Is there any way to specify the return type for PexChoose at runtime? For example PexChoose.Value(name, Type)?
This would be useful to make general models that generate values of different types depending on runtime contraints.
You could build your own helper class which will call the generic version via reflection.
For instance, to create a non-generic version of PexChoose.Value(string name)
public static class MyPexChoose
{
public static object Value(Type myType, string name)
{
// Find the PexChoose.Value() method which has a single string parameter
MethodInfo method = typeof(PexChoose).GetMethod("Value", new Type[1] {typeof(string)});
// Make and invoke the generic version of it
MethodInfo generic = method.MakeGenericMethod(myType);
return generic.Invoke(typeof(PexChoose), new object[1] { name });
}
}
Then the call
MyPexChoose(typeof(DateTime), "MyChosen");
is equivalent to
PexChoose<DateTime>("MyChosen");
Related
In Objects in Kotlin: Create safe singletons in one line of code (KAD 27) Antonio Leiva states:
In fact, an object is just a data type with a single implementation.
I would expect to see the term instance rather than implementation used here. Is there some nuance that I am missing?
Sure it does have a single instance after all, but I believe what they meant to say is that whatever you write in an object is final and you can not override it. Even if you make it open(for argument purpose), you can not make an anonymous object out of it since the anonymous class can't be used on a SingleTon instance.
So " data type with a single implementation" means, whatever you write is the final implementation. An instance is, after all, a result of some implementation.
For reference, I am adding a decompiled code of object declaration.
public final class Test {
#NotNull
private static final String testMember = "Test";
public static final Test INSTANCE;
#NotNull
public final String getTestMember() {
return testMember;
}
private Test() {
}
static {
Test var0 = new Test();
INSTANCE = var0;
testMember = "Test";
}
}
I am attempting to create an instance of FileHelperEngine<> using a generic type. For example this works for List
public static IList CreateList(Type type)
{
var genericListType = typeof(List<>).MakeGenericType(type);
return (IList)Activator.CreateInstance(genericListType);
}
Is it possible to do something similar for FileHelperEngine<>?
I tried
public static FileHelperEngine CreateFileHelperEngine(Type type)
{
var genericFileHelperEngineType = typeof (FileHelperEngine<>).MakeGenericType(type);
return (FileHelperEngine)Activator.CreateInstance(genericFileHelperEngineType);
}
And get this error
Unable to cast object of type 'FileHelpers.FileHelperEngine`1[NachaParser.Model.EntryDetail.PpdEntryModel]' to type 'FileHelpers.FileHelperEngine'.
This would not work because you are attempting to go from the generic engine to the standard engine. The generic engine does not inherit from the standard engine so you can't directly cast.
The following code should work for you:
public static FileHelperEngine<T> CreateFileHelperEngine<T>() where T : class
{
var genericFileHelperEngineType = typeof(FileHelperEngine<>).MakeGenericType(typeof(T));
return (FileHelperEngine<T>)Activator.CreateInstance(genericFileHelperEngineType);
}
The problem is that you need to have the type of T not as a Type variable but as as a passed generic argument. Unfortunately, the generic engine is based of EngineBase<T> with IFileHelperEngine<T> as an interface it implements so you can never get a FileHelperEngine<T> to a FileHelperEngine.
Your only other option is to use:
public static FileHelperEngine CreateFileHelperEngine(Type type)
{
if (!type.IsClass)
throw new InvalidCastException("Cannot use '" + type.FullName + "' as it is not a class");
return new FileHelperEngine(type);
}
I have a repository offering a GetAll method which again calls the Query extension method on the ISession instance of NHibernate.
public ICollection<Product> GetAll()
{
return _session.Query<Product>().ToList();
}
My unit test looks like this:
[Test]
public void GetAllReturnsCollectionFromSession()
{
IQueryable<Product> productList = new ProductListBuilder().Build().AsQueryable();
_fixture.Session.Query<Product>().Returns(productList);
var sut = _fixture.CreateSut();
var result = sut.GetAll();
Assert.AreSame(productList, result);
_fixture.Session.Received().Query<Product>();
}
In the _fixture.Session.Query().Returns(productList) statement, NSubstitute throws the following exception:
NSubstitute.Exceptions.CouldNotSetReturnDueToTypeMismatchException : Can not return value of type IQueryable`1Proxy for ISession.GetSessionImplementation (expected type ISessionImplementor).
