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Change in a model is typically initiated by a button click or key press
observed by a controller. The following illustrates such a button click or
key press by employing a method that simulates a button click, rather than a real button click. Each time that a
click is simulated, the x instance variable in the model is
incremented by way of the setter, setX, which initiates the
changed:–update: sequence that leads to display by the
viewer:
ControllerSubclass method definition • instance simulateClick Transcript show: 'Button click simulated'; cr. self model setX: (self model getX + 1). Workspace C := ControllerSubclass new. C model: M. C simulateClick. C simulateClick. C simulateClick. Transcript Button click simulated Sample viewer responding to #x update message Model x value, determined in viewer, is 1 Button click simulated Sample viewer responding to #x update message Model x value, determined in viewer, is 2 Button click simulated Sample viewer responding to #x update message Model x value, determined in viewer, is 3
In the click simulation, and the resulting action, you see activity analogous to that shown graphically in Segment 791.