First of all, sorry for the title. I didn't know exactly how to give name to the situation I'm facing.
I am developing a project in C++ that will run over QNX (so answers that recur to Windows libraries are not good).
I have one class that holds and manipulates all my data, and a few other classes that are responsible for dealing with my UI.
The UI manipulating classes include my data class, and when they are initialized, they all get a pointer to the same data object (each one uses different parts of it, though). And the normal flow of the program is the UI receiving events from the user, and then making calls to the data class and updating itself, according to the data class replies. That all works just fine.
The problem is, sometimes it might happen that this data class object receives calls from other sorts of external events (let's say a call from a class responsible for communication), asking it to change some of it's values. After doing so, it would have to update the UI (thus, having to make a call to the UI classes).
The actual objects to all the classes (UI and data) are contained by the "main" class. But as the UI classes include the data class to be able to call it's methods, the data class including UI classes in order to be able to call their methods would fall into mutual inclusion.
The problem resumes, in a very simplistic way (I am just trying to give a visual example of the information flow), to something like this:
main.cpp
#include "interface.h"
#include "data.h"
Data data_;
Interface interface_;
// Initialize all data from files, etc
data_.Init();
// Call the interface that will use all of this data
interface_.Init(&data_);
while(1);
interface.h
#include "data.h"
class Interface
{
Data *data_;
void Init(Data *data);
void ReceiveEvent();
void ChangeScreen (int value);
};
interface.cpp
#include "interface.h"
void Interface::Init(Data *data)
{
// Get the pointer locally
data_ = data;
}
// Function called when a (for example) a touch screen input is triggered
void Interface::ReceiveEvent()
{
ChangeScreen(data_->IncreaseParam1());
}
void Interface::ChangeScreen (int value);
{
// Set the value on screen
}
data.h
class Data
{
int param 1;
void Init();
int IncreaseParam1();
void ReceiveExternalEvent();
};
**data.cpp"
#include "data.h"
void Data::Init()
{
// The value actually come from file, but this is enough for my example
param1 = 5;
}
int IncreaseParam1()
{
param1 += 5;
return param1;
}
// This is called from (for example) a communication class that has a
// pointer to the same object that the interface class object has
void ReceiveExternalEvent()
{
IncreaseParam1();
// NOW HERE IT WOULD HAVE TO CALL A METHOD TO UPDATE THE INTERFACE
// WITH THE NEW PARAM1 VALUE!
}
I hope I made myself clear enough.
Can someone please give me ideas on how to deal with this situation?
Thanks a lot in advance!
Both Data and Interface are singletons. You expect to only have one instance of each class in existence. So:
Class Data {
public:
static Data *instance;
Data()
{
instance=this;
}
// Everything else that goes into Data, etc...
};
Class Interface {
public:
static Interface *instance;
Interface()
{
instance=this;
}
// Everything else that goes into Data, etc...
};
Now, ReceiveExternalEvent() will simply invoke Data::instance->method() and/or Interface::instance->method(), and so on...
This is a classical singleton design pattern.
Also, you might find some additional Google food of likely interest to you: "model view controller" and "mvc".
A VCL component newbie here, so pardon me if this is a stupid question...
I'm trying to make a TComboBox component with default items in it upon dropped onto the form, i.e. a TMonthComboBox that will have the list of months in its Items list, when dropped on the form.
I've found that trying to access the Items property during Construction will result in a "Control '' has no parent window" error if I try to drop such combobox on the form.
here is (part of) the constructor:
__fastcall TMonthCombo::TMonthCombo(TComponent *Owner):TComboBox(Owner)
{
this->Style = csDropDownList; // this is okay
this->Items->Add("January"); // This is causing problem
}
I figured that the problem is stemming from the fact that the Items property is not available yet at this point of the construction.
Is there anyway to make sure the component is ready to accept values into its Items property, within the component source code itself (i.e. not adding the list items in the Properties Editor at design time)?
Before anyone tells me to "Just add the items in your Application code at run time", I have to explain that this ComboBox will be used quite frequently in many places, and Month selection is just a simple example I used to explain the problem, the actual values I want to put in the ComboBox is much more varied and most of the time, dynamic in nature. It also have to response to the user selection in varied ways.
