upcasting

Cant copy construction be done without creating an explicit function in the pure virtual base class?

由 和自甴很熟 提交于 2019-12-22 18:32:36
问题 My objective is to do a deep copy of a class, but a virtual class is causing trouble. #include<iostream> using namespace std; class Vir//pure virtual class { public: virtual void hi()=0; }; class Handler:public Vir { public: int i; Handler() {} Handler(int val):i(val) {} void hi() {cout<<"Value of i="<<i<<endl;} int getI() const {return i;} void setI(int j) {i=j;} }; class ControlPanel { public: Vir *v; ControlPanel(const ControlPanel& c)//copy constructor { v=new Handler; v->setI(c.getI());

Does SFINAE apply to function bodies?

由 帅比萌擦擦* 提交于 2019-12-18 08:58:35
问题 I have the following sample code: class Serializable {}; class MyData : public Serializable {}; void GetData( Serializable& ) {} template<typename T> void GetData( T& data ) { std::istringstream s{"test"}; s >> data; } int main() { MyData d; GetData(d); } (Live Sample) Based on overload resolution rules, the non-template version should be preferred because the base class is of type Serializable . However, I expect SFINAE to kick in when there are errors in the template version when it is

How expensive is downcasting in Java 6? [closed]

由 爷，独闯天下 提交于 2019-12-18 07:08:59
问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 6 years ago . There is a method which receives an argument of type Collection and it needs to use some of the methods that are found in the List class when it does work with that argument. Is up-casting expensive in terms of speed? List<Stuff> list = (List<Stuff>) collection; I would also like

Upcasting the downcasted object back in protobuffers

由 天涯浪子 提交于 2019-12-13 21:24:08
问题 Below is the proto code, message Animal { optional string name = 1; optional int32 age = 2; } message Dog{ optional string breed = 1; } Then the sample class using the above proto public class InheritanceTest { public static void main(String[] args){ Dog dog = Dog.getDefaultInstance(); printAnimalName(dog.getAnimal()); } public static void printAnimal(Animal animal){ Dog dog = (Dog)animal; // Not at all possible right! } } Is up-casting possible only by having an instance of dog as "required"

String to Object typecasting - Difference

由 回眸只為那壹抹淺笑 提交于 2019-12-11 04:48:52
问题 What is the difference between. public class Test { public static void main(String args[]) { String toBeCast = "cast this string"; A a = toBeCast; // error - Type mismatch: cannot convert from String to A Object object = toBeCast; } } public class A { } When we say every object extends Object class , why does A a = toBeCast; not allowed, but this Object object = toBeCast; works fine. 回答1: Remember that old saying from geometry class - "Every square is a rectangle, but not every rectangle is a

up-casting in C# and call a specific method based on the derived type

由 无人久伴 提交于 2019-12-09 03:14:54
问题 I have a couple of classes, all derived from the same base type. class basetype{} class TypeA : basetype{} class TypeB : basetype{} ... A number of them is stored in a list. List<basetype> myObjects As always, each of these types has to be handled differently. Now I have a couple of methods to handle them, and one method that takes the basetype as parameter. HandleTypes(TypeA obj){} HandleTypes(TypeB obj){} HandleTypes(basetype obj) currently, my HandleAllTypes looks like that: string name =

PHP upcasting object [duplicate]

由 a 夏天 提交于 2019-12-08 08:39:09
问题 This question already has answers here : Cast the current object ($this) to a descendent class (5 answers) Closed 5 years ago . can I upcast an object to it's parent object? Example Code class ClassA { public function foo(){ echo get_class($this); } } class ClassB extends ClassA { public function foo(){ echo get_class($this); // prints ClassB :) parent::foo(); // prints ClassB / I want ClassA :( } } $B = new ClassB(); $B->foo(); is it possible in PHP; In my scenario I'm building ClassB and I

memory allocation for upcasting in java

由 不打扰是莪最后的温柔 提交于 2019-12-07 14:24:57
问题 Considering these classes: public class Animal{ } public class Dog extends Animal{ } public AnimalTest(){ public static void main(String[] args){ Dog d = new Dog(); Animal a = d; } } my question is since I performed an upcasting on Animal a = d; does it consume a new memory allocation on the machine or does it use the memory allocated to the Dog d = new Dog(); 回答1: Animal a = d; a is just a reference and the reference's memory is allocated in method stack(or jvm stack, not heap). That is when

Cant copy construction be done without creating an explicit function in the pure virtual base class?

由 落爺英雄遲暮 提交于 2019-12-06 09:22:31
My objective is to do a deep copy of a class, but a virtual class is causing trouble. #include<iostream> using namespace std; class Vir//pure virtual class { public: virtual void hi()=0; }; class Handler:public Vir { public: int i; Handler() {} Handler(int val):i(val) {} void hi() {cout<<"Value of i="<<i<<endl;} int getI() const {return i;} void setI(int j) {i=j;} }; class ControlPanel { public: Vir *v; ControlPanel(const ControlPanel& c)//copy constructor { v=new Handler; v->setI(c.getI()); } int getI()const {return v->getI();} void initialize() {v=new Handler(10);} void hi() {v->hi();}

memory allocation for upcasting in java

由 霸气de小男生 提交于 2019-12-05 22:30:40
Considering these classes: public class Animal{ } public class Dog extends Animal{ } public AnimalTest(){ public static void main(String[] args){ Dog d = new Dog(); Animal a = d; } } my question is since I performed an upcasting on Animal a = d; does it consume a new memory allocation on the machine or does it use the memory allocated to the Dog d = new Dog(); Animal a = d; a is just a reference and the reference's memory is allocated in method stack(or jvm stack, not heap). That is when invoke the method main , JVM will allocate a stack which contains the reference's space. The Actual object
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