I am not able to access a virtual property (IsNameAPalindrome) of an abstract class (PetBase ) having interface(IPet) inherited.
public interface IPet
{
string Name { get; set; }
}
public abstract class PetBase : IPet
{
public abstract string Name { get; set; }
public virtual bool IsNameAPalindrome
{
get
{
return (Name.Equals(string.Join("", Name.Reverse())));
}
}
}
The derived classes inherit the abstract class (PetBase)
public class Bird : PetBase
{
public override string Name { get; set; }
}
public class Cat : PetBase
{
public override string Name { get; set; }
}
public class Dog : PetBase
{
public override string Name { get; set; }
}
public class House : List<IPet>
{
}
Now when I try to access the property(IsNameAPalindrome) while looping through house object, it is not accessible
class Program
{
static void Main(string[] args)
{
House house = BuildHouse();
Print(house);
}
static void Print(House house)
{
// TODO: Print the contents of the house similar to the below.
// Feel free to change or improve upon the table as you see fit.
//Name Palindrome
//Gracie False
//Patches False
//Izzi True
//Missy False
Console.WriteLine("Name Palindrome");
foreach (var item in house)
{
Console.WriteLine( item.Name);
}
}
static House BuildHouse()
{
House house = new House();
house.Add(new Cat()
{
Name = "Gracie"
});
house.Add(new Cat()
{
Name = "Patches"
});
house.Add(new Bird()
{
Name = "Izzi"
});
house.Add(new Dog()
{
Name = "Missy"
});
return house;
}
}
You define House as List<IPet>, meaning the compiler will see each list element as the type IPet, which does not have a property IsNameAPalindrome.
If it makes logical sense for IsNameAPalindrome to be part of that interface contract, the simple solution is to add it:
public interface IPet
{
string Name { get; set; }
bool IsNameAPalindrome { get; }
}
If that does not make sense to you (and it may not, given that palendromes aren't closely linked to the concept of being a pet), you can:
Cast each IPet to PetBase to access that property
Implement a new interface e.g. IPalendrome, have PetBase also implement that interface, and cast to that interface to access the method.
Changes to the code for
First option
Console.WriteLine( ((PetBase)item).IsNameAPalindrome);
Second option
public interface IPalendrome
{
bool IsNameAPalindrome { get; }
}
public abstract class PetBase : IPet, IPalendrome
{
...
}
Console.WriteLine( ((IPalendrome)item).IsNameAPalindrome);
Related
I have a problem with C# generics, and I'm not sure about the most elegant solution. I've been programming a while but am new to the C# ecosystem so don't know common terminology for searching.
I'm trying to refactor code to reduce existing copy-paste duplication of classes. It is easy to resolve with one level of generics, but I can't get it working with two.
A very simplified example is below. The core issue is that BaseProfile cannot use any implementation details relating to DetailsA or DetailsB as it does not know the type. So UpdateDetailsId() has to be duplicated in 2 derived classes, instead of having a single Profile class handle it. Keep in mind this is a toy example just to express the relationships. The real classes have tens of fields, but a common subset which we are using in the class in question, so even if DetailsA and DetailsB look identical assume we need both.
public abstract class BaseProfile<TypeOfPerson>
{
public TypeOfPerson Person { get; set; }
}
public class Profile1 : BaseProfile<PersonA>
{
public void UpdateDetailsId(int id)
{
this.Person.Details.Id = id;
}
}
public class Profile2 : BaseProfile<PersonB>
{
public void UpdateDetailsId(int id)
{
this.Person.Details.Id = id;
}
}
public class PersonA
{
public DetailsA Details { get; set; }
}
public class PersonB
{
public DetailsB Details { get; set; }
}
public class DetailsA
{
public int Id { get; set; }
}
public class DetailsB
{
public int Id { get; set; }
}
I can add interfaces as it is referring to all the same fields for each type. However, C# will not allow an interface to include another interface and automatically resolve it in the implementation, because the member has to exactly match i.e. I thought I could just add IDetails Details to the IPerson interface but the fields now need to be type IDetails instead of DetailsA which implements IDetails. If I do that then I lose compiler type safety and can put the wrong Details on the wrong Person.
I have had success doing a public/private field pair like below, but this only validates and throws at runtime when casting value to DetailsA. I'd prefer something safer but I don't know if this is the best option. The goal of this example is a single Profile class, handling multiple Person classes, each with their own Details type that has an int Id field.
public class PersonA : IPerson
{
public IDetails Details
{
get { return _details; }
set { _details = (DetailsA)value; }
}
private DetailsA _details { get; set; }
}
One way of achieving this is by defining the type relationship between PersonA to DetailsA in a generic way, and specify a second generic type on BaseProfile.
