updating elements in a repeater?

kshegunov

@mzimmers said in updating elements in a repeater?:

Do I have to convert Bottle from a struct to a C++ class?

No, but you can't keep the objects in a QVariantList, because QObjects can't be copied. You need to switch to QList<QObject *>.

PS.
Additional notes:

The notifier signals should report the new value of the property (look up the documentation examples).
If you need to compare floats, then you should probably stick to defining your own setters and getters and registering them with READ/WRITE in the Q_PROPERTY definition instead of relying on MEMBER.

mzimmers

@kshegunov said in updating elements in a repeater?:

No, but you can't keep the objects in a QVariantList, because QObjects can't be copied.

I must be going crazy, but...where in my struct am I using QVariantList?

Thanks for the note about including the new values in the signals.

I'm avoiding floats for the reason you cited, plus a couple more.

kshegunov

@mzimmers said in updating elements in a repeater?:

I must be going crazy, but...where in my struct am I using QVariantList?

Nowhere, but how do you marshal the objects to QML?

mzimmers

@kshegunov said in updating elements in a repeater?:

@mzimmers said in updating elements in a repeater?:

I must be going crazy, but...where in my struct am I using QVariantList?

Nowhere, but how do you marshal the objects to QML?

Well, like this (I think this is what you're asking):

    Column {
      id: myColumn
      Repeater {
        id: bottleRepeater
        model: bottleModel
        Bottle {
          cellX: model.x
          cellY: model.y
          cellHeight: model.height
          cellWidth: model.width
          volume: model.volume
          bottleScaleFactor: scaleFactor
        }

But if I'm doing something wrong in QML, why is the compiler giving me an error pointed at my struct?

kshegunov

@mzimmers said in updating elements in a repeater?:

Well, like this (I think this is what you're asking):

I mean from the C++ side. What is bottleModel and where does it come from?

mzimmers

From the same QML file:

  ListModel {
    id: bottleModel

    ListElement {
      // position 1
      x: 400
      y: 17
      height: 75
      width: 75
    }
    ...

kshegunov

This is confusing, I thought the data is supposed to come from C++.

mzimmers

I know, I'm doing a lousy job of explaining this. in C++:

typedef QVector<Bottle> Bottles;
class ReagentManager : public QObject {
  Q_OBJECT
 private:
  Bottles m_bottleList;
}
<in another file>
  ReagentManager m_reagentManager;
  engine->rootContext()->setContextProperty("reagentManager", &m_reagentManager);

In QML:

    onVisibleChanged: {
      if (visible) {
        reagentManager.updateBottleList()
        rack.updateBottles()
      }
    }

    // update our QML array based on the C++ model.
    function updateBottles() {
      var modelSize = bottleModel.count
      var i
      var l_color
      var volume
      var minVolume
      var amountNeeded
      var name

      for (i = 0; i < modelSize; ++i) {
        name = reagentManager.getName(i)
        bottleRepeater.itemAt(i).cellText = name

        volume = reagentManager.m_volume
        minVolume = reagentManager.getMinVolume(i)
        amountNeeded = reagentManager.getAmountNeeded(i)
        l_color = ((volume - minVolume) >= amountNeeded) ? "green" : "red"
        bottleRepeater.itemAt(i).cellColor = l_color
      }
    }

So, my QML function calls C++ routines to obtain the needed data. I'm trying to convert this to the approach you suggested; this is where I ran into the problem with the struct.

I still don't see where the QVariantList comes into play, though.

kshegunov

typedef QVector<Bottle> Bottles;

If Bottle is derived from QObject you can't keep it directly in a vector (can't copy the objects). You need to keep Bottle * there.

mzimmers

@kshegunov ah. OK, thanks for that. I'll look into making that change, and will report back.

mzimmers

I've changed my QVector to pointers (seems to be working).

I think I see why my example is so confusing -- in my Bottle Repeater, I'm using a QML ListModel. This ListModel only contains UI-specific information (position, size). Additional informationmust come from an object (ReagentManager) that is exposed via a call to setContextProperty().

So: do I need to change my model to the instance of ReagentManager, and find another way to access the information currently in my ListModel? Or is there a more clever way to do this?

Thanks...

kshegunov

@mzimmers said in updating elements in a repeater?:

So: do I need to change my model to the instance of ReagentManager, and find another way to access the information currently in my ListModel? Or is there a more clever way to do this?

Why do you need the ListModel is the question now. Pass the objects vector from the context property (i.e the bottleManager object) directly to the repeater.

mzimmers

@kshegunov said in updating elements in a repeater?:

Why do you need the ListModel is the question now. Pass the objects vector from the context property (i.e the bottleManager object) directly to the repeater.

