Right. String was not the right example. AS3 makes all strings
'objects', so they are by default nullable, but Number and Boolean are
not. I expanded your example a little bit:
<canvas debug="true">
<attribute name="values" value="[void 0, null, false, 0,'']" />
<handler name="oninit">
for (var i = 0, l = this.values.length; i < l; i++) { var v =
this.values[i]; this.meth(v, v, v, v); }
</handler>
<method name="meth" args="v, s:String, n:Number, b:Boolean" >
Debug.info("%#w passed as a: String is %#w; Number is %#w;
Boolean is %#w", v, s, n, b);
</method>
</canvas>
Which in swf8/dhtml yields:
INFO: (void 0) passed as a: String is (void 0); Number is (void 0);
Boolean is (void 0)
INFO: null passed as a: String is null; Number is null; Boolean is null
INFO: false passed as a: String is false; Number is false; Boolean is
false
INFO: 0 passed as a: String is 0; Number is 0; Boolean is 0
INFO: '' passed as a: String is ''; Number is ''; Boolean is ''
And in swf9 yields:
INFO: (void 0) passed as a: String is null; Number is NaN; Boolean is
false
INFO: null passed as a: String is null; Number is 0; Boolean is false
INFO: false passed as a: String is 'false'; Number is 0; Boolean is
false
INFO: 0 passed as a: String is '0'; Number is 0; Boolean is false
INFO: '' passed as a: String is ''; Number is 0; Boolean is false
Actually, this is either a compiler bug, or a good doc example... I
think the former. We should make the js1 back-end implement coercions
for types. Hm: http://jira.openlaszlo.org/jira/browse/LPP-5682
On 2009-01-09, at 13:49EST, André Bargull wrote:
Not really...
This testcase prints:
s was null
and _*not*_
s was 'null'
<canvas debug="true" oninit="this.meth(null)" >
<method name="meth" args="s:String" >
Debug.write("s was %w", s);
</method>
</canvas>
The only special thing about Strings in AS3, is how `undefined` is
handled.
var t:String = undefined; // this will be changed to `null`
var r:String = String(undefined); // this is really `undefined`
Finally, you can declare the types of your arguments. These types
are ignored in the JS1 back-ends, but they are enforced in JS2
(swf9).
function foo (required:String, optional:Boolean=false)
Caution: You will get a type error, but _only_ if there is not a
coercion available. Hence, passing `null` as the first argument
to foo above will cause it to be called with the string "null",
not the null value. If you want a nullable type, you should leave
the type undeclared (for now...).