Make sure you called Returns() after calling your substitute (for example: mySub.SomeMethod().Returns(value)),
and that you are not configuring other substitutes within Returns() (for example, avoid this: mySub.SomeMethod().Returns(ConfigOtherSub())).
If you substituted for a class rather than an interface, check that the call to your substitute was on a virtual/abstract member.
Return values cannot be configured for non-virtual/non-abstract members.
Correct use:
mySub.SomeMethod().Returns(returnValue);
Potentially problematic use:
mySub.SomeMethod().Returns(ConfigOtherSub());
Instead try:
var returnValue = ConfigOtherSub();
mySub.SomeMethod().Returns(returnValue);
at NSubstitute.Core.ConfigureCall.CheckResultIsCompatibleWithCall(IReturn valueToReturn, ICallSpecification spec)
at NSubstitute.Core.ConfigureCall.SetResultForLastCall(IReturn valueToReturn, MatchArgs matchArgs)
at NSubstitute.Core.CallRouter.LastCallShouldReturn(IReturn returnValue, MatchArgs matchArgs)
at NSubstitute.Core.SubstitutionContext.LastCallShouldReturn(IReturn value, MatchArgs matchArgs)
at NSubstitute.SubstituteExtensions.Returns[T](MatchArgs matchArgs, T returnThis, T[] returnThese)
at NSubstitute.SubstituteExtensions.ReturnsForAnyArgs[T](T value, T returnThis, T[] returnThese)
at Statoil.Wellcom.DataLayer.Implementation.Oracle.UnitTests.Repositories.DwapplicationRepositoryTests.GetAllReturnsCollectionFromSession() in C:\git\WELLCOM\source\Statoil.Wellcom.DataLayer.Implementation.Oracle.UnitTests\Repositories\DwapplicationRepositoryTests.cs:line 123
It looks like NSubstitute is unable to set the return value due to Query being an extension method. How would I go about mocking the extension method call on the ISession?
The easiest solution is to wrap your ISession in another interface/concrete class so you can stub that out:
public interface ISessionWrapper
{
IQueryable<T> Query<T>();
}
public class SessionWrapper : ISessionWrapper
{
private readonly ISession _session;
public SessionWrapper(ISession session)
{
_session = session;
}
public IQueryable<T> Query<T>()
{
return _session.Query<T>();
}
}
There is no way to mock extension method with NSubstitute, however if you know what extension method is using inside, than you can mock that. Your test will use extension method on mocked object and eventually it will use mocked method. Difficult part is to know what is going on inside.
It worked for me in projects, where I knew all the source code and I could check what's inside.
I have at least two different classes like following :
//NOTE : these two classes have getter and setter also
class Artist {
String artistName;
String artistWebsite;
String artistDbpedia;
String artistImage;
List<String> astistAlbumsName;
List<String> astistAlbumsUrl;
}
class Venu {
String VenuName;
String VenuWebsite;
String VenuDbpdia;
String VenuImage;
String VenuDescription;
List<String> venuFans;
}
I want to have a producer class to get an xml file as an input and detect the type of xml (venu/artist) then start to create a product object based on the input.
the problem :
I want to create an interface for aggregate the similarity between above two classes so my interface would be:
interface Model {
public String getImage();
public String getName();
public String getWebsite();
public String getdbpedia();
}
Then I can implement this interface in my builder class and above two classes but how about those different methods?
such as getVenuFans / getArtistAlbumName / etc....?
