How can I make a pointer to a data member in C++/CLI
for example
ref class team
{
List<teamMember^> members;
teamMember^ leader; //the aim is to make it a pointer to an element in the list
void changeLeader(teamMember^% member) //member is an element from members
{
leader=member; //doesn't reference and %member gave an error
}
};
In C++/Cli handles (^) are analoguos to native pointers.
This code will work.
ref class teamMember
{
public bool isLeader;
};
ref class team
{
List<teamMember^> members;
teamMember^ leader;
void changeLeader(teamMember^ member)
{
if(leader != nullptr)
leader.isLeader = false;
leader = member;
leader.isLeader = false;
}
};
Take a look at this and this for more info.
Related
I have a native C++ method, from external unchangable DLL, that expects a std::vector as a argument with 2 native objects. (for example sake, it's an image library returning width/height of a 2 images)
I would like the native objects in the std::vector to be referenced in my own wrapped MyManagedImageObj.
Somehow the std::vector seems to copy values and has no way to add pointers (correct?); so after calling the NativeMethod; I need to copy the properties (width/height) back again to MyManagedImageObj.
I thought about first declaring the std::vec and getting the pointer of the results and put that in MyManagedImageObj as a pointer. But if I understand it correctly std::vector will clean that native memory up once out of scope. (my c++ experience is 1 week; c# long time)
Is there a better way to do this without reassigning the properties one by one?
Ej
The code looks like this:
//create managed object that wraps also native pointer.
MyManagedImageObj^ obj1 = gcnew MyManagedImageObj();
MyManagedImageObj^ obj2 = gcnew MyManagedImageObj();
//keep list of result
List<MyManagedImageObj^>^ resultList;
resultList->Add(obj1);
resultList->Add(obj2);
//call to native method. Dereference pointers of native wrapped objects... not working?
std::vector<DLLNativeImageObj> nativeImageVec { *obj1->GetInstance(), *obj2->GetInstance() };
bool result = otherNativePtr->NativeMethod(nativeImageVec);
//we still need copy it over results now to 'our' managed objects.
int i = 0;
for (DLLNativeImageObj c : nativeImageVec)
{
resultList[i]->ImageHeight = c.imageHeight;
resultList[i]->ImageWidth = c.imageWidth;
++i;
}
The MyManagedImageObj class looks like this:
//MyManagedImageObj.h
public ref class MyManagedImageObj
{
protected:
DLLNativeImageObj* m_Instance;
public:
MyManagedImageObj(DLLNativeImageObj* instance)
: m_Instance(instance)
{
};
~MyManagedImageObj() //destructor will be called whenever we do 'delete'
{
if (m_Instance != nullptr)
{
delete m_Instance;
}
}
!MyManagedImageObj() //finalizer, called by the garbage collector when it's destroys the wrapper object. So safety check to dispose unmanaged item.
{
if (m_Instance != nullptr)
{
delete m_Instance;
}
}
DLLNativeImageObj* GetInstance() //return the pointer to the unmanaged object
{
return m_Instance;
}
property uint32_t ImageWidth
{
public:
uint32_t get()
{
return m_Instance->imageWidth;
}
public:
void set(uint32_t value)
{
m_Instance->imageWidth = value;
}
}
property uint32_t ImageHeight
{
public:
uint32_t get()
{
return m_Instance->imageHeight;
}
public:
void set(uint32_t value)
{
m_Instance->imageHeight = value;
}
}
};
//MyManagedImageObj.cpp
MyManagedImageObj::MyManagedImageObj(new DLLNativeImageObj())
{
// new keyword important: it returns a pointer to the location and does not get deleted when out of scope. Manual delete is required.
}
My question is, that how can I specify a custom object as a role in a model derived from QAbstractListModel so when visualizing it within a ListView I can access its member variables. To have an example here is some simple code example:
This is my class representing my custom object:
class MyCustomObject {
public:
MyCustomObject(Qstring name, Qstring type);
QString getName();
QString getType();
private:
QString name;
QString type;
};
This is how the overridden data() function looks like now (but it is not working) of my MyModel derived from QAbsractListModel:
QVariant MyModel::data(const QModelIndex &index, int role) const {
if (index.row() < 0 || index.row() > m_atoms.count()) {
//if (!index.isValid()) {
return QVariant();
}
const MyData &data = m_data[index.row()];
if(role == SomeRole) {
return data.someString()
}
else if (role == MyCustomRole) {
return data.myCustomObject; // How can I do this?
