Re: nullable

On 27 Aug 2014, at 05:00, Jan-Ivar Bruaroey <jib@mozilla.com> wrote:

> On 8/26/14 9:17 AM, Michael Tuexen wrote:
>> in
>> http://dev.w3.org/2011/webrtc/editor/webrtc.html#rtcpeerconnection-interface-extensions
>> the label argument of createDataChannel() is described as
>> [TreatNullAs=EmptyString] DOMString label
>> I read this that createDataChannel(NULL) is the same as createDataChannel("").
>> Is that correct?
> 
> Yes.Remove [TreatNullAs=EmptyString] and it would be the same as createDataChannel("null"). [1]
Thanks for the clarification.
> 
>> On the other hand, in the table shown in
>> http://dev.w3.org/2011/webrtc/editor/webrtc.html#methods-1
>> it is stated that the label argument is not Nullable. What does this mean?
> 
> WebIDL compilers provide invariants to implementations through generated binding-code, and nullable means the implementation will see and must handle NULL as a discrete value (NULL != "", NULL != 0). Non-nullable means it wont. Nullable is a type-modifier, as a slightly more elaborate type is needed to hold NULL as a distinct value.
> 
>> Isn't that contradicting the above statement?
> 
> No,the binding-code for DOMString label converts NULL into "null" on input, so the implementation never sees or has to deal with NULL.[TreatNullAs=EmptyString] just replaces "null" with "".
> 
> Anullable string would be specified like this: DOMString? label
OK. Thanks.
> 
>> Regarding send() it is stated in
>> http://dev.w3.org/2011/webrtc/editor/webrtc.html#methods-2
>> that the data argument is shown as not Nullable. Does this mean that calling
>> send(NULL) will result in an error/exception?
> 
> While most other types would throw TypeError at you, it seems DOMString always convertsNULL and undefined into a string [2] - likely a gift from javascript.
> 
>>  Does this need to be stated?
> 
> A benefit of using standard webidl is that we don't need to.
OK. Thanks for your quick response!

Best regards
Michael
> 
>> Best regards
>> Michael
> 
> .: Jan-Ivar :.
> 
> [1] http://www.w3.org/TR/WebIDL/#TreatNullAs
> [2] http://www.w3.org/TR/WebIDL/#es-DOMString
> 
> 
>

Received on Wednesday, 27 August 2014 11:43:23 UTC