859: Mainline

Recall now that the meter is a viewer of a value holder, as established by the method defined in Segment 849. Accordingly, to get at the value to be displayed, the displayOn: method sends the model message to self, fetching the value in the model instance variable. Then, as it does with all value holders, the value message gets the value:

MeterDemonstration method definition • instance 
displayOn: thePen 
  | ... modelValue ... | 
  ... 
  modelValue := self model value. 
  ...