I have tried the run-time way, but it's getting very tedious. That's why I'm making it into a component, so that it will handle itself without me having to repeatedly input multiple versions of codes just to populate the ComboBoxes.
Thanks for any help.
Edit: After tried manlio's solution, the ComboBox has an odd look in run-time:
The ComboBox has double image at run time. What have I done wrong?
__fastcall TYearCombo::TYearCombo(TComponent* Owner) : TComboBox(Owner), init_items(true)
{
}
//---------------------------------------------------------------------------
void __fastcall TYearCombo::CreateWnd()
{
unsigned short yr, mn, dy;
this->Width = 90;
this->Style = csDropDownList;
this->DropDownCount = 11;
TDate d = Today();
d.DecodeDate(&yr, &mn, &dy);
year = yr;
if (init_items)
{
init_items = false;
TComboBox::CreateWnd();
Items->BeginUpdate();
for(int i=year-5; i<=year+5; i++)
{
Items->Add(IntToStr(i));
}
this->ItemIndex = 5;
Items->EndUpdate();
}
}
//---------------------------------------------------------------------------
You can try this:
Override the CreateWnd virtual method and add a init_items private data member:
class TMonthCombo : public TComboBox
{
// ...
protected:
virtual void __fastcall CreateWnd();
private:
bool init_items;
// ...
};
Set the init_items flag:
TMonthCombo::TMonthCombo(TComponent *Owner) : TComboBox(Owner),
init_items(true)
{
// ...
}
Inside CreateWnd you can add new items:
void __fastcall TMonthCombo::CreateWnd()
{
TComboBox::CreateWnd();
if (init_items)
{
init_items = false;
Items->BeginUpdate();
Items->Add("January");
// ...
Items->EndUpdate();
}
}
Further notes:
"Control has no parent" in Create ComboBox (TComboBox requires an allocated HWND in order to store strings in its Items property).
simply cast the constructor's Owner parameter to TWinControl and assign the result to the component's Parent property isn't a solution:
TMonthCombo::TMonthCombo(TComponent *Owner) : TComBoBox(Owner)
{
Parent = static_cast<TWinControl *>(Owner);
// ...
}
the assignment solves the "Control has no parent window error" but creates another problem: the form is always the component's parent (you cannot add the form to a different container).
I have 3 object, let's call them Main, Manager & Item.
The Manager needs to have an array of Items. These Items are added to the Manager from the Main object.
I'd like to know how should I pass the Items to the Manager in order to make them live even outside the Main() function scope, but at the same time, being able to delete them when the Manager is destroyed.
NOTE
Item, inside Manager, have to be a pointer because I need to check for NULL items
So far I have something like this (not actual code for short):
Main
{
Manager* Man;
Main()
{
Man = new Manager(/**/); //i use a pointer because i need this object to persist;
Item* it = new Item(/**/);
Man->AddItem(it);
}
~Main()
{
delete(Man);
}
}
Manager
{
Item* ItemArchive[15];
void AddItem(Item* item)
{
ItemArchive[index] = item;
}
~Manager()
{
for(int i=0;i<archiveLength;i++)
delete(ItemArchive[i]); //Here i get a runtime error,most probably an
//access violation,can't be more specific
//because Unreal Engine doesn't give me that info
}
}
Item
{
//just a basic object
}
So my question is, how can I create the objects in the Main and then being able to use and delete them inside the Manager?
Consider using std::unique_ptr<Item> and pass ownership from Main to the Manager:
#include <vector>
#include <memory>
class Item {};
class Manager {
std::vector<std::unique_ptr<Item>> item_archive;
public:
void addItem(std::unique_ptr<Item> item){
item_archive.push_back(std::move(item));
}
};
int main() {
Manager manager;
auto item = std::make_unique<Item>(); // C++14
//auto item = std::unique_ptr<Item>(new Item); // C++11
manager.addItem(std::move(item));
}
This way, the items will be deleted when the Manager is destroyed without you having to write a destructor.
I suggest using std::vector instead of an array because it simplifies the management of the item archive.
It is impossible to tell what exactly is giving you the runtime error as you have not posted real code but using std::vector and std::unique_ptr instead will most likely fix it.
Live demo
There's no reason that Manager is not allowed to delete the Items. Your error could be that you're exceeding the ItemArchive array or deleting objects twice? It's hard to tell since you've re-written the code for the question.
