before

Defines a message handler.

# Metadata

Platforms: desktop, server, mobile OS: mac, windows, linux, ios, android Introduced: 6.0 Security:

# Syntax

before messageName [parametersList] statementList end messageName

# Params

- messageName : - parametersList : - statementList :

# Examples

before mouseUp answer "before mouse up received" end mouseUp

# 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.

# Tags

# See

- **keyword:** end, private - **command:** dispatch - **function:** result, commandNames, paramCount - **control structure:** after, on, exit - **glossary:** message handler