}
return QVariant();
}
Here I specify the role names in MyModel:
QHash<int, QByteArray> AtomModel::roleNames() const {
QHash<int, QByteArray> roles;
roles[SomeRole] = "someRole";
roles[MyCustomRole] = "myCustomRole";
return roles;
}
and this is how my ListView looks like in QML code with an example how I would like to access MyCustomObject member variables in the delegate:
ListView {
width: 400
height: 400
model: myModel
delegate: Text {
text: "Type: " + myCustomRole.getType() + ", Name: " + myCustomRole.getName() + ", some string: " someRole
}
}
EDIT1: => fix needed copy constructor
When I am adding Q_DECLARE_METATYPE under my MyCustomObject I receive the following error:
call to implicitly-deleted copy constructor of `MyCustomObject`
in instantiation of member function 'QtMetaTypePrivate::QMetaTypeFunctionHelper<MyCustomObject, true>::Construct' requested here
in instantiation of function template specialization 'qRegisterNormalizedMetaType<MyCustomObject>' requested here QtMetaTypePrivate::QMetaTypeFunctionHelper<T>::Construct,
return qRegisterNormalizedMetaType<T>(normalizedTypeName, dummy, defined);
in instantiation of function template specialization 'qRegisterMetaType<MyCustomObject>' requested here
Q_DECLARE_METATYPE(MyCustomObject)
expanded from macro 'Q_DECLARE_METATYPE'
#define Q_DECLARE_METATYPE(TYPE) Q_DECLARE_METATYPE_IMPL(TYPE)
expanded from macro 'Q_DECLARE_METATYPE_IMPL'
const int newId = qRegisterMetaType< TYPE >(#TYPE,
copy constructor of 'MyCustomObject' is implicitly deleted because base class 'QObject' has a deleted copy constructor
class MyCustomObject : public QObject
'QObject' has been explicitly marked deleted here Q_DISABLE_COPY(QObject)
expanded from macro 'Q_DISABLE_COPY'
Class(const Class &) Q_DECL_EQ_DELETE;\
EDIT2:
So I have added all the necessary functions what #Evgeny has suggested. My code now compiles without errors, but I get a qml error on run time saying:
TypeError: Property 'getType' of object QVariant(MyCustomObject) is not a function
I have added Q_INVOKABLE in front of the getType() method and I also deriving MyCustomObject class from public QObject. I have added Q_DECLARE_METATYPE at the bottom of my MyCustomObject header file. In the constructor of MyCustomObject I call qRegisterMetaType<MyCustomObject>("MyCustomObject") and in my main I register the class also like this qmlRegisterType<MyCustomObject>("com.test.mycustomobject", 1, 0, "MyCustomObject")
This is how MyCustomObject class looks like now:
class MyCustomObject : public QObject {
public:
MyCustomObject();
MyCustomObject(Qstring name, Qstring type);
MyCustomObject(const MyCustomObject& obj);
~MyCustomObject();
Q_INVOKABLE QString getName();
Q_INVOKABLE QString getType();
private:
QString name;
QString type;
};
Q_DECLARE_METATYPE(MyCustomObject)
This is how the overridden data() function looks like now of my MyModel derived from QAbsractListModel:
QVariant MyModel::data(const QModelIndex &index, int role) const {
if (index.row() < 0 || index.row() > m_atoms.count()) {
//if (!index.isValid()) {
return QVariant();
}
const MyData &data = m_data[index.row()];
if(role == SomeRole) {
return data.someString()
}
else if (role == MyCustomRole) {
QVariant var; // this is the part, which has changed
var.setValue(data.myCustomObject);
return var;
}
return QVariant();
}
All other functions which I have posted originally are the same.
First of all you need to declare your custom object for Qt metatype system. You should use Q_DECLARE_METATYPE macro for this. Also you may need to use qRegisterMetaType function. Then you should register your object to use it with QML. You should use qmlRegisterType function for that.
Also make sure you use Q_INVOKABLE for your objects methods.
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.
