qt - ReferenceError: down is not defined in SpinBox QML -


i referring https://doc.qt.io/qt-5/qtquickcontrols2-customize.html#customizing-spinbox , copy pasted same code, getting following errors:

referenceerror: down not defined , referenceerror: not defined.

code:

import qtquick 2.6 import qtquick.controls 2.1      spinbox {             id: control             value: 50             editable: true              contentitem: textinput {                 z: 2                 text: control.textfromvalue(control.value, control.locale)                  font: control.font                 color: "#21be2b"                 selectioncolor: "#21be2b"                 selectedtextcolor: "#ffffff"                 horizontalalignment: qt.alignhcenter                 verticalalignment: qt.alignvcenter                  readonly: !control.editable                 validator: control.validator                 inputmethodhints: qt.imhformattednumbersonly             }              up.indicator: rectangle {                 x: control.mirrored ? 0 : parent.width - width                 height: parent.height                 implicitwidth: 40                 implicitheight: 40                 color: up.pressed ? "#e4e4e4" : "#f6f6f6"                 border.color: enabled ? "#21be2b" : "#bdbebf"                  text {                     text: "+"                     font.pixelsize: control.font.pixelsize * 2                     color: "#21be2b"                     anchors.fill: parent                     fontsizemode: text.fit                     horizontalalignment: text.alignhcenter                     verticalalignment: text.alignvcenter                 }             }              down.indicator: rectangle {                 x: control.mirrored ? parent.width - width : 0                 height: parent.height                 implicitwidth: 40                 implicitheight: 40                 color: down.pressed ? "#e4e4e4" : "#f6f6f6"                 border.color: enabled ? "#21be2b" : "#bdbebf"                  text {                     text: "-"                     font.pixelsize: control.font.pixelsize * 2                     color: "#21be2b"                     anchors.fill: parent                     fontsizemode: text.fit                     horizontalalignment: text.alignhcenter                     verticalalignment: text.alignvcenter                 }             }              background: rectangle {                 implicitwidth: 140                 border.color: "#bdbebf"             }         }

should include additional imports ?

no, don't need include additional imports. just, example uses bad practice , here see why:

this (reduced modifying up.indicator) code of example:

import qtquick 2.6 import qtquick.controls 2.0  spinbox {     id: control     value: 50     editable: true      up.indicator: rectangle {         x: control.mirrored ? 0 : parent.width - width         height: parent.height         implicitwidth: 40         implicitheight: 40         color: up.pressed ? "#e4e4e4" : "#f6f6f6"  // <---*         border.color: enabled ? "#21be2b" : "#bdbebf"          text {             text: "+"             font.pixelsize: control.font.pixelsize * 2             color: "#21be2b"             anchors.fill: parent             fontsizemode: text.fit             horizontalalignment: text.alignhcenter             verticalalignment: text.alignvcenter         }     } }

here have spinbox root element of file.

now lets talk name resolution.
line in question marked // <---* 

control: up.pressed ? "..." : "..."

where come from? @ first in object, used - rectangle. rectangle has no up-property, continue , looking in root node of file, spinbox - has up-property, has value pressed.

the situation looks different, when try use (the wrong way). let's add applicationwindow:

import qtquick 2.7 import qtquick.window 2.2 import qtquick.controls 2.0  applicationwindow {     id: window      width: 800     height: 600     visible: true      spinbox {         id: control         value: 50         editable: true          up.indicator: rectangle {             x: control.mirrored ? 0 : parent.width - width             height: parent.height             implicitwidth: 40             implicitheight: 40             color: up.pressed ? "#e4e4e4" : "#f6f6f6"             border.color: enabled ? "#21be2b" : "#bdbebf"              text {                 text: "+"                 font.pixelsize: control.font.pixelsize * 2                 color: "#21be2b"                 anchors.fill: parent                 fontsizemode: text.fit                 horizontalalignment: text.alignhcenter                 verticalalignment: text.alignvcenter             }         }     } }

same line - try up in rectangle, fails , continues files root node, applicationwindow. here fails again. applicationwindow not used in file, files root node might exist, search end , fail.

what went wrong? writer of example missed apply practice use qualified identifiers: id.property.... did example define x-value of rectangle.

changing line:

color: up.pressed ? [...]

to:

color: control.up.pressed ? [...]

will solve problem, explicitly declare property up.

important lesson

  • names not resolved going child parent, child files root node , on, until can't go on
  • always identify object either explicitly parent (but aware, might not know parent is. ideally anchors , position) or objects's id

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