I'd say try and use a system that you can debug and then you'll learn a lot quicker! Debuggers are just amazing things.
I've designed an object inherits from CDialog (called NBDialog, and some derived objects of controls, such as CEdit, CDateTimeCtrl, CComboBox etc.
The NBDialog is one project, and the controls are in other projects.
Naturally, All of the controls are put on the dialog and use dialog's methods, so I have to
#include NBDialog.h, and to add its .lib file for the linker.
I also want to handle all those controls from the dialog, so I wrote in NBDialog.h the following lines:
class NBCommonEditBox;
class NBDateTimeCtrl;
class NBCommonComboBox;
CMapWordToOb* NBGetEditBoxMap();
NBCommonEditBox* NBGetEditBoxById(unsigned long ID);
CMapWordToOb* NBGetDateTimeMap();
NBDateTimeCtrl* NBGetDateTimeById(unsigned long ID);
CMapWordToOb* NBGetComboBoxMap();
NBCommonComboBox* NBGetComboBoxById(unsigned long ID);
This way NBDialog.h doesn't know the context of the object, but it knows they are exist and stores them in the maps.
Now I want to extend the NBDialog project and add a method which will get the print information of all controls, so all objects which inhertied from NBDialog will be able to use this method. The print information is defined in the controls implementation.
EDIT: If I write this method in NBDialog.cpp, I can't compile it, because NBDialog doesn't know the context of the controls' classes:
CStringList* NBDialog::NBGetMainTexts()
{
CStringList* mainTexts = new CStringList();
POSITION pos;
WORD key;
NBCommonEditBox* currEdit = NULL;
for (pos = this->NBGetEditBoxMap()->GetStartPosition(); pos != NULL;)
{
this->NBGetEditBoxMap()->GetNextAssoc(pos, key, (CObject*&)currEdit);
currEdit->NBStringsToPrint(mainTexts);
}
return mainTexts;
}
Is there a way to write the desired method?
Easiest way is to define an interface for this and add that interface instead of the CObject. The interface can offer a method to get hold of the control itself. Don;t be afraid of multiple inheritance - yes it can have a slight performance penalty but it is not going to be an issue for you. In this case it will be similar to interface inheritance in Java since you would use a pure interface.
You could also implement this in a similar way that avoids multiple inheritance but it adds more complexity that you don't need.
// Interface goes in the NBDialog project
class INBControl {
public:
virtual ~INBControl() = 0;
virtual CWnd* getWnd() = 0;
virtual void getStringsToPrint(CStringList& strings) = 0;
};
inline INBControl::~INBControl() {}
class NBCommonComboBox : public CComboBox, public INBControl
{
public:
// ... stuff ...
virtual CWnd* getWnd() {
return this;
}
virtual void getStringsToPrint(CStringList& strings) {
strings.AddTail("foo"); // for example
}
};
// NBDialog
#include <map>
class NBDialog : public CDialog
{
public:
// .. stuff ..
private:
typedef std::map<int, INBControl*> ControlMap;
ControlMap control_map_;
};
void NBDialog::addNBControl(INBControl* control, int id)
{
CWnd* wnd = control->getWnd();
// Do stuff with the control such as add it
control_map_[id] = control;
}
// let the caller be responsible for [de]allocation of the string list
void NBDialog::NBGetMainTexts(CStringList& texts)
{
ControlMap::iterator i = control_map_.begin();
ControlMap::iterator e = control_map_.end();
for(; i != e; ++i) {
i->second->getStringsToPrint(texts);
}
}
Alternatively use a custom windows message and iterate all the controls, down-casting to CWnd and using SendMessage on its HWND. Each control will need to handle your custom windoes mesaage. You could pass a pointer to the string list in the LPARAM of the message. This apprach is flexible but somewhat brittle/unsafe and could crash if you end up using the same message ID for something else by accident.
Your implementation file (NBDialog.cpp) is free to #include the necessary headers to make this work (presumably things like NBCommonComboBox.h, etc.) Because the .cpp file isn't #include'd by anything you won't cause any circular include problems.
Warning: This is super in-depth. I understand if you don't even want to read this, this is mostly for me to sort out my thought process.