Profile1 : BaseProfile<PersonA, DetailsA>
Consider the following code (note that I'm using Net6, so I have all these nullable reference type operators):
public abstract class BaseProfile<TPerson, TDetails>
where TDetails : IDetails, new()
where TPerson : PersonDetails<TDetails>, new()
{
public TPerson? Person { get; set; } = new TPerson();
public virtual void UpdateDetailsId(int id)
{
Person!.Details!.Id = id;
}
}
public class Profile1 : BaseProfile<PersonA, DetailsA>
{
}
public class Profile2 : BaseProfile<PersonB, DetailsB>
{
}
public abstract class PersonDetails<TDetails>
where TDetails : IDetails, new()
{
public virtual TDetails? Details { get; set; } = new TDetails();
}
public class PersonA : PersonDetails<DetailsA>
{
}
public class PersonB : PersonDetails<DetailsB>
{
}
public interface IDetails
{
int Id { get; set; }
}
public class DetailsA : IDetails
{
public int Id { get; set; }
public string? FirstName { get; set; }
}
public class DetailsB : IDetails
{
public int Id { get; set; }
public string? LastName { get; set; }
}
Testing with the following snippet
var profile1 = new Profile1();
var profile2 = new Profile2();
profile1.UpdateDetailsId(10);
profile2.UpdateDetailsId(12);
Console.WriteLine(profile1.Person!.Details!.Id);
Console.WriteLine(profile2.Person!.Details!.Id);
Console.WriteLine();
Update:
Because you included explicit casting in your snippet for Details property getters and setter, I also want to show a pattern using a concrete type inheriting on these generic types -- then demonstrate implicit/explicit operator user-defined conversion patterns.
Add the following declarations:
public abstract class BaseProfile<TPerson>
where TPerson : PersonDetails<GenericDetails>, new()
{
public TPerson? Person { get; set; } = new TPerson();
public virtual void UpdateDetailsId(int id)
{
Person!.Details!.Id = id;
}
public static explicit operator Profile1(BaseProfile<TPerson> details)
{
var profile = new Profile1();
profile.Person!.Details = (GenericDetails)details.Person!.Details!;
return profile;
}
public static explicit operator Profile2(BaseProfile<TPerson> details)
{
var profile = new Profile2();
profile.Person!.Details = (GenericDetails)details.Person!.Details!;
return profile;
}
}
public class GenericProfile : BaseProfile<GenericPerson>
{
}
public abstract class GenericPersonDetails : PersonDetails<GenericDetails>
{
}
public class GenericPerson : GenericPersonDetails
{
}
public class GenericDetails : IDetails
{
public int Id { get; set; }
public static implicit operator DetailsA(GenericDetails details)
{
return new DetailsA() { Id = details.Id };
}
public static implicit operator DetailsB(GenericDetails details)
{
return new DetailsB() { Id = details.Id };
}
}
and, update the testing functional scope:
var profile1 = new Profile1();
var profile2 = new Profile2();
var genericProfile = new GenericProfile();
profile1.UpdateDetailsId(10);
profile2.UpdateDetailsId(12);
genericProfile.UpdateDetailsId(20);
Console.WriteLine(profile1.Person!.Details!.Id);
Console.WriteLine(profile1.Person!.Details!.FirstName ?? "No First Name");
Console.WriteLine(profile2.Person!.Details!.Id);
Console.WriteLine(profile2.Person!.Details!.LastName ?? "No Last Name");
Console.WriteLine(genericProfile.Person!.Details!.Id);
Console.WriteLine(((Profile1)genericProfile).Person!.Details!.FirstName ?? "No First Name");
Console.WriteLine(((Profile2)genericProfile).Person!.Details!.LastName ?? "No Last Name");
Console.WriteLine();
I'm having trouble getting a class to inherit fields from its parent class.
I want the BullFrog class and Toad class to inherit all attributes from Amphibian class, and then overwrite the weight attribute. I thought it inherited all traits from the parent class by default, what am I missing here?
public class Animal
{
public string sound { get; set; }
public string move { get; set; }
public string favSnack { get; set; }
public double avgWeight { get; set; }
public void Speak(string sound)
{
Console.WriteLine( $"I go {sound}.");
}
public void Move(string move)
{
Console.WriteLine($"I {this.move} around the farm all day.");
}
public void Eat(string favSnack)
{
Console.WriteLine($"I like to eat {favSnack}.");
}
public void Weight(int avgWeight)
{
Console.WriteLine($"I usually weigh about {avgWeight}lbs.");
}
}
//decide on four or more animals
//for each animal decide on four or more methods
public class Amphibian : Animal
{
string sound = "ribbit";
string move = "hop";
string favSnack = "flies";
double avgWeight = .05d;
}
public class BullFrog : Amphibian
{
double avgWeight = .375d;
}
public class Toad : Amphibian
{
double avgWeight = .175d;
}
where did I go wrong? when I call the methods
BullFrog kermit = new BullFrog();
kermit.Move(kermit.movement);
kermit.Eat(kermit.favSnack);
I get "I around the farm all day" and two blank lines as the output.
My question is
Check the virtual and override keywords in C#. This is to be used in case you want to actually change the way the derived class moves. Go with the constructor way if it's just a string change.
public class Animal
{
public virtual string move { get; set; }
public class Amphibian : Animal
{
public override string move { get; set; } = "hop";
Your line string move = "hop"; is just declaring a private property inside the Amphibian class, which will not affect the base class in any way.
