AppleScript: The Definitive Guide

Script Properties

A script property (often just called a property) is a script-level global variable with initialization. A script property must be declared, and an initial value must be supplied as part of the declaration. The syntax is:

property propertyName : initialValue

For example:

property x : 5

The abbreviation for property is prop .

A property declaration can appear only at top level or at the top level of a script object. For example:

property x : 5
script myScript
        property y : 10
        -- other stuff
end script
-- other stuff

A property is a variable, so its value can be set and fetched in the normal way. For example:

property x : 10
display dialog x -- 10
set x to 5
display dialog x -- 5

Scoping of Properties

A property is a kind of global variable, and a property declaration has the same downward effect as a global declaration:

property x : 10
script myScript
        display dialog x
end script
on myHandler(  )
        display dialog x
end myHandler
run myScript -- 10
myHandler(  ) -- 10

Both myScript and myHandler can see the property x, because the property declaration works like a global declaration with respect to its downward effects.

The big difference between a global variable and a script property is in the upward effect of their declaration. A property’s scope is confined to the script object where it is declared. The property is automatically visible downwards, as if the property declaration had been a global declaration; but it is not automatically visible anywhere else. Different script ...