Okay, so here's what I'm trying to do. I've got these objects:
When you click on one (or select several) it should display their properties on the right (as shown). When you edit said properties it should update the internal variables immediately.
I'm trying to decide on the best way to do this. I figure the selected objects should be stored as a list of pointers. It's either that, or have an isSelected bool on each object, and then iterate over all of them, ignoring the non-selected ones, which is just inefficient. So we click on one, or select several, and then the selectedObjects list is populated. We then need to display the properties. To keep things simple for the time being, we'll assume that all objects are of the same type (share the same set of properties). Since there aren't any instance-specific properties, I figure we should probably store these properties as static variables inside the Object class. Properties basically just have a name (like "Allow Sleep"). There is one PropertyManager for each type of property (int,bool,double). PropertyManagers store all the values for properties of their respective type (this is all from the Qt API). Unfortunately, because PropertyManagers are required to create Properties I can't really decouple the two. I suppose this means that I have to place the PropertyManagers with the Properties (as static variables). This means we have one set of properties, and one set of property managers to manage all the variables in all the objects. Each property manager can only have one callback. That means this callback has to update all the properties of its respective type, for all objects (a nested loop). This yields something like this (in pseudo-code):
function valueChanged(property, value) {
if(property == xPosProp) {
foreach(selectedObj as obj) {
obj->setXPos(value);
}
} else if(property == ...
Which already bothers me a little bit, because we're using if statements where we shouldn't need them. The way around this would be to create a different property manager for every single property, so that we can have unique callbacks. This also means we need two objects for each property, but it might be a price worth paying for cleaner code (I really don't know what the performance costs are right now, but as I know you'll also say -- optimize when it becomes a problem). So then we end up with a ton of callbacks:
function xPosChanged(property, value) {
foreach(selectedObj as obj) {
obj->setXPos(value);
}
}
Which eliminates the entire if/else garbage but adds a dozen more event-listeners. Let's assume I go with this method. So now we had a wad of static Properties, along with their corresponding static PropertyManagers. Presumably I'd store the list of selected objects as Object::selectedObjects too since they're used in all the event callbacks, which logically belong in the object class. So then we have a wad of static event callbacks too. That's all fine and dandy.
So now when you edit a property, we can update the interal variables for all the selected objects via the event callback. But what happens when the internal variable is updated via some other means, how do we update the property? This happens to be a physics simulator, so all the objects will have many of their variables continuously updated. I can't add callbacks for these because the physics is handled by another 3rd party library. I guess this means I just have to assume all the variables have been changed after each time step. So after each time step, I have to update all the properties for all the selected objects. Fine, I can do that.
Last issue (I hope), is what values should we display when multiple objects are selected an there is an inconsistency? I guess my options are to leave it blank/0 or display a random object's properties. I don't think one option is much better than the other, but hopefully Qt provides a method to highlight such properties so that I can at least notify the user. So how do I figure out which properties to "highlight"? I guess I iterate over all the selected objects, and all their properties, compare them, and as soon as there is a mismatch I can highlight it. So to clarify, upon selected some objects:
add all objects to a selectedObjects list
populate the properties editor
find which properties have identical values and update the editor appropriately
I think I should store the properties in a list too so that I can just push the whole list onto the properties editor rather than adding each property individually. Should allow for more flexibility down the road I think.
I think that about covers it... I'm still not certain how I feel about having so many static variables, and a semi-singleton class (the static variables would be initialized once when the first object is created I guess). But I don't see a better solution.
Please post your thoughts if you actually read this. I guess that's not really a question, so let me rephrase for the haters, What adjustments can I make to my suggested design-pattern to yield cleaner, more understandable, or more efficient code? (or something along those lines).
Looks like I need to clarify. By "property" I mean like "Allow Sleeping", or "Velocity" -- all objects have these properties -- their VALUES however, are unique to each instance. Properties hold the string that needs to be displayed, the valid range for the values, and all the widget info. PropertyManagers are the objects that actually hold the value. They control the callbacks, and the value that's displayed. There is also another copy of the value, that's actually used "internally" by the other 3rd party physics library.
