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Next, suppose that you decide to install a
Decrement button. You first click the button on the left side
showing the OK-button icon, the one under the button labeled A.
Then, a new set of buttons appears in the adjacent column. You click the OK-button icon in that adjacent column, indicating that you want a labeled button.
At this point, you move the cursor inside the application window, which is
now titled Meter Demonstration. A click, drag, and release produces
a button.
You proceed to replace Button in the Text field with your
preferred label, Decrement.
Next, you move to the When: list box and the Perform: text
field. You select the clicked option from the list box, and type
decrementMeter, without a colon, in the text field. By so doing,
you indicate that you will supply a callback method named
decrementMeter:, with a colon, for the clicked event
associated with the button.
As soon as you supply the method name, an asterisk appears in front of
clicked, which indicates that a callback method name has been
supplied.
All this work leads to the following display:
