W3C home > Mailing lists > Public > public-script-coord@w3.org > April to June 2013

Re: undefined values in dictionaries

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Tue, 11 Jun 2013 23:42:28 -0400
Message-ID: <51B7EE24.3000404@mit.edu>
To: Rik Cabanier <cabanier@gmail.com>
CC: "public-script-coord@w3.org" <public-script-coord@w3.org>
On 6/11/13 11:28 PM, Rik Cabanier wrote:
> You've told me that dictionary members are optional by default [1]. Why
> does their IDL have '?' for most entries? Isn't that implied since every
> entry is optional anyway?

Consider these two dictionaries:

   dictionary Foo1 {
     DOMString member;
   };

   dictionary Foo2 {
     DOMString? member;
   };

and this object being converted to those dictionary types: { member: 
undefined }.

Foo1 will produce { member: "undefined" } while Foo2 will produce { 
member: null }.

Similarly, for { member: null }, Foo1 will produce { member: "null" } 
while Foo2 will produce { member: null }.

This has nothing to do with the fact that having "member" is optional; 
that just affects what happens when an object that does not have a 
"member" property is involved.

-Boris
Received on Wednesday, 12 June 2013 03:42:58 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:37:49 UTC