How to enumerate the keys and values of a record in AppleScript - json

Question

When I use AppleScript to get the properties of an object, a record is returned.
tell application "iPhoto"
properties of album 1
end tell
==> {id:6.442450942E+9, url:"", name:"Events", class:album, type:smart album, parent:missing value, children:{}}
How can I iterate over the key/value pairs of the returned record so that I don't have to know exactly what keys are in the record?
To clarify the question, I need to enumerate the keys and values because I'd like to write a generic AppleScript routine to convert records and lists into JSON which can then be output by the script.

Answer 1

I know it's an old Q but there are possibilities to access the keys and the values now (10.9+). In 10.9 you need to use Scripting libraries to make this run, in 10.10 you can use the code right inside the Script Editor:
use framework "Foundation"
set testRecord to {a:"aaa", b:"bbb", c:"ccc"}
set objCDictionary to current application's NSDictionary's dictionaryWithDictionary:testRecord
set allKeys to objCDictionary's allKeys()
repeat with theKey in allKeys
log theKey as text
log (objCDictionary's valueForKey:theKey) as text
end repeat
This is no hack or workaround. It just uses the "new" ability to access Objective-C-Objects from AppleScript.
Found this Q during searching for other topics and couldn't resist to answer ;-)
Update to deliver JSON functionality:
Of course we can dive deeper into the Foundation classes and use the NSJSONSerialization object:
use framework "Foundation"
set testRecord to {a:"aaa", b:"bbb", c:"ccc"}
set objCDictionary to current application's NSDictionary's dictionaryWithDictionary:testRecord
set {jsonDictionary, anError} to current application's NSJSONSerialization's dataWithJSONObject:objCDictionary options:(current application's NSJSONWritingPrettyPrinted) |error|:(reference)
if jsonDictionary is missing value then
log "An error occured: " & anError as text
else
log (current application's NSString's alloc()'s initWithData:jsonDictionary encoding:(current application's NSUTF8StringEncoding)) as text
end if
Have fun, Michael / Hamburg

Answer 2

If you just want to iterate through the values of the record, you could do something like this:
tell application "iPhoto"
repeat with value in (properties of album 1) as list
log value
end repeat
end tell
But it's not very clear to me what you really want to achieve.

Answer 3

Basically, what AtomicToothbrush and foo said. AppleScript records are more like C structs, with a known list of labels, than like an associative array, with arbitrary keys, and there is no (decent) in-language way to introspect the labels on a record. (And even if there were, you’d still have the problem of applying them to get values.)
In most cases, the answer is “use an associative array library instead.” However, you’re specifically interested in the labels from a properties value, which means we need a hack. The usual one is to force an error using the record, and then parse the error message, something like this:
set x to {a:1, b:2}
try
myRecord as string
on error message e
-- e will be the string “Can’t make {a:1, b:2} into type string”
end
Parsing this, and especially parsing this while allowing for non-English locales, is left as an exercise for the reader.

Answer 4

ShooTerKo's answer is incredibly helpful to me.
I'll bring up another possibility I'm surprised I didn't see anyone else mention, though. I have to go between AppleScript and JSON a lot in my scripts, and if you can install software on the computers that need to run the script, then I highly recommend JSONHelper to basically make the whole problem go away:
https://github.com/isair/JSONHelper