How can I bind InitializerForXXX (non-generic implementation) to IInitializer<XXX> (generic interface) using Ninject Conventions so that requests for an IInitializer<T> resolve a non-generic implementation whose name starts with InitializerFor and end with typeof(T).Name like:
initializerFactory.CreateFor<Blue>(); //resolves InitializerOfBlue
initializerFactory.CreateFor<ShadeOfBlue>(); //resolves InitializerOfShadeOfBlue
where no non-abstract class directly implement IInitializer<T>, and some implementations inherit from other implementations:
InitializerForShadeOfBlue inherits from InitializerForBlue
InitializerForBlue inherits from abstract Initializer<Blue>
abstract Initializer<T> directly implements IInitializer<T>
I'm hoping I can use a .EndsWith(typeof(T).Name) for a given IInitializer<T> convention I can use, because there are literally hundreds of initializers in the ShadeOfxxx vein. If I have to map all of them, I'm better off finding a way to resolve with reflection at runtime.
Given the following:
UPDATE: bindings with custom binding generator (see my answer below for implementation)
void Bootstrap(IBindingRoot kernel)
{
kernel.Bind<IInitializerFactory>()
.To<InitializerFactory>()
.InSingletonScope();
kernel.Bind(scanner =>
scanner.FromThisAssembly().SelectAllClasses()
.WhichAreNotGeneric()
.InheritedFrom(typeof(IComplexContent))
.BindAllInterfaces());
kernel.Bind(scanner =>
scanner.FromThisAssembly().SelectAllClasses()
.WhichAreNotGeneric()
.InheritedFrom(typeof(IInitializer<>))
.BindWith<FirstTypeParameterNameMatchesEndOfBoundClassNameGenerator>());
}
main method
void Main(IEnumerable<string> values)
{
// setup bindings
var kernel = new StandardKernel();
Bootstrap(kernel);
IInitializerFactory initializerFactory =
kernel.Get<IInitializerFactory>();
IInitializer<ShadeOfBlueComplexContent> initializer =
initializerFactory.CreateFor<ShadeOfBlueComplexContent>();
initializer.Initialize(values);
}
initializer factory
interface IInitializerFactory
{
IInitializer<T> CreateFor<T>() where T : class, IComplexContent, new();
}
class InitializerFactory : IInitializerFactory
{
public IInitializer<T> CreateFor<T>() where T : class, IComplexContent, new()
{
return MagicallyGetInitializer<T>();
}
//behind the curtain, whirring noises are heard as 't' is resolved...
private static IInitializer<T> MagicallyGetInitializer<T>()
where T : class, IComplexContent, new()
{
IInitializer<T> i = null;
return i;
}
}
initializers
interface IInitializer<out T> where T : IComplexContent
{
T Initialize(IEnumerable<string> values);
}
abstract class Initializer<T> : IInitializer<T> where T : IComplexContent
{
public abstract T Initialize(IEnumerable<string> values);
}
class InitializerOfBlue : Initializer<Blue>
{
private readonly Blue _content;
public InitializerOfBlue(Blue content) {_content = content;}
public override Blue Initialize(IEnumerable<string> values)
{
_content.BlueSpecificProperty = values.ElementAt(0);
//... populate other blue-specific properties like this
return _content;
}
}
class InitializerOfShadeOfBlue : InitializerOfBlue
{
public InitializerOfShadeOfBlue(ShadeOfBlue content) : base(content){}
}
content models
interface IComplexContent
{
string OneBasicProperty { get; set; }
// other properties are specific to implementation
string UniqueOperation();
}
abstract class BaseComplexContent : IComplexContent
{
public string OneBasicProperty { get; set; }
public abstract string UniqueOperation();
}
class Blue : BaseComplexContent
{
// initializer sets this
public string PropertyForAllKindsOfBlue { get; set; }
// initializer doesn't interact with this
public override string UniqueOperation() {return "I'm plain.";}
}
class ShadeOfBlue : Blue
{
// initializer doesn't interact with this
public override string UniqueOperation() {return "I'm fabulous!";}
}
You are over specifying the class selection
kernel.Bind(scanner =>
scanner.FromThisAssembly().SelectAllClasses()
.WhichAreNotGeneric()
.InheritedFrom(typeof (IInitializer<>))
This is already enough. What you need to do though is to add a custom Binding Generator. That selects IInitializer<Blue> for InitializerForBlue and IInitializer<ShadeOfBlue> for InitializerForShadeOfBlue
https://github.com/ninject/ninject.extensions.conventions/wiki/Projecting-Services-to-Bind
BEGIN SOLUTION CANDIDATE - custom binding generator:
custom binding generator
Thanks for the advice, #RemoGloor and #RubenBartelink. I'm stumped though - the problem is that I wind up binding the IInitializer<Blue> to InitializerOfShadeOfBlue. I need to be able to somehow change the generic type argument from Blue to ShadeOfBlue in the IInitializer<Blue> binding candidate, since IInitializer<ShadeOfBlue> is what will be requested from the factory method at runtime.
