I have the following Xamarin.Mac code:
[Register("Swizzler")]
public class Swizzler : NSObject
{
[DllImport("/usr/lib/libobjc.dylib")] public static extern IntPtr class_getInstanceMethod(IntPtr classHandle, IntPtr Selector);
[DllImport("/usr/lib/libobjc.dylib")] public static extern bool method_exchangeImplementations(IntPtr m1, IntPtr m2);
public void AttemptSwizzle()
{
var swizzledClassPtr = Class.GetHandle("Swizzled");
var swizzlerClassPtr = Class.GetHandle("Swizzler");
SwizzleInstanceMethod(swizzledClassPtr, new Selector("originalMethod"), swizzlerClassPtr, new Selector("newMethod"));
var swizzled = new Swizzled();
swizzled.PerformSelector(new Selector("originalMethod"));
}
internal void SwizzleInstanceMethod(IntPtr originalClassPtr, Selector originalSelector, IntPtr newClassPtr, Selector newSelector)
{
var originalMethod = class_getInstanceMethod(originalClassPtr, originalSelector.Handle);
var swizzledMethod = class_getInstanceMethod(newClassPtr, newSelector.Handle);
method_exchangeImplementations(originalMethod, swizzledMethod);
}
[Export("newMethod")]
public void NewMethod()
{
Console.WriteLine("New method called");
}
}
[Register("Swizzled")]
internal class Swizzled : NSObject
{
[Export("originalMethod")]
public void OriginalMethod()
{
Console.WriteLine("Original method called");
}
}
Code sample at https://github.com/alataffective/XamarinSwizzler.
When calling new Swizzler().AttemptSwizzle() I get the following output:
SomeMethod called
That is, the swizzling isn't happening. Why not?
The problem is that you exchange implementations of exported C# methods. Exports share a single implementation, that performs it's own mapping from selectors to C# methods. Therefore, switching them has no effect. You can check it yourself when you call method_getImplementation() for both exported methods and compare returned values.
Just try swizzling original Objective-C methods of original Objective-C classes and you'll see that it works:
public void AttemptSwizzle()
{
var swizzledClassPtr = Class.GetHandle("NSWindow");
var swizzlerClassPtr = Class.GetHandle("NSWindow");
SwizzleInstanceMethod(swizzledClassPtr, new Selector("title"), swizzlerClassPtr, new Selector("tabbingIdentifier"));
var swizzled = new NSWindow();
swizzled.TabbingIdentifier = "TabbingIdentifier";
var result = swizzled.Title;
Console.WriteLine($"title:{result}");
}
If you want to swizzle original Objective-C method with a plain, not exported C# one, you still can, making use of the following methods:
Marshal.GetFunctionPointerForDelegate()
method_setImplementation()
method_getImplementation()
Related
I have two wrappers written in C++/CLI as followings.
One wrapper get a native class handle and it send this native handle to another class, however, I got a compile error.
I think there are some work-around,
1) #pragme make_public()
2) using IntPtr(sender) and static_cast with IntPtr.ToPointer(receiver).
What is the best solution?
namespace AWrapper {
public ref class AClass
{
public:
NativeClass* GetInfo() { return nativeClass; }
...
private:
NativeClass* nativeClass;
}
namespace BWrapper {
...
void ImageSensor::SetClass(AWrapper::AClass^ aclass)
{
NativeClass* native_tpr;
native_tpr = aclass->GetInfo(); // Not visible, like private
}
}
I'm trying to create an event aggregator in C++/CLI, I know that the valid syntax in C# would be as follows:
//C# code
public partial class Foo : UserControl, IView, IDisposable
{
private IEventAggregator _aggregator;
public Foo(IEventAggregator aggregator)
{
InitializeComponent();
this._aggregator = aggregator;
if (this._aggregator == null)
throw new Exception("null pointer");
_subToken =_aggregator.GetEvent<fooEvent>().Subscribe(Handler, ThreadOption.UIThread, false);
}
private SubscriptionToken _subToken = null;
private void Handler(fooEventPayload args)
{
//this gets run on the event
}
}
However directly converting this to C++/CLI gives the error "a pointer-to-member is not valid for a managed class" on the indicated line. Is there a workaround? I think it has something to do with how C# generates "Action".
//C++/CLI code
ref class Foo
{
public:
Foo(IEventAggregator^ aggregator)
{
void InitializeComponent();
this->_aggregator = aggregator;
if (this->_aggregator == nullptr)
throw gcnew Exception("null pointer");
//error in the following line on Hander, a pointer-to-member is not valid for a managed class
_subToken = _aggregator->GetEvent<fooEvent^>()->Subscribe(Handler, ThreadOption::UIThread, false);
private:
IEventAggregator ^ _aggregator;
SubscriptionToken ^ _addActorPipelineToken = nullptr;
void Handler(fooEventPayload^ args)
{
//this gets run on the event
}
}
You need to explicitly instantiate the delegate object, rather than allowing C# to do this for you.
_subToken = _aggregator->GetEvent<fooEvent^>()->Subscribe(
gcnew Action<fooEventPayload^>(this, &Foo::Handler), ThreadOption::UIThread, false);
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Explicitly instantiate the delegate.
// ^^^^ Object to call the delegate on.
// ^^^^^^^^^^^^^ C++-style reference to the method.
So i have a class that makes an array list for me and i need to access it in another class through a constructor but i don't know what to put into the constructor because all my methods in that class are just for manipulating that list. im either getting a null pointer exception or a out of bounds exception. ive tried just leaving the constructor empty but that dosent seem to help. thanks in advance. i would show you code but my professor is very strict on academic dishonesty so i cant sorry if that makes it hard.
You are confusing the main question, with a potential solution.
