I've run my code through code coverage and the line below shows 1 block as not covered.
Can anyone tell me which part of that line isn't executing?
An Example to play with:
public abstract class Base
{
public abstract IExample CreateEntity<TExample>() where TExample : IExample, new();
}
public class Class1 : Base
{
public override IExample CreateEntity<TExample>()
{
IExample temp = new TExample();
return temp;
}
}
public interface IExample
{
}
public class TEx : IExample
{
}
and the test method
[TestMethod]
public void TestMethod1()
{
Class1 ex = new Class1();
ex.CreateEntity<TEx>();
}
A generic type is like a template. You cannot create instances of it unless you specify real types for its generic type parameters. To do this at run time, using reflection, requires the MakeGenericType method.
The short answer is, that there is no way to find out the runtime type of generic type parameters in Java. A solution to this is to pass the Class of the type parameter into the constructor of the generic type, e.g.
Like C++, we use <> to specify parameter types in generic class creation. To create objects of a generic class, we use the following syntax. Note: In Parameter type we can not use primitives like 'int','char' or 'double'.
A Generic Version of the Box Class To update the Box class to use generics, you create a generic type declaration by changing the code "public class Box" to "public class Box<T>". This introduces the type variable, T, that can be used anywhere inside the class.
Change your constraint to force the TExample
to be a class:
public abstract IExample CreateEntity<TExample>() where TExample : class, IExample, new();
If you run your compiled code through a tool like ILSpy, you will see the block that is not getting coverage:
TExample temp = (default(TExample) == null) ? Activator.CreateInstance<TExample>() : default(TExample);
return temp;
It is performing a check to see if the type passed to the generic was a reference type or a value type. By forcing it to be a class, this check will be removed. Read more on the default keyword here: http://msdn.microsoft.com/en-us/library/xwth0h0d.aspx
Another way to get complete code coverage would be to use a struct that implements IExample
:
public struct S1 : IExample
{
}
And then add this test:
[TestMethod]
public void StructTest()
{
Class1 ex = new Class1();
ex.CreateEntity<S1>();
}
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