inheritance

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 . I will be grateful if someone can point out where the error is occurring. class hotel extends WishDBxyz{ public nomhotel; protected idhotel, ile_idile, pays_idpays, chainehotel_idchainehotel, actif ; } Just on second line got the error Parse error: syntax error, unexpected (T_STRING), expecting variable (T

问题 I have an upper class that has a var title and then I have different classes, that extend this upper one, in which I want to override that var title . I was trying with @override void set method, but I didn't understand how to use it properly. Can someone help me please? 回答1: You can use getter and setter combined with super to achieve the desired result: class Foo { String title; } class Override extends Foo { String get title { print("get title"); return super.title; } set title(value) {

问题 Let's say I want my method to accept anything that is "number like" i.e. knows how to negate, add, subtract, multiply and divide. It needs to do these with itself and with numbers (Int32 and Float64 for my purposes) abstract struct Numberlike alias Num = (Int32 | Float64) abstract def - abstract def +(other : self) abstract def +(other : Num) abstract def -(other : self) abstract def -(other : Num) abstract def *(other : self) abstract def *(other : Num) abstract def /(other : self) abstract

问题 I'm trying to understand whether the answer to the following question is the same in all major OOP languages; and if not, then how do those languages differ. Suppose I have class A that defines methods act and jump ; method act calls method jump . A 's subclass B overrides method jump (i.e., the appropriate syntax is used to ensure that whenever jump is called, the implementation in class B is used). I have object b of class B . I want it to behave exactly as if it was of class A . In other

问题 Excuse my terminology if it's off. I don't understand the difference between: function Person() {}; Person.walk = function() {}; and... function Person() {}; Person.prototype.walk = function() {}; It seems that the second way is the convention for constructors, but I don't understand the difference and why it is done that way. Thanks! 回答1: In the first case: function Person() {}; Person.walk = function() {}; You will be able to call the function only with: Person.walk(); If you create an

问题 When you model inheritance through class table inheritance relationships in a database model, do you... 1) Include an attribute (boolean for two subtipes, string for more subtipes) which identifies the particular subtipe of each record? 2) Include this identification as a foreign key to a table containing a description of all the possible subtypes? 3) None of the above and rely on "trial and error" lookup in subtables on the few times it is needed? 回答1: I would prefer in most cases the table

问题 I have a class A which has to have a a class passed to it; From A I have two classes B and C; is it possible for B and C to use the constructor from A, as apposed to the default constructor. A / \ B C A::A(randomNumber &rnd) { .... } 回答1: Yes, it is possible: class B { public: B(randomNumber& rnd) : A(rnd) { } // ... }; If you want to call A 's constructor in B 's default constructor, you will have to pass a global object: since A 's construct accepts an lvalue reference, creating a temporary

问题 I am experiencing some annoying behavior with Visual Studio .NET 2008. We have created a base form, and a base grid derived from Infragistics UltraGrid. In the base form, we have set some properties like colors, font size, etc. 1. We create a new Windows Form, (i.e. DerivedForm) 2. We change the inheritance to BaseForm, by simply adding a using statement and changing the inheritance in the class definition. 3. The IDE at this point copies all of the property settings you would see in BaseForm

问题 I need to derive a class from ComboBox and change its Items property. Here is my code: public class MyComboBox2 : ComboBox { private MyObjectCollection MyItems; public MyComboBox2() { MyItems = new MyObjectCollection(this); } //new public ComboBox.ObjectCollection Items new public MyObjectCollection Items { get { return MyItems; } } } public class MyObjectCollection : ComboBox.ObjectCollection { public MyObjectCollection(ComboBox Owner) : base(Owner) { } new public int Add(Object j) { base

问题 I have a custom class which I am extending for various purposes, and the following code is working just fine: class Inator { constructor(whichCanvas) { this.myCanvas = whichCanvas; } } class Ballgowninator extends Inator { constructor(whichCanvas) { super(whichCanvas); this.myCanvas.addEventListener("mousedown",this.handleMouseDown); this.myCanvas.addEventListener("mouseup",this.handleMouseUp); } handleMouseDown(e) { alert("ballgowninator mousedown"); } handleMouseUp(e) { alert(