _Layout @Html.Action("_Menu",

问题 I'm trying to give a model to the shared layout so the menu links are created dynamically from a database. Any ideas where I should start? I am looking for maybe tutorials of how to use inheritance to do this? 回答1: You could do this: Model public partial class Menu { public String[] items; public Menu(String[] items) { this.items = items; } } View (_Menu) @model YourMVC.Models.Menu <ul> @foreach (String item in Model.items) { <li>@item</li> } </ul> Place this in _Layout @Html.Action("_Menu",