I have coded the following, and am very new to c++, and it feels clumsy. I am trying to give 'spriteBatch' (a unique_Ptr) class scope. Here's the header file:
ref class CubeRenderer : public Direct3DBase
{
public:
CubeRenderer();
~CubeRenderer();
private:
std::unique_ptr<SpriteBatch> spriteBatch;
};
Then in the cpp file Constructor, this:
std::unique_ptr<SpriteBatch> sb(new SpriteBatch(m_d3dContext.Get()));
spriteBatch = std::move(sb);
It just seems clumsy the way I had to create 'sb' and move it to 'spriteBatch'. attempting to assign directly to 'spriteBatch' failed (maybe I simply don't know the proper syntax). Is there a way to avoid needing to use 'sb' & std::move?
Thank you.
The following should work fine:
spriteBatch = std::unique_ptr<SpriteBatch>(new SpriteBatch(m_d3dContext.Get()));
Alternatively, you can avoid repeating the type name with some make_unique function.
spriteBatch = make_unique<SpriteBatch>(m_d3dContext.Get());
There's also the reset member:
spriteBatch.reset(new SpriteBatch(m_d3dContext.Get()));
But, since you mention a constructor, why not just use the member initialization list?
CubeRenderer::CubeRenderer()
: spriteBatch(new SpriteBatch(m_d3dContext.Get())) {}
Related
I am missing something ...
I have a class SocketComm. I have a derived class SocketTCP : public SocketComm.
SocketComm has the following in it:
static SocketComm *Instance; // static pointer to the singleton instance du jour
I am trying to define a method in SocketComm as follows:
static inline SocketTCP *GetTCPclass()
{
// consistent method to return a SocketTCP* cast of SocketComm::Instance (or NULL)
SocketTCP *s = dynamic_cast<SocketTCP *>(Instance);
assert( s != NULL );
return s;
}
I am getting (VS 2010)
error C2680: 'SocketTCP *' : invalid target type for dynamic_cast
What am I missing? SocketComm is abstract -- is that the problem?
The answer seems to be that dynamic_cast needs a full declaration of the target class.
See my comment above.
Yeah, like #ViRusTriNiTy says, I suppose I could have put it in SocketTCP as a static inline. That would probably have worked too. But it seems more logical to me in the base class, and there is no performance reason to make it inline. The compiler will inline it when it can (in SocketComm.cpp) anyway.
According to your comments you are mixing code that belongs to a derived class into a base class. This is the wrong approach and you now see why: SocketTCP' : class must be defined before using in a dynamic_cast.
Just approach this in a different way like say adding a separate helper class that does the dynamic_cast.
I'm new to Vala and so far I think it's pretty cool but I'm having trouble understanding inheritance. I read here that I should use base() to call the parents constructor. Alright, cool, seems understandable but It din't work for me. I kept getting the error on the title. Here is my snippet to show:
public class MyBox : Gtk.Box {
public MyBox(Gtk.Orientation orientation, int spacing) {
// I have to this
this.set_orientation(orientation);
this.set_spacing(spacing);
// I want to do this:
base(orientation, spacing);
//workaround is this:
Object(orientation: orientation, spacing: spacing);
}
}
Please help me understand why Object(....) works but not base(...)
Shouldn't it be the same thing?
This is due to implementation of the C code. When Vala generates a constructor, it generates two C functions a _new function that allocates memory and calls the _construct and a _construct function that initialises the object. When you case the base constructor using base(), it needs a matching _construct function to call. Not all the classes written in C have this; in the VAPI file, you will find has_construct_function = false for some constructors. If this is the case, no chain-up can be done. The base GObject can set properties from arguments, so this becomes the only way to set defaults in the base class.
I'm using lua 5.2.2 with luabind 0.9.
I'd like to be able to add additional class-methods through lua for any classes that I've bound in c++, but I'm unsure how to do it.