Trying to actually implement this madness now. I have an EditorView (the black area drawing area in the image) which catches the mouseClick event. The mouseClick events then tells the physics simulator to query all the bodies at the cursor. Each physics body stores a reference (a void pointer!) back to my object class. The pointers get casted back to objects get pushed onto a list of selected objects. The EditorView then sends out a signal. The EditorWindow then catches this signal and passes it over to the PropertiesWindow along with the selected objects. Now the PropertiesWindow needs to query the objects for a list of properties to display... and that's as far as I've gotten so far. Mind boggling!
The Solution
/*
* File: PropertyBrowser.cpp
* Author: mark
*
* Created on August 23, 2009, 10:29 PM
*/
#include <QtCore/QMetaProperty>
#include "PropertyBrowser.h"
PropertyBrowser::PropertyBrowser(QWidget* parent)
: QtTreePropertyBrowser(parent), m_variantManager(new QtVariantPropertyManager(this)) {
setHeaderVisible(false);
setPropertiesWithoutValueMarked(true);
setIndentation(10);
setResizeMode(ResizeToContents);
setFactoryForManager(m_variantManager, new QtVariantEditorFactory);
setAlternatingRowColors(false);
}
void PropertyBrowser::valueChanged(QtProperty *property, const QVariant &value) {
if(m_propertyMap.find(property) != m_propertyMap.end()) {
foreach(QObject *obj, m_selectedObjects) {
obj->setProperty(m_propertyMap[property], value);
}
}
}
QString PropertyBrowser::humanize(QString str) const {
return str.at(0).toUpper() + str.mid(1).replace(QRegExp("([a-z])([A-Z])"), "\\1 \\2");
}
void PropertyBrowser::setSelectedObjects(QList<QObject*> objs) {
foreach(QObject *obj, m_selectedObjects) {
obj->disconnect(this);
}
clear();
m_variantManager->clear();
m_selectedObjects = objs;
m_propertyMap.clear();
if(objs.isEmpty()) {
return;
}
for(int i = 0; i < objs.first()->metaObject()->propertyCount(); ++i) {
QMetaProperty metaProperty(objs.first()->metaObject()->property(i));
QtProperty * const property
= m_variantManager->addProperty(metaProperty.type(), humanize(metaProperty.name()));
property->setEnabled(metaProperty.isWritable());
m_propertyMap[property] = metaProperty.name();
addProperty(property);
}
foreach(QObject *obj, m_selectedObjects) {
connect(obj, SIGNAL(propertyChanged()), SLOT(objectUpdated()));
}
objectUpdated();
}
void PropertyBrowser::objectUpdated() {
if(m_selectedObjects.isEmpty()) {
return;
}
disconnect(m_variantManager, SIGNAL(valueChanged(QtProperty*, QVariant)),
this, SLOT(valueChanged(QtProperty*, QVariant)));
QMapIterator<QtProperty*, QByteArray> i(m_propertyMap);
bool diff;
while(i.hasNext()) {
i.next();
diff = false;
for(int j = 1; j < m_selectedObjects.size(); ++j) {
if(m_selectedObjects.at(j)->property(i.value()) != m_selectedObjects.at(j - 1)->property(i.value())) {
diff = true;
break;
}
}
if(diff) setBackgroundColor(topLevelItem(i.key()), QColor(0xFF,0xFE,0xA9));
else setBackgroundColor(topLevelItem(i.key()), Qt::white);
m_variantManager->setValue(i.key(), m_selectedObjects.first()->property(i.value()));
}
connect(m_variantManager, SIGNAL(valueChanged(QtProperty*, QVariant)),
this, SLOT(valueChanged(QtProperty*, QVariant)));
}
With a big thanks to TimW
Did you have a look at Qt's (dynamic) property system?
bool QObject::setProperty ( const char * name, const QVariant & value );
QVariant QObject::property ( const char * name ) const
QList<QByteArray> QObject::dynamicPropertyNames () const;
//Changing the value of a dynamic property causes a
//QDynamicPropertyChangeEvent to be sent to the object.
function valueChanged(property, value) {
foreach(selectedObj as obj) {
obj->setProperty(property, value);
}
}
Example
This is an incomplete example to give you my idea about the property system.
