before

Type

control structure

Summary

Defines a message handler.

Syntax

before <messageName> [<parametersList>]
   <statementList>
end <messageName>

Description

The before handler is exclusive to behavior scripts and is sent to a behavior script before all messages.

For example, consider a mouseDown message moving through the message path. It gets to an object with a behavior script:

1. The engine looks at the behavior script of the target object - If a

   **before** mouseDown handler is present, it executes it.
2. The engine next looks at the object script - If an on mouseDown
   handler is present, it executes it.
3. The engine now looks at the behavior script - If an after mouseDown
   handler is present, it executes it.
4. The engine finally looks at the object script - If a pass mouseDown
   or no mouseDown handler is present, it moves on to the parent object.

A before handler allows developers to produce behavior scripts which can handle messages sent to a control without having any effect on the message path, unlike front and back scripts.

Parameters

Name	Type	Description
messageName
parametersList
statementList

Examples

before mouseUp
  answer "before mouse up received"
end mouseUp

Related

glossary: message handler

keyword: end, private

command: dispatch

control structure: after, on, exit

function: result, commandNames, paramCount

Compatibility and Support

Introduced

LiveCode 6.0

OS

mac

windows

linux

ios

android

Platforms

desktop

server

mobile