Main Question:
I have a class ArrayListOwnerClass with an enclosed arraylist property or field.
How should another class ArrayListFriendClass access that property.
Potential Solution:
Should I pass the arraylist from ArrayListOwnerClass to ArrayListFriendClass,
in the ArrayListFriendClass constructor ?
It depends on what the second class does with the arraylist.
Instead of passing the list thru the constructor, you may add functions to read or change, as public, the elements of the hidden internal arraylist.
Note: You did not specify a programming language. I'll use C#, altought Java, C++, or similar O.O.P. could be used, instead.
public class ArrayListOwnerClass
{
protected int F_Length;
protected ArrayList F_List;
public ArrayListOwnerClass(int ALength)
{
this.F_Length = ALength;
this.F_List = new ArrayList(ALength);
// ...
} // ArrayListOwnerClass(...)
public int Length()
{
return this.F_Length;
} // int Length(...)
public object getAt(int AIndex)
{
return this.F_List[AIndex];
} // object getAt(...)
public void setAt(int AIndex, object AValue)
{
this.F_List[AIndex] = AValue;
} // void setAt(...)
public void DoOtherStuff()
{
// ...
} // void DoOtherStuff(...)
// ...
} // class ArrayListOwnerClass
public class ArrayListFriendClass
{
public void UseArrayList(ArrayListOwnerClass AListOwner)
{
bool CanContinue =
(AListOwner != null) && (AListOwner.Length() > 0);
if (CanContinue)
{
int AItem = AListOwner.getAt(5);
DoSomethingWith(Item);
} // if (CanContinue)
} // void UseArrayList(...)
public void AlsoDoesOtherStuff()
{
// ...
} // void AlsoDoesOtherStuff(...)
// ...
} // class ArrayListFriendClass
Note, that I could use an indexed property.
I haven't any idea about how to do the same in c++/cli.
Is not clear for me how a I can create delegate and how I can invoke it.
Can someone help me?
Thanks.
public class Writer {
internal Dictionary<Type, Action<object>> Reflective = new Dictionary<Type, Action<object>>();
public Writer()
{
Reflective.Add(typeof(float), (value) => Write((float)value));
Reflective.Add(typeof(double), (value) => Write((double)value));
}
public void Write(float value)
{
Console.WriteLine("Float");
}
public void Write(double value)
{
Console.WriteLine("Double");
}
public void Write<T>(T[] values)
{
var method = this.Reflective[typeof(T)];
foreach (var value in values)
{
method(value);
}
}
}
I won't write the whole thing for you, but here's a couple of the non-obvious things to get you started:
typeof(float) ==> System::Single::typeid
// I like to specify the full namespace for explicitness.
Lambdas: C++/CLI does not support lambdas. You'll need to declare a full-fledged method, and construct a delegate to that. Fortunately, you already have that, your two Write methods should work. Don't forget when declaring the delegate, if it's an instance method, you'll need to specify the object to invoke the function on, which should be this in your code.
I'm trying to test if the method I want to test calls some external (mock) object properly.
Here is the sample code:
using System;
using Rhino.Mocks;
using NUnit.Framework;
namespace RhinoTests
{
public abstract class BaseWorker
{
public abstract int DoWork(string data);
}
public class MyClass
{
private BaseWorker worker;
public BaseWorker Worker
{
get { return this.worker; }
}
public MyClass(BaseWorker worker)
{
this.worker = worker;
}
public int MethodToTest(string data)
{
return this.Worker.DoWork(data);
}
}
[TestFixture]
public class RhinoTest
{
[Test]
public void TestMyMethod()
{
BaseWorker mock = MockRepository.GenerateMock<BaseWorker>();
MyClass myClass = new MyClass(mock);
string testData = "SomeData";
int expResponse = 10;
//I want to verify, that the method forwards the input to the worker
//and returns the result of the call
Expect.Call(mock.DoWork(testData)).Return(expResponse);
mock.GetMockRepository().ReplayAll();
int realResp = myClass.MethodToTest(testData);
Assert.AreEqual(expResponse, realResp);
}
}
}
When I run this test, I get:
TestCase 'RhinoTests.RhinoTest.TestMyMethod'
failed: System.InvalidOperationException : Invalid call, the last call has been used or no call has been made (make sure that you are calling a virtual (C#) / Overridable (VB) method).
at Rhino.Mocks.LastCall.GetOptions[T]()
at Rhino.Mocks.Expect.Call[T](T ignored)
RhinoTest.cs(48,0): at RhinoTests.RhinoTest.TestMyMethod()
The exception is thrown on the Expect.Call line, before any invocation is made.
How do I approach this - i.e. how to check if the method under test properly forwards the call?
This is .Net 2.0 project (I can no change this for now), so no "x =>" syntax :(
I have to admit, I'm not entirely sure what's going on here, but using Rhino.Mocks 3.6 and the newer syntax, it works fine for me:
[Test]
public void TestMyMethod()
{
MockRepository mocks = new MockRepository();
BaseWorker mock = mocks.StrictMock<BaseWorker>();
MyClass myClass = new MyClass(mock);
string testData = "SomeData";
int expResponse = 10;
using (mocks.Record())
{
//I want to verify, that the method forwards the input to the worker
//and returns the result of the call
Expect.Call(mock.DoWork(testData)).Return(expResponse);
}
using (mocks.Playback())
{
int realResp = myClass.MethodToTest(testData);
Assert.AreEqual(expResponse, realResp);
}
}
It doesn't have anything to do with the Rhino.Mocks version. With the old syntax, I get the same error as you're getting. I didn't spot any obvious errors in your code, but then again, I'm used to this using syntax.
Edit: removed the var keyword, since you're using .NET 2.0.