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  1. Qt
  2. QTBUG-89300

Objects that still remain referenced are recycled by QJSEngine

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    • Platform/s:
      macOS

      Description

      Hi, 

      The attachment is the demo code.

      The JSONObj and JSONArray is derived from QObject and registered into JSEngine by 

      // code placeholder
      
          QJSValue jsonObj = engine.newQMetaObject(&JSONObj::staticMetaObject);
          engine.globalObject().setProperty("JSONObj", jsonObj);
      
          QJSValue jsonary = engine.newQMetaObject(&JSONArray::staticMetaObject);
          engine.globalObject().setProperty("JSONArray", jsonary);
      
      

      Below is the QML code. I print the first element in the array each time add a new element, but after about 800 times adding, the first element is recycled by the engine, and I can not print it any more . The first element is referenced by the  "mainary", I want to know why it is recycled. Thank you!

       

      // code placeholder
       MouseArea{
                  anchors.fill: parent
                  onClicked: {
                      var mainary = new JSONArray();
                      for(var ii=0;ii<2000;ii++)
                      {
                          var ary = new JSONArray();
                          for(var i =0;i<2;i++)
                          {
                              var obj = new JSONObj();
                              obj.put("name","qt_company "+ii+" "+i)
      //                        obj.put("name","qt_company ")
                              ary.add(obj)
          //                    console.log("index "+i+" print first element: "+ary.get(0).get("name"))
                          }
      //                    console.log("array lenghth "+ary.size())
                          mainary.add(ary);
                          console.log("index : "+ii+ " print first element :"+mainary.get(0).get(0).get("name"))
                      }
      
      
                  }
              }
      

       

      Log:

      // code placeholder
      qml: index : 848 print first element :qt_company 0 0
      qml: index : 849 print first element :qt_company 0 0
      qml: index : 850 print first element :qt_company 0 0
      qml: index : 851 print first element :qt_company 0 0
      qml: index : 852 print first element :qt_company 0 0
      qml: index : 853 print first element :qt_company 0 0
      qml: index : 854 print first element :qt_company 0 0
      qrc:/main.qml:30: TypeError: Cannot call method 'get' of null
      

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            Assignee:
            qt.team.quick.subscriptions Qt Quick and Widgets Team
            Reporter:
            yorkchenqt1989 York Chen
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              Dates

              Created:
              Updated:
              Resolved:

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