The problem is that luabind uses a function as the __index-metamethod for any bound classes instead of a table, so I don't see a way to access the class-methods at all.
e.g., I'm binding my classes like this:
luabind::module(lua)
[
luabind::class_<testClass>("TestClass")
.def(luabind::constructor<>())
.def("TestFunc",&TestFunc)
];
What I essentially want to do is to add a lua-function to the list of methods for this class, and be able to overwrite existing ones:
local t = tableOfClassMethods
local r = t.TestFunc -- Reference to the c++-function we've bound
t.SomeFunction = function(o) end -- New function for all objects of this class
t.TestFunc = function(o) end -- Should overwrite the c++-function of the same name
Any help would be appreciated.
You could use a luabind::object property and register it with the .property method of luabind
Something like this:
//Class
class FunctionCaller
{
public:
luabind::object Fn;
void SetFn(luabind::object NewFn)
{
Fn = NewFn;
};
luabind::object GetFn()
{
return Fn;
};
};
//Binding Code
luabind::class_<FunctionCaller>("FunctionCaller")
.def(luabind::constructor<>())
.property("Fn", &FunctionCaller::Fn, &FunctionCaller::SetFn, &FunctionCaller::GetFn)
Then you just need to call the luabind::object according to the luabind docs.
It's not exactly what you want to do but it could help you overwrite the function I think. You could bind the real function and have a property, check if the luabind::object is non-null, and call it or the native function.
I am completely new to C++\CLI and I have the following problem: I have a class called, for example, MyClass, a few values of which I need to store in memory. I have decided to use List, because it is the most familiar to me, since I was using C# for a long time. So here goes the code:
//Header File
ref class MyClass
{
public:
MyClass(void);
private:
System::Collections::Generic::List<MyClass^> values;
};
//CPP file
MyClass::MyClass(void){
this->values=gcnew System::Collections::Generic::List<MyClass^>();
}
The compiler keeps on saying that there's an error C2582. But if there's no assignment operator, then how should I initialize the List?
Thanks in advance.
values should not be a List<...^>, but a List<...^>^. You want to assign a reference, not to create another clone of the list.
Well, I haven't yet found something that says this is impossible, though I'm starting to think it might be. Can you make this work?
using namespace System;
template <typename T>
void unset(Nullable<T>& var) { var = Nullable<T>(); }
void unset(String^% var) { var=nullptr; }
//this is really a C# class in my situation, so I can't change its types
public ref class Foo
{
public:
property Nullable<Decimal> Dec;
property Nullable<int> Num;
property String^ Str;
};
int main()
{
Foo^ foo = gcnew Foo;
foo->Dec = Decimal(1.2);
foo->Num = 3;
foo->Str = "hi";
unset(foo->Dec);
unset(foo->Num);
unset(foo->Str);
Console::WriteLine(foo->Dec);
Console::WriteLine(foo->Num);
Console::WriteLine(foo->Str);
}
Update: unset is called from a code-generating macro which is called on about 50 params. I'd prefer not to have to go make varieties of the macro for each type.
It isn't possible. Setting a property requires calling the property setter function. There is no way to guess for the called method that it needs to call a function vs can assign the passed variable pointer. If you really want to do this then pass a delegate.
There is actually one .NET language that supports it, VB.NET generates code like this:
T temp = obj->prop;
func(temp)
obj->prop = temp;
There is however a dreadful aliasing problem with that, quite undebuggable. This goes belly up in the (rare) case where func() also uses the property. This is otherwise the way you'd work around the limitation, explicitly in your own code.
Beware that your code is wrong, possibly intentional, you are passing a C++ & reference, not a managed % interior pointer. The compiler is going to bitch about that, you can't create references or pointers to managed objects. They move. Unless the reference is to a variable on the stack. It doesn't otherwise change the answer.
For those who may end up here wondering how I got on with this, I ended up being lucky that the class I was working with was an LLBLGen Entity, so I was able to replace
unset(re->var);
with
{ SD::LLBLGen::Pro::ORMSupportClasses::IEntityField2^ f = re->Fields[#var]; \
if (f->IsNullable) \
f->CurrentValue = nullptr; }