I guess SelectableItem * selectedItem must be replaced with a list of items in your case.
class SelectableItem : public QObject
{
Q_OBJECT
Q_PROPERTY(QString name READ name WRITE setName );
Q_PROPERTY(int velocity READ velocity WRITE setVelocity);
public:
QString name() const { return m_name; }
int velocity() const {return m_velocity; }
public slots:
void setName(const QString& name)
{
if(name!=m_name)
{
m_name = name;
emit update();
}
}
void setVelocity(int value)
{
if(value!=m_velocity)
{
m_velocity = value;
emit update();
}
}
signals:
void update();
private:
QString m_name;
int m_velocity;
};
class MyPropertyWatcher : public QObject
{
Q_OBJECT
public:
MyPropertyWatcher(QObject *parent)
: QObject(parent),
m_variantManager(new QtVariantPropertyManager(this)),
m_propertyMap(),
m_selectedItem(),
!m_updatingValues(false)
{
connect(m_variantManager, SIGNAL(valueChanged(QtProperty*, QVariant)), SLOT(valueChanged(QtProperty*,QVariant)));
m_propertyMap[m_variantManager->addProperty(QVariant::String, tr("Name"))] = "name";
m_propertyMap[m_variantManager->addProperty(QVariant::Int, tr("Velocity"))] = "velocity";
// Add mim, max ... to the property
// you could also add all the existing properties of a SelectableItem
// SelectableItem item;
// for(int i=0 ; i!=item.metaObject()->propertyCount(); ++i)
// {
// QMetaProperty metaProperty(item.metaObject()->property(i));
// QtProperty *const property
// = m_variantManager->addProperty(metaProperty.type(), metaProperty.name());
// m_propertyMap[property] = metaProperty.name()
// }
}
void setSelectedItem(SelectableItem * selectedItem)
{
if(m_selectedItem)
{
m_selectedItem->disconnect( this );
}
if(selectedItem)
{
connect(selectedItem, SIGNAL(update()), SLOT(itemUpdated()));
itemUpdated();
}
m_selectedItem = selectedItem;
}
private slots:
void valueChanged(QtProperty *property, const QVariant &value)
{
if(m_updatingValues)
{
return;
}
if(m_selectedItem && m_map)
{
QMap<QtProperty*, QByteArray>::const_iterator i = m_propertyMap.find(property);
if(i!=m_propertyMap.end())
m_selectedItem->setProperty(m_propertyMap[property], value);
}
}
void itemUpdated()
{
m_updatingValues = true;
QMapIterator<QtProperty*, QByteArray> i(m_propertyMap);
while(i.hasNext())
{
m_variantManager->next();
m_variantManager->setValue(
i.key(),
m_selectedItem->property(i.value()));
}
m_updatingValues = false;
}
private:
QtVariantPropertyManager *const m_variantManager;
QMap<QtProperty*, QByteArray> m_propertyMap;
QPointer<SelectableItem> m_selectedItem;
bool m_updatingValues;
};
Calm down, your code has not O(n^2) complextity. You have a nested loop, but only one counts to N (the number of objects), the other counts to a fixed number of properties, which is not related to N. So you have O(N).
For the static variables, you write "there aren't any instance-specific properties", later you write about updates of the individual properties of your objects, which are exactly instance-specific properties. Maybe you are confusing the "class Properties" (which is of course shared among all properties) with the individual properties? So I think you don't need static members at all.
Do you want to display changes to the objects only if they appear, or do you want a continuos display? If your hardware is able to handle the latter, I would recommend going that way. In that case, you have to iterate over all objects anyway and update them along the way.
Edit: The difference is that in the former (update on change) the drawing is initiated by the operation of changing the values, for example a object movement. For the latter, a continuos display, you would add a QTimer, which fires say 60 times a second and calls a SLOT(render()) which does the actual rendering of all objects. Depending on the rate of changes this may actually be faster. And it is probably easier to implement.
Another possibilty is let Qt handle the whole drawing, using a Graphics View, which handles the objects-to-draw internally in a very efficient tree structure. Take a look at
http://doc.trolltech.com/4.5/graphicsview.html
If you want to display only the changes, you could use individual callbacks for each properties value. Each time the value of a property is changed (in this case making the properties vlaues private and using setSomeThing(value)), you call the update function with an emit(update()). If you are absolutly concernd about emit being slow, you could use "real" callbacks via function pointers, but I don't recommend that, Qt's connect/signal/slot is so much easier to use. And the overhead is in most cases really neglible.