I'm using the list model for UI-specific information:

  ListModel {
    id: bottleModel

    ListElement {
      // position 1
      x: 400
      y: 17
      height: 75
      width: 75
    }
    ...

I could probably put this data in arrays in QML. As I mentioned, I'd prefer not to put it into my C++ as it's purely UI data.

From my definition of the ReagentManager class:

class ReagentManager : public QObject {
  Q_OBJECT
 public:
  explicit ReagentManager(QObject *parent = nullptr);
  Bottles m_bottleList;
  Q_PROPERTY(Bottles bottleList MEMBER m_bottleList)
  ...

And in my QML:

    function updateBottles() {
      var modelSize = bottleModel.count
      var i
      var volume

      for (i = 0; i < modelSize; ++i) {
        volume = reagentManager.bottleList[i].volume
    ...

I'm getting an error "TypeError: Cannot read property '0' of undefined." Is my syntax wrong, or am I still not understanding how to access the property?

Thanks...

EDIT: looking at the QML Debugger Console, I see this message:

QMetaProperty::read: Unable to handle unregistered datatype 'Bottles' for property 'ReagentManager::bottleList'

kshegunov

@mzimmers said in updating elements in a repeater?:

I could probably put this data in arrays in QML. As I mentioned, I'd prefer not to put it into my C++ as it's purely UI data.

You already have this data in the c++, you feed it to the JS engine as far as I can see. I'd just tie the cpp backend to the UI stuff and not mess with any intermediate stuff, much less using explicit JS code.

Basically like this:

Column {
      Repeater {
        model: reagentManager.bottleList //< This being a property that holds the list of bottles
        Bottle {
          cellX: modelData.x
          cellY: modelData.y //< Or use some other value, or nothing, however you decide to do it
          ...
          volume: modelData.volume //< This binds to the property of the QObject, so when the C++ changes value this updates
          ...
        }
     ...
}

@mzimmers said in updating elements in a repeater?:

I'm getting an error "TypeError: Cannot read property '0' of undefined." Is my syntax wrong, or am I still not understanding how to access the property?
Thanks...
EDIT: looking at the QML Debugger Console, I see this message:

From the method:

https://doc.qt.io/qt-5/qqmllistproperty.html
or
you return QList<QObject *>
or
you return a QVariantList() << bottle1 << bottle2

... different possibilities.

mzimmers

I've changed my typedef from a QVector to a QList:

typedef QList<Bottle *> Bottles;

My C++ looks like this (stripped down) now:

struct Bottle : public QObject {
  Q_OBJECT
  Q_PROPERTY(quint32 volume MEMBER m_volume)
 public:
  quint32 m_volume;                // amount in bottle (in uL)
 signals:
  void volumeChanged(quint32 m_volume);
};
typedef QList<Bottle *> Bottles;

class ReagentManager : public QObject {
  Q_OBJECT
 private:
  Bottles m_bottleList;
 public:
  Q_INVOKABLE Bottles bottleList() { return m_bottleList; }
  void bottleListChanged();
};

And this line in QML:

        volume = reagentManager.bottleList[i].volume

Now produces this error:

qrc:/qml/Rack.qml:194: TypeError: Cannot read property 'volume' of undefined

So...I've kicked the can a little further down the street, but I'm not home yet. It seems that the QML can now access the QList (agree?), but not its properties. Do I need a getter for this? I thought the idea of getting the properties working properly was to eliminate the need for the getters/setters.

ODБOï

@mzimmers said in updating elements in a repeater?:

volume = reagentManager.bottleList[i].volume

bottleList is a function but you are accessing like an array

volume = reagentManager.bottleList()[i]

mzimmers

@LeLev said in updating elements in a repeater?:

@mzimmers said in updating elements in a repeater?:

volume = reagentManager.bottleList[i].volume

bottleList is a function but you are accessing like an array

volume = reagentManager.bottleList()[i]

Thanks...I thought this would work:

 volume = reagentManager.bottleList()[i].volume

But I get this error:

Error: Unknown method return type: Bottles

This goes back to what kshegunov was talking about earlier, but I thought I'd fixed this by changing from a QVector to a QList:

typedef QList<Bottle *> Bottles;

class ReagentManager : public QObject {
  Q_OBJECT
 public:
  Q_INVOKABLE Bottles bottleList() { return m_bottleList; }

I'm still missing something...

ODБOï

@mzimmers said in updating elements in a repeater?:

I'm still missing something...

i would return a QVariantList to qml instead of the QList<Bottle *>

mzimmers

@LeLev OK, but...how do I do that? I can't just cast it. Do I have to change my Bottles typedef?

Thanks...

ODБOï

Q_INVOKABLE QVariant bottleList() { return QVariant::fromValue(m_bottleList); }