Another way to handle this would be to set the value in a constructor, but you should remember to always set the value in any constructor you are creating.
public class Animal
{
public string move { get; set; }
public Animal(string move) {
this.move = move;
}
And then
public class Amphibian : Animal
{
public Amphibian(): base("hop") {
}
Say I have the following classes:
public abstract class A
{
protected abstract ReturnA Foo();
public void UseFoo()
{
var foo = Foo();
if (foo != null)
{
//logic here
}
}
}
public class B : A
{
protected override ReturnA Foo()
{
// Implementation specific code that returns ReturnB instead.
}
}
public class C : A
{
protected override ReturnA Foo()
{
// Implementation specific code that returns ReturnC instead.
}
}
public class ReturnA
{
public int Id { get; set; }
public string Address { get; set; }
}
public class ReturnB
{
public string Id { get; set; }
public string PhoneNumber { get; set; }
}
public class ReturnC
{
public Guid Id { get; set; }
public string Name { get; set; }
}
I know that C# does not support derived return types, but this is not what I need either.
Classes B and C are implementation specific and therefore their return types have nothing to do with eachother.
The reason why I would want to handle this, is because the method UseFoo in class A may have some generic checks and other generic logic, that has nothing to do with the returned object itself.
So I want to "outsource" only the code that is implementation specific and not have to instead make UseFoo abstract and have every implementation write the same generic code.
Is there any way to solve this at all?
EDIT: Neither ReturnC nor ReturnB are derived from ReturnA. Updated with examples.
I am trying to access all the properties of my derived class through base class reference variable.
Classes
public class vehicle
{
public int ID { get; set; }
}
public class Car : vehicle
{
public string type { get; set; }
public string Name { get; set; }
}
Here is the main in Main class
public static void saveCar<T>(T vehicle) where T : vehicle
{
//TODO : here I need to access all the propertie values but I dunno how access only derived class values
}
I am trying to do this way
static void Main(string[] args)
{
Car cr = new Car
{
ID = 1,
type = "car",
Name = "Maruthi"
};
saveCar<Car>(cr);
}
You can't really ask for T and know your real properties.
I think you should change your design to something like this:
public abstract class Vehicle
{
public int Id { get; set; }
public virtual void SaveCar()
{
// save Id
}
}
public class Car : Vehicle
{
public string Type { get; set; }
public string Name { get; set; }
public override void SaveCar()
{
base.SaveCar();
// Save type & name
}
}
Why do you have saveCar as a generic method? If the saveCar method is a virtual method on Vehicle you can override and have the required extended save functionality in each derived type.
However if you require an external method to handle actions such as save and have Vehicle and its derived classes as simple data representations, you will need to inspect the object and act accordingly. Some like:
public static void saveCar(Vehicle vehicle)
{
if (vehicle != null)
{
Console.WriteLine(vehicle.ID);
if (vehicle is Car)
{
var car = vehicle as Car;
Console.WriteLine(car.Name);
}
}
}
I am fairly new to inheritance and wanted to ask something. I have a base class that has lots of functionality that is shared by a number of derived classes.
The only difference for each derived class is a single method called Name. The functionality is the same for each derived class, but there is a need for the Name distinction.
I have a property in the base class called Name. How do I arrange it so that the derived classes can each override the base class property?
Thanks.
Declare your method as virtual
public class A
{
public virtual string Name(string name)
{
return name;
}
}
public class B : A
{
public override string Name(string name)
{
return base.Name(name); // calling A's method
}
}
public class C : A
{
public override string Name(string name)
{
return "1+1";
}
}
Use a virtual property:
class Base
{
public virtual string Foo
{
get;
set;
}
}
class Derived : Base
{
public override string Foo
{
get {
// Return something else...
}
set {
// Do something else...
}
}
}
You can declare it with a virtual or abstract keyword in the base class, then the derived class can over-ride it
you need to declare your property (in the base clase) as virtual
To enable each derived class to override the property you just need to mark the property as virtual
class Base {
public virtual Property1 {
get { ... }
set { ... }
}
}
Well I'm not sure from your description that inheritance is actually the right solution to the problem but here's how you make it possible for a property to be overridden:
class Base
{
public virtual string Name { get; set; }
}
But do you need it to be writable? A readonly property may make more sense in which case this might work:
class Base
{
public virtual string Name
{
get { return "BaseName"; }
}
}
class Derived : Base
{
public override string Name
{
get { return "Derived"; }
}
}
In the base class:
public virtual string Name { get; set; }
In the derived classes:
public override string Name { get; set; }
However, if the only difference between the classes is that they have different names, I'd argue that instead of inheritance you should just use the base class with the Name set in the constructor:
e.g.
public class MyObject
{
public string Name { get; private set; }
public enum ObjectType { TypeA, TypeB, ... }
public MyObject(ObjectType obType)
{
switch (obType)
{
case ObjectType.TypeA:
Name = "Type A";
// and so on
}
}
}