Is there a way to modify the generic type argument list of the binding candidate? Or am I barking up the wrong implementation? Any edit suggestions to my OP or this answer are appreciated.
/// <summary>Creates bindings on open generic types where bound implementations'
/// names end with the name of the generic type argument</summary>
public class FirstTypeParameterNameMatchesEndOfBoundClassNameGenerator : IBindingGenerator
{
public IEnumerable<IBindingWhenInNamedWithOrOnSyntax<object>> CreateBindings(Type type, IBindingRoot bindingRoot)
{
if (type == null) throw new ArgumentNullException("type");
if (bindingRoot == null) throw new ArgumentNullException("bindingRoot");
// only consider concrete, non-abstract classes
if (type.IsInterface || type.IsAbstract) yield break;
var bindingType = GetBindingType(type);
if (bindingType != null)
yield return bindingRoot.Bind(bindingType).To(type);
// ARGH! bindingType == IInitializer`1[[Blue]] but I want
// IInitializer`1[[ShadeOfBlue]] for type == ShadeOfBlue
}
private static Type GetBindingType(Type type)
{
Type goodMatch = null;
foreach (var candidate in type.GetInterfaces())
{
// skip non-generic interfaces
if (!candidate.IsGenericType) continue;
// assumption: using argument in first position
var firstArg = candidate.GetGenericArguments().First();
if (!type.Name.EndsWith(firstArg.Name)) continue;
// IInitializer<XXX> matches InitializerOfXXX
goodMatch = candidate;
break;
}
if (goodMatch == null)
{
// if no match on interfaces, walk through the ancestor types
foreach (var candidate in type.GetAllAncestors())
{
goodMatch = GetBindingType(candidate);
if (goodMatch != null) break;
}
}
return goodMatch;
}
Type Extension helper
public static class TypeExtensions
{
// returns all ancestor types starting with the parent
public static IEnumerable<Type> GetAllAncestors(this Type type)
{
for (var current = type.BaseType; current != null; current = current.BaseType)
yield return current;
}
}
END SOLUTION CANDIDATE - custom binding generator
In my program, I have a class that I want to be allocated before entering main(). I'd like to tuck these away in a separate module to keep the clutter out of my code; However, as soon as the module goes out of scope (before main() is entered), the objects are deallocated, leaving me trying to use a null reference in main. A short example:
// main.d
import SceneData;
int main(string[] argv)
{
start.onSceneEnter();
readln();
return 0;
}
// SceneData.d
import Scene;
public
{
Scene start;
}
static this()
{
Scene start = new Scene("start", "test", "test";
}
// Scene.d
import std.stdio;
class Scene
{
public
{
this(string name)
{
this.name = name;
}
this(string name, string descriptionOnEnter, string descriptionOnConnect)
{
this.name = name;
this.descriptionOnEnter = descriptionOnEnter;
this.descriptionOnConnect = descriptionOnConnect;
}
void onSceneEnter()
{
writeln(name);
writeln(descriptionOnEnter);
}
}
private
{
string name;
string descriptionOnEnter;
string descriptionOnConnect;
}
}
I'm still getting used to the concept of modules being the basic unit of encapsulation, as opposed to the class in C++ and Java. Is this possible to do in D, or must I move my initializations to the main module?
Here:
static this()
{
Scene start = new Scene("start", "test", "test");
}
"start" is a local scope variable that shadows global one. Global one is not initialized.
After I have changed this to:
static this()
{
start = new Scene("start", "test", "test");
}
Program crashed no more.