Generic Lookup Method
I'm wanting to create a generic lookup method to where you specify a type of object and some other identifying parameters and the method returns an object of that type. Is this 开发者_Python百科possible?
I'm thinking something like this.
public T GetObjectOfType(Guid ID, typeof(T Class))
{
//lookup this object and return it as type safe
}
I know this just won't work but i hope it explains the concept
You can use a generic method for this:
public T GetObjectOfType<T>(Guid id) where T: class, new()
{
if (id == FooGuid) //some known identifier
{
T t= new T(); //create new or look up existing object here
//set some other properties based on id?
return t;
}
return null;
}
If all you want is create an instance of a specific type you do not need the additional id parameter, I assume you want to set some properties etc. based on the id. Also your class must provide a default constructor, hence the new()
constraint.
Typically factory methods do not take the type of object to create. They return a type that implements some common interface and the concrete, underlying type is dependent on some argument, typically an enumerated value. A simple example:
interface Whatever
{
void SomeMethod();
}
class A : Whatever { public void Whatever() { } }
class B : Whatever { public void Whatever() { } }
enum WhateverType { TypeA, TypeB }
public void GetWhatever( WhateverType type )
{
switch( type )
{
case WhateverType.TypeA:
return new A();
break;
case WhateverType.TypeB:
return new B();
break;
default:
Debug.Assert( false );
}
}
There you have type safety. I'm not sure how you would implement something like that with generics as you need to supply the generic argument at compile time.
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