using properties in calculations

[mzimmers]

Hi all -

I have a view that uses this code:

Item {
  id: root
  property double cellHeight: <something>
  property double wellSizeRatio: 0.5

  Grid {
    Repeater {
      id: wellsRepeater
      delegate: Rectangle {
        height: cellHeight
        width: height
        color: 'white'
        border.color: 'black'
        Rectangle {
          anchors.centerIn: parent
          height: cellHeight * 0.5
          width: height
          radius: height / 2
        }

This (correctly) produces this:

If I try to replace the hard-coded 0.5 in the Rectangle as follows:

Item {
  id: root
  property double cellHeight: <something>
  property double wellSizeRatio: 0.5

  Grid {
    Repeater {
      id: wellsRepeater
      delegate: Rectangle {
        height: cellHeight
        width: height
        color: 'white'
        border.color: 'black'
        Rectangle {
          anchors.centerIn: parent
          height: cellHeight * wellSizeRatio
          width: height
          radius: height / 2
        }

It doesn't work:

I omitted the derivation of cellHeight, but it works fine (for various sizes). What might I be doing wrong with the wellSizeRatio property?

Thanks...

[fcarney]

@mzimmers said in using properties in calculations:

wellSizeRatio

Is wellSizeRatio italicized in the editor? That would indicate it sees the variable. If no "root" object is not the root of your qml object then you may need to qualify wellSizeRatio like this: root.wellSizeRatio. Does wellSizeRatio get changed anywhere? Try making it a readonly to see if something turns red somewhere.

[mzimmers]

@fcarney your suggestion of making wellSizeRatio readonly led me to find the problem, which was that it was getting overridden in a calling file:

    WellPlate {
      id: theWells
      wellSizeRatio: 0.8 // circle height is smaller than grid square

That's a pretty good debugging tip to keep in mind: if a property seems to be changing out from under you, check the callers for possible "overrides."

Thanks for the help!