Note: This is a work in progress and many formatting issues have been fixed. Read more about the project on the home page.

on

The on keyword defines a new message handler of the specified name.

The optional parameterList lets the handler receive values sent along with a message. HyperCard assigns each value to a parameter variable in the parameterList.

Demo Script

Related Topics

• exit
• Handling messages
• param
• paramCount
• params
• pass
• result
• return
• send
• target
• The message-passing order
• Using parameter variables
• What are messages?
• Writing message handlers

Placeholders

messageName

Any text string, without quotation marks, that represents the name of the message handler you want to write:

As in:

parameterList

A comma-separated list of local variable names.

The actual names don’t matter as long as they’re not the same as one of HyperCard’s reserved words. (That is, don’t use result as a variable name.) For example:

statements

Any return-separated list of built-in commands, user-defined handlers, or keywords that are part of a message or function handler.