Building applescript records with lists, accessing applescript records with strings
Building applescript records with lists, accessing applescript records with strings
- Subject: Building applescript records with lists, accessing applescript records with strings
- From: Malcolm Fitzgerald <email@hidden>
- Date: Fri, 4 Feb 2005 13:44:08 +1100
Two of the FAQs on this list are, "How do I build an applescript record
from a list?" and "How do I coerce a string to a variable?".
The most frequent answer is "AppleScript is not Perl". However, you can
set a string to a variable using do script and you can build a record
using do script. Do script happily sends strings to the compiler and
returns variables and records.
(* coerce string to variable *)
set theVar to do script ("a reference to " & "x")
--> x (a variable)
(* build an applescript record from strings *)
set theStrings to {"x", "y", "z"}
set theValues to {3, 2, 1}
set s to {}
repeat with i from 1 to (count theStrings)
set s to s & (do script ("{" & item i of theStrings & ":" & item i of
theValues & "}"))
end repeat
--> {x:3, y:2, z:1} (a record)
The problem not that Applescript cannot or doesn't do it. It plainly
does. The problem that AppleScript doesn't make it easy to do.
The most obvious problem is that you cannot access these variables or
records from outside the "do script" unless you can ask them for their
values. To do that you need to ask using their variables. Catch 22!
However, if you're able to pass the query into "do script" at the same
time as you pass the data in you are able to get the results you'd
expect.
The sub-routines below provide a way to use strings and lists as
records. They may appeal to those of you that don't have better ways to
do the same thing.
(*
-- build some data
-- it was Jason Bourque's item pricing problem that started this
set theItemPrices to {}
set theItemLabels to {}
repeat with i from 97 to 122
set end of theItemPrices to i
set end of theItemLabels to ASCII character i
end repeat
*)
-- build the hash
set theHash to BuildHash(theItemLabels, theItemPrices)
-- select a key
set theKey to item (random number from 1 to 27) of theItemLabels -- a
string selected at random
-- example 1
GetHashValue (theKey, theHash)
-- example 2
set priceList to {}
repeat with theVar in theItemLabels
if theVar is in {"j", "m", "t"} then set the end of priceList to
GetHashValue(theVar, theHash)
end repeat
get priceList
--
--
on BuildHash (theKeys, theValues)
-- returns a string which the compiler can cast to a record
set s to {}
repeat with i from 1 to (count theKeys)
set end of s to ","
set end of s to item i of theKeys
set end of s to ":"
set end of s to item i of theValues
end repeat
set s to (rest of s) as string
return "{" & s & "}"
end BuildHash
on GetHashValue (theKey, theHash)
return do script (theKey & " of " & theHash)
end GetHashValue
Malcolm Fitzgerald ph: 02 93180877
Database Manager fax: 02 93180530
The Australian Society of Authors www.asauthors.org
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