polymorphism

问题 I'm making a game in pygame and I have made an 'abstract' class that's sole job is to store the sprites for a given level (with the intent of having these level objects in a list to facilitate the player being moved from one level to another) Alright, so to the question. If I can do the equivalent of this in Python(code curtesy of Java): Object object = new Object (){ public void overriddenFunction(){ //new functionality }; }; Than when I build the levels in the game I would simply have to

问题 I'm making a game in pygame and I have made an 'abstract' class that's sole job is to store the sprites for a given level (with the intent of having these level objects in a list to facilitate the player being moved from one level to another) Alright, so to the question. If I can do the equivalent of this in Python(code curtesy of Java): Object object = new Object (){ public void overriddenFunction(){ //new functionality }; }; Than when I build the levels in the game I would simply have to

问题 I'm making a game in pygame and I have made an 'abstract' class that's sole job is to store the sprites for a given level (with the intent of having these level objects in a list to facilitate the player being moved from one level to another) Alright, so to the question. If I can do the equivalent of this in Python(code curtesy of Java): Object object = new Object (){ public void overriddenFunction(){ //new functionality }; }; Than when I build the levels in the game I would simply have to

问题 I have a polymorphic relationship, comments: (id, text, commentable_id, commentable_type ), images :(id, title) and videos :(id, title). videos table has a many to many relationship with matters table. I managed to recover the comments and their relationship such as the video but I cannot recover the title of the matter, passing from the comments table, after the videos table and then table of matters. below my request. class Comment extends Model { public function commentable() { return

问题 I have a base class Object : struct Object{ }; and n (in this case 2) classes that inherit from this struct Integer : public Object{ int i_; Integer(int i) : i_{i}{} } struct Float : public Object{ float f_; Float(float f) : f_{f}{} } By (ab-)using polymorphism I can now store those two types in a vector: std::vector<Object*> object_list{new Integer(1), new Float(2.1), new Integer(3), new Float(4.2)}; But now I would like to add all those values together. I can think of... 1) ...defining

问题 class X { protected int v = 0; public X() { v += 10; } public void proc(X p) { System.out.println(43); } } class Y extends X { public Y() { v += 5; } public void proc(X p) { System.out.println(57); } public int getV() { return v; } } class Z extends Y { public Z() { v += 9; } public void proc(Z p) { System.out.println(39); } } class Main { public static void main(String[] args) { X x = new Z(); Y y = new Z(); Z z = new Z(); x.proc(z);// 1 System.out.println(y.getV()); } } From what I can

问题 I have this polymorphic code (see this question) with generic monads for model and client: import Control.Monad.Writer class Monad m => Model m where act :: Client c => String -> c a -> m a class Monad c => Client c where addServer :: String -> c () scenario1 :: forall c m. (Client c, Model m) => m () scenario1 = do act "Alice" $ addServer @c "https://example.com" and this is the pretty-print interpreter for the Client that explains the actions in the log via Writer monad: type Printer =

问题 I have this polymorphic code (see this question) with generic monads for model and client: import Control.Monad.Writer class Monad m => Model m where act :: Client c => String -> c a -> m a class Monad c => Client c where addServer :: String -> c () scenario1 :: forall c m. (Client c, Model m) => m () scenario1 = do act "Alice" $ addServer @c "https://example.com" and this is the pretty-print interpreter for the Client that explains the actions in the log via Writer monad: type Printer =

问题 I am kinda repeating this question bit the 1st time it was asked incorrectly. I have this: <xsd:complexType name="A"> <xsd:sequence> <xsd:element name="options" type="options"/> </xsd:sequence> </xsd:complexType> <xsd:complexType name="B"> <xsd:complexContent> <xsd:element name="options" type="ex_options"/> </xsd:complexContent> </xsd:complexType> <xsd:complexType name="options"> <xsd:sequence> ...some options </xsd:sequence> </xsd:element> <xsd:complexType name="ex_options"> <xsd

问题 I want to have a derived class which has a default constructor that initializes the inheirited members. Why can I do this class base{ protected: int data; }; class derived: public base{ public: derived(){ //note data = 42; } }; int main(){ derived d(); } But not this class base{ protected: int data; }; class derived: public base{ public: derived(): //note data(42){} }; int main(){ derived d(); } error: class ‘derived’ does not have any field named ‘data’ 回答1: An object can only be initialized