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C# Passing a reference to a generic method to another method


By : AndrewGhost
Date : July 30 2020, 11:00 PM
wish helps you Sure, just create a few methods whose job it is to handle the exceptions, one for returning results and the other for void, and provide something that does your work.
code :
T Handle<T>(Func<T> call)
{
    try
    {
        return call();
    }
    catch(YourException ex)
    {
        return default;
    }
}

void Handle(Action call)
{
    try
    {
        call();
    }
    catch(YourException ex)
    {

    }
}
var result = Handle(() => SomeCallWithVaryingSignature(...));
Handle(() => SomeOtherCall(...));


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After passing a reference to an method, any mods using that reference are not visible outside the method - Ruby?


By : thanh hai
Date : March 29 2020, 07:55 AM
I wish did fix the issue. As Greg mentions, in your example you're creating a new local variable called name that is shadowing your parameter. This is due to behavior called copy-on-write. If you wanted the function to affect the object the parameter references, you could use replace instead of doing an assignment, like this:
code :
def mod_name(name)
  name.replace('JasonB')
end

Given a constrained generic method can I call a non-generic method passing the actual type of the generic parameter


By : user2957587
Date : March 29 2020, 07:55 AM
help you fix your problem As Aliostad said, what your trying to do is no longer generic and it would be better to just use overloads. It looks like you are trying to do something similar to template specialization in C++, where depending on the generic type it calls different methods.
Here is an example where I implemented a sort of generic specialization using reflection, you might be able to apply a similar pattern if overloading method wont work for you. If you can cache the results of reflection and only call GetMethod once then it turns out to be not too slow. Inside a class generic by T there is a method that calls:
code :
if (_serializeDataToStream == null)
    _serializeDataToStream = (Action<BinaryWriter, int, T[]>)GetTypeSpecificSerializationMethod();

_serializeDataToStream(writer, _size, _data);
/// <summary>
/// Returns a delegate that points at the static type specific serialization method
/// </summary>
/// <returns></returns>
private Delegate GetTypeSpecificDeserializationMethod()
{
    if (typeof(T) == typeof(double))
    {
        MethodInfo method = this.GetType().GetMethod("DeserializeDouble", BindingFlags.Static | BindingFlags.NonPublic);
        return Delegate.CreateDelegate(typeof(Action<BinaryReader, int, T[]>), method);
    }
    else if (typeof(T) == typeof(ushort))
    {
        MethodInfo method = this.GetType().GetMethod("DeserializeUshort", BindingFlags.Static | BindingFlags.NonPublic);
        return Delegate.CreateDelegate(typeof(Action<BinaryReader, int, T[]>), method);
    }
    else if (typeof(T) == typeof(DateTime))
    {
        MethodInfo method = this.GetType().GetMethod("DeserializeDateTime", BindingFlags.Static | BindingFlags.NonPublic);
        return Delegate.CreateDelegate(typeof(Action<BinaryReader, int, T[]>), method);
    }
    else if (typeof(T) == typeof(bool))
    {
        MethodInfo method = this.GetType().GetMethod("DeserializeBool", BindingFlags.Static | BindingFlags.NonPublic);
        return Delegate.CreateDelegate(typeof(Action<BinaryReader, int, T[]>), method);
    }

    throw new NotImplementedException("No deserialization method has been setup for type " + typeof(T).FullName);
}

/// <summary>
/// Serialize double[] to BinaryWriter
/// </summary>
/// <param name="writer"></param>
/// <param name="size"></param>
/// <param name="data"></param>
private static void SerializeDouble(BinaryWriter writer, int size, double[] data)
{
    for (int i = 0; i < size; i++)
    {
        writer.Write(data[i]);
    }
}

I'm losing the type of a variable in a generic method when passing to a second generic method with varargs


