Beginning AppleScript®

8.10. Labeled Parameters

When you call any of the handlers you defined so far, you have to make sure that you list all the arguments to the handler in the same order that they were listed when you defined the handler. This list of arguments is enclosed within a pair of parentheses and each argument is delimited from the next by a comma. Parameters specified this way are known as positional parameters because their position in the list matters and determines how the arguments are assigned to the corresponding parameters inside the handler.

AppleScript allows you to define and call handlers using a different format that is more like English. It also allows you to specify your arguments in any order. In one form of these so-called labeled parameters, you precede each argument by a chosen label, followed by a colon, followed by the argument. In another form, you precede each argument by a word chosen from a list of prepositions reserved for this purpose. These two forms can be used together, but the syntax starts to get confusing, so you may want to avoid doing that at first.

The next two Try It Out examples show you how to work with the two forms of labeled parameters.

8.10.1.

8.10.1.1. Try It Out: Writing a Handler with Labeled Parameters–Form 1

In this program, you modify your insertItem handler so you can easily remember how to call it. This introduces the first form of labeled parameters.

1. Type the following program into Script Editor:

   on insertItem given theList:L, beforeItem:N, ...