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Thread: property binding in a repeater

  1. 22nd March 2015, 11:10 #1
    sedi
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    Question property binding in a repeater

    Hi,
    I have an item with 12 text fields, laid out as a grid and produced with a repeater.
    Now I want to make bindings to one property each (line 29). How can I do that elegantly?

    I don't even know which words to use for a google search on this...
    I can imagine it might be possible with some kind of list in the property section?

    Here's a condensed code that should clarify what I mean:

    Qt Code: 
    1. import QtQuick 2.2
    2. import QtQuick.Controls 1.1
    3.  
    4. Item {
    5.  
    6.     id: personButtonBasis
    7.  
    8.     property string data00Text: ""
    9.     property string data01Text: ""
    10.     property string data02Text: ""
    11.     property string data03Text: ""
    12.     property string data04Text: ""
    13.     property string data05Text: ""
    14.     property string data06Text: ""
    15.     property string data07Text: ""
    16.     property string data08Text: ""
    17.     property string data09Text: ""
    18.     property string data10Text: ""
    19.     property string data11Text: ""
    20.  
    21.  
    22.     Grid {
    23.         id: dataTextGrid
    24.         columns: 3
    25.         Repeater {
    26.             id: dataFieldRepeater
    27.             model:12
    28.             Text {
    29.                 text: ???????????
    30.             }
    31.         }
    32.  
    33. }
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    I tried in vain to "compose" the property name as in this (non-working) example (located starting from line 29):
    Qt Code: 
    1. Binding {
    2.                     target: personButtonBasis;
    3.                     property: (index<10)? "data0%1Text".arg(index) : "data%1Text".arg(index)
    4.                     value: text
    5.                 }
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    It might well be a very stupid question, as I am still very new to the QML world.
    Last edited by sedi; 22nd March 2015 at 13:56.
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  2. 23rd March 2015, 09:54 #2
    joko
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    Default Re: property binding in a repeater

    I think you need to implement it using ListModel

    Qt Code: 
    1. Item { 
    2.     id: personButtonBasis
    3.  
    4.     ListModel {
    5.       id: buttonModel
    6.       ListElement {
    7.         text: "Button 1"
    8.       }
    9.       ListElement {
    10.         text: "Button 2"
    11.       }
    12.       ListElement {
    13.         text: "Button 3"
    14.       }
    15.       ListElement {
    16.         text: "Button 4"
    17.       }      
    18.     }
    19.  
    20.  
    21.     Grid {
    22.         id: dataTextGrid
    23.         columns: 3
    24.         Repeater {
    25.             id: dataFieldRepeater
    26.             model: buttonModel
    27.             Text {
    28.                 text: model.text
    29.             }
    30.         } 
    31.     }
    32. }
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    sedi (23rd March 2015)
  4. 23rd March 2015, 10:11 #3
    anda_skoa
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    Default Re: property binding in a repeater

    What you would usually do in such a situation is to have a model instead of all these string properties.

    In the easiest case the model would just be a list of strings

    Qt Code: 
    1. Item {
    2.     property var texts: [ "a", "b", c" ]
    3.  
    4.     Repeater {
    5.         model: parent.texts
    6.  
    7.         Text {
    8.             text: modelData
    9.         }
    10.     }
    11. }
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    Cheers,
    _
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    sedi (23rd March 2015)
  6. 1st April 2015, 11:41 #4
    sedi
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    Red face Re: property binding in a repeater [SOLVED]

    Thanks, anda_skoa!
    That's exactly what I did - and it works! I have a rather complex model with several lists in it and it was not easy to get it done, but here are a few details for others with the same problem. This is not a compileable example (too big), it may have been shortened too much and may contain simplification mistakes - but it might perhaps be able to shorten the solution finding process of others anyway.

    I need several buttons, each with several data fields on it. The latter are defined here:
    Qt Code: 
    1. class DataFieldContent: public QObject
    2. {
    3.     Q_OBJECT
    4.     Q_PROPERTY(QString text READ text WRITE setText NOTIFY textChanged)
    5.     Q_PROPERTY(QColor color READ color WRITE setColor NOTIFY colorChanged)
    6. signals:
    7.     void textChanged();
    8.     void colorChanged();
    9. public:
    10.     [...]
    11.  
    12.     //getters
    13.     QString text();
    14.     QColor color();
    15.  
    16.     //setters
    17.     void setText(QString text);
    18.     void setColor(QColor color);
    19. };
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    All my data fields are organized in a C++ class "Content":
    Qt Code: 
    1. class Content: public QObject
    2. {
    3.     Q_OBJECT
    4.     Q_PROPERTY(QQmlListProperty<DataFieldContent>dataFieldContents  READ dataFieldContents NOTIFY dataFieldContentsChanged)
    5.  
    6. signals:
    7.     void dataFieldContentsChanged();
    8. public:
    9. 	[...]
    10. 	QQmlListProperty<DataFieldContent> dataFieldContents() { return 
    11. 		QQmlListProperty<DataFieldContent> (this,
    12. 											0,
    13. 											&appendDataFieldContent,
    14. 											&dataFieldContentsCount,
    15. 											&dataFieldContentAt,
    16. 											&dataFieldContentsClear); 
    17. 	}
    18.  
    19.     static void appendDataFieldContent(QQmlListProperty<DataFieldContent> *list, DataFieldContent *p);
    20.     static int dataFieldContentsCount(QQmlListProperty<DataFieldContent> *list);
    21.     static DataFieldContent* dataFieldContentAt(QQmlListProperty<DataFieldContent> *list, int i);
    22.     static void dataFieldContentsClear(QQmlListProperty<DataFieldContent> *list);
    23.  
    24. protected:
    25.     QList<DataFieldContent*>m_dataFieldContents;
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    As I need a bunch of those Buttons, there is also a GroupContent, basically a List of Contents (Note that QList does not derive from QObject, you can't "just use" it).

    Qt Code: 
    1. class GroupContent: public QObject
    2. {
    3.     Q_OBJECT
    4.     Q_PROPERTY(QQmlListProperty<Content> contents READ contents NOTIFY contentsChanged)
    5.  
    6. signals:
    7.     void contentsChanged();
    8. public slots:
    9.     void contentsChangedSlot();
    10.  
    11. public:
    12. 	[...]
    13.     QQmlListProperty <Content> contents();
    14.  
    15.     static void appendContent(QQmlListProperty<Content> *list, Content *p);
    16.     static int contentsCount(QQmlListProperty<Content>*list);
    17.     static Content* contentAt(QQmlListProperty<Content> *list, int i);
    18.     static void contentsClear(QQmlListProperty<Content> *list);
    19.  
    20.     void addContent(Content* p) { m_Contents.append(p);}
    21.  
    22.  
    23. protected:
    24.     QList<Content*> m_Contents;
    25. };
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    On the QML side we need a display: MyButton.qml:

    Qt Code: 
    1. Item {
    2.     id: ButtonBasis
    3.     property var dataFields;
    4.  
    5. 	Grid {
    6. 			[...]
    7. 			Repeater {
    8. 				id: dataFieldRepeater
    9. 				model: ButtonBasis.dataFields
    10. 				Text {
    11. 					text: dataFieldRepeater.model[index].text
    12. 					color: dataFieldRepeater.model[index].color
    13. 					[...]
    14.  
    15. 				}
    16. 			}
    17. 	}
    18. }
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    And all that is linked together in main.qml:

    Qt Code: 
    1. Repeater {
    2.         id: contentRepeater
    3.         model: groupContent.contents
    4.         delegate: MyButton {
    5.             dataFields: contentRepeater.model[index].dataFieldContents
    6. 			[...]
    7.         }
    8.     }
    To copy to clipboard, switch view to plain text mode 

    Don't forget to register your classes to QML (e.g. in main.cpp) by:

    Qt Code: 
    1. qmlRegisterType<DataFieldContent>("de.yourdomain.whatsoever.whatsoever",2,0,"DataFieldContent");
    2. qmlRegisterType<Content>("de.yourdomain.whatsoever.whatsoever",2,0,"Content");
    3. qmlRegisterType<GroupContent>("de.yourdomain.whatsoever.whatsoever",2,0,"GroupContent");
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  7. 1st April 2015, 15:10 #5
    anda_skoa
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    Default Re: property binding in a repeater [SOLVED]

    Inside a delegate you can always address the current data entry like this

    Qt Code: 
    1. model.property
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    E.g. in your case
    Qt Code: 
    1. text: model.text
    2. color: model.color
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    Cheers,
    _
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    sedi (2nd April 2015)
  9. 2nd April 2015, 00:31 #6
    sedi
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    Default Re: property binding in a repeater [SOLVED]

    You are right, of course. Normally that should be the easier solution. I have, although, tried that in vain before - probably the problem was my use of nested delegates - so "model" had to be specifically addressed.
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  10. 2nd April 2015, 08:45 #7
    anda_skoa
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    Default Re: property binding in a repeater [SOLVED]

    In such a case I would suggest keeping the data locally referencable instead

    Qt Code: 
    1. delegate: Item {
    2.     id: delegateRoot
    3.     readonly property text: model.text
    4.  
    5.     Text {
    6.         text: delegateRoot.text // or here also: parent.text
    7.     }
    8. }
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    That way you can potentially use the delegate in other views, referencing the model through a named view binds it to that specific view instance (can't even rename the view without breaking the delegate!)

    Cheers,
    _
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