AppleScript: The Definitive Guide, 2nd Edition

List Coercions

Anything may be coerced to a list . How it is treated depends on what you start with:

A list

The result is identically the same list.

A record

The result is a list of the values from the record:

set R to {name:"Matt", age:51}
R as list -- {"Matt", 51}

Anything else

The result is a list of one item, that item being the thing you started with.

Coercion to a list is very useful for making sure you have a list; if the thing you start with isn't a list, it becomes one, and if it is a list, it is unchanged. Recall, however, that this coercion might not work if the thing you start with belongs to an application, because that application might not implement it (see "Coercion by a Scriptable Application," earlier in this chapter).

Officially you can't coerce a list to a record, but there's a trick for doing it using a second level of evaluation. (Consider the warnings at "Second-Level Evaluation" in Chapter 19 before resorting to this trick; it involves a lot of overhead.) The value of every odd item of the list (which should be a string) becomes the name of a record item, whose value in turn is the corresponding even item of the list:

on listToRecord(L)
    script myScript
        return {«class usrf»:L}
    end script
    return run script myScript
end listToRecord
set R to listToRecord({"name", "haha", "age", 51})
R -- {|name|:"haha", age:51}

To understand the trickery involved here, see "Record" in Chapter 13. Observe that because we are forming a user record, the term name ends up in pipes; ...