By : Deepchand Prajapati
Date : March 29 2020, 07:55 AM
it should still fix some issue Varargs are syntactic sugar that translates to an array of the given type by the compiler. That means that a method(Type arg...) will become method(Type[] arg).
In Java, you cannot create arrays of Non-reifiable types (types whose type information is lost by erasure). Therefore, a generic varargs such as printClassVarargs(T ... str) will translate to printClassVarargs(Object[] str), effectively resulting in erasure of the type info. This is what you are observing in your test.
code :
public Test();
  Code:
   0:   aload_0
   1:   invokespecial   #8; //Method java/lang/Object."<init>":()V
   4:   return

public static void main(java.lang.String[]);
  Code:
   0:   ldc #16; //String 5318008
   2:   astore_1
   3:   aload_1
   4:   invokestatic    #18; //Method printClass:(Ljava/lang/Object;)V
   7:   aload_1
   8:   invokestatic    #22; //Method callPrintClass:(Ljava/lang/Object;)V
   11:  iconst_1
   12:  anewarray   #25; //class java/lang/String
   15:  dup
   16:  iconst_0
   17:  aload_1
   18:  aastore
   19:  invokestatic    #27; //Method printClassVarargs:([Ljava/lang/Object;)V
   22:  aload_1
   23:  invokestatic    #31; //Method callPrintClassVarargs:(Ljava/lang/Object;)V
   26:  return

public static void printClass(java.lang.Object);
  Code:
   0:   getstatic   #40; //Field java/lang/System.out:Ljava/io/PrintStream;
   3:   aload_0
   4:   invokevirtual   #46; //Method java/lang/Object.getClass:()Ljava/lang/Class;
   7:   invokevirtual   #50; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V
   10:  return

public static void printClassVarargs(java.lang.Object[]);
  Code:
   0:   getstatic   #40; //Field java/lang/System.out:Ljava/io/PrintStream;
   3:   aload_0
   4:   invokevirtual   #46; //Method java/lang/Object.getClass:()Ljava/lang/Class;
   7:   invokevirtual   #59; //Method java/lang/Class.getComponentType:()Ljava/lang/Class;
   10:  invokevirtual   #50; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V
   13:  return

public static void callPrintClass(java.lang.Object);
  Code:
   0:   aload_0
   1:   invokestatic    #18; //Method printClass:(Ljava/lang/Object;)V
   4:   return

public static void callPrintClassVarargs(java.lang.Object);
  Code:
   0:   iconst_1
   1:   anewarray   #3; //class java/lang/Object
   4:   dup
   5:   iconst_0
   6:   aload_0
   7:   aastore
   8:   invokestatic    #27; //Method printClassVarargs:([Ljava/lang/Object;)V
   11:  return

}

Passing a reference type to generic method with Unity


By : Fieras
Date : March 29 2020, 07:55 AM
will help you You have a dependency in your parseCSV method. Therefore, you should inject that into your class as well. There are many ways to do that but I prefer, and I have seen many other devs also prefer, constructor injection.
Thus all you need is an interface and then inject an instance of a class which implements the interface into your constructor like this:
code :
public interface IFileHelperEngine<T> where T : class
{
    T[] ReadFile(string inputFileName);
}

public class Handler<T> : IHandler<T> where T : class
{
    private IFileHelperEngine<T> fileHelperEngine;
    public Handler(IFileHelperEngine<T> fileHelperEngine) //<----See this.
    {
        this.fileHelperEngine = fileHelperEngine;
    }
    public T[] parseCSV(string InputFileName)
    {
        if (File.Exists(InputFileName))
        {
            _inputFileName = InputFileName;
            return this.fileHelperEngine.ReadFile(_inputFileName); //<--and this
        }

        throw new IOException($"{InputFileName} not found!");
    }
}

How to create instance of generic class passing a method reference in constructor with kotlin


By : theNotoriousHxc
Date : March 29 2020, 07:55 AM
I wish this helpful for you A Kotlin lambda is usually translated as a FunctionX object, being X the number of parameters it has, so if you're looking for the representation of a lambda function like (Int) -> Unit it would be Function1 so you could simply do:
code :
entityClass.getConstructor(View::class.java, Function1::class.java)
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