How can I call them from my producer?
this is my builder :
Class Builder implements Model {
public String getImage(){}
public String getName(){}
public String getWebsite(){}
public String getdbpedia(){}
}
and this can be my producer :
Class Producer {
public Producer()
{
Builder b = null;
//assume Venu and Artist implements Model
b = (Builder) new Venu();
//I don't have access to getVenuFans()!
b = (Builder) new Artist();
//I don't have access to getArtistAlbumsName() / etc...
}
}
You don't have access to those methods because you're casting the objects to a Builder, and Builder doesn't have those methods.
I see what you're trying to do, but I don't think it will work. For example, getVenueFans (I'm assuming you mean venue) is only appropriate for the Venue class. It doesn't make sense to try and abstract that into an interface that other non-Venue classes will implement.
I think what you have is good: You've abstracted the common methods into an interface. To call the methods on Venue and Artist, the consuming code will need to cast the objects to the appropriate type, then call the methods on it. And that's not as bad as you might think. It's the consuming code that knows what type it's dealing with (otherwise, why would it be trying to call getVenueFans?), so that's the point where it makes sense to cast and call the method directly.
I'm trying to write a Compare method to compare properties in some POCOs using Reflection to ensure that they've been persisted to the database correctly. For example, let's say I have this POCO:
public class NoahsArk
{
public string Owner { get; set; }
public ICollection<Animal> Animals { get; set; }
}
What I want to do is this:
[Test]
public class Saves_Correctly_To_Database()
{
var noahsArk = new NoahsArk { // some setup code here };
db.Save(noahsArk);
var dbNoahsArk = db.Get<NoahsArk>(noahsArk.Id);
Assert.That(Compare(noahsArk, dbNoahsArk), Is.True);
}
The ORM I'm using is NHibernate. My Compare method looks like this so far:
public static bool EqualsProperties<T>(this T x, T y)
{
var xType = x.GetType();
foreach (var property in xType.GetProperties())
{
if (property.GetValue(x, null).Implements(typeof(ICollection<>)))
{
var xValue = property.GetValue(x, null) as ICollection<T>;
var yValue = property.GetValue(y, null) as ICollection<T>;
}
Object.Implements() is an extension method I wrote to determine if a type implements an interface. As you can see, the method is incomplete. The problem I'm running into is that when I use property.GetValue(x, null), it returns an object, and I don't know how to cast it into its specific generic ICollection type. I need to be able to do this so I can use LINQ to do a x.Contains(y) to compare the two collections for equality. Any idea on how to do this?
P.S. I tried using Compare .NET Objects, but it's giving me a null reference exception somewhere deep within NHibernate. It doesn't properly handle how NHibernate proxies the ICollection for lazy loading. To make matters worse, NHibernate modifies the POCO to support lazy-loading, but this is all done at runtime. In the source code, it looks like you're just working with a regular ICollection, but NHibernate changes this to NHibernate.Collections.Generic.PersistentSet at runtime, and this is what's causing the comparer to fail.
Your question is a bit confusing because you don't need the type parameter T in the declaration of your EqualsProperties method. You just need
public static bool EqualsProperties(this object x, object y)
You then go on to use the same parameter T to cast properties of x and y to ICollection<T>; however, the objects in these collections obviously may have a different type than x and y.
Now to answer your question: you don't need to cast to the correct generic type to use the LINQ Contains method. You can do something like this:
xValue = property.GetValue(x, null);
yValue = property.GetValue(y, null);
if (typeof(IEnumerable).IsInstanceOf(x))
{
IEnumerable<object> xEnumerable = (x as IEnumerable).Cast<object>();
IEnumerable<object> yEnumerable = (y as IEnumerable).Cast<object>();
// use any LINQ method you like now
}
You should also make sure you use the LINQ overloads that take an equality comparer, as your domain objects obviously do not override the Equals method themselves. Otherwise you wouldn't be writing this unit testing code to compare them.
Sharp architecture framework use attribute to decor properties which should be taken into the equals method. See the source code of DomainSignatureAttribute class and EntityWithTypedId<>.Equals method.