On Dec 24, 2010, at 9:38 PM, Garrett Smith wrote:
> On 12/24/10, Michael Haufe (TNO) <t...@thenewobjective.com> wrote:
>> On Dec 24, 6:43 pm, Garrett Smith <dhtmlkitc...@gmail.com> wrote:
>>> The client of the API gets an interface object that has properties and
>>> methods so instanceof and constructor shouldn't matter.
>>
>> instanceof is important for an interface consumer to be certain that
>> they are using the proper object:
>>
> I disagree.
>
>> function draw(group){
>> if(group instanceof Group){
>
> If the program is written so that group then it won't matter. The
> program can be safe enough to not have to worry about that. Example:
>
> var group = createGroup();
> draw(group);
>
> The program would be clear what `group can do at that point. The
> constructor or prototype wouldn't matter; what matters at that point
> is what `group` can do.
>
> But if you're not sure at any point, then sure, you can use
> inferential tests like this:
>
>> if(typeof group == "object" && typeof group.method1 == "function"
>> && typeof group.method2 == "function"
>> && typeof group.method3 == "function"){
>> //well, it looks like a group....
>
> I don't like to see all that into an inline block. It is much less
> cluttered if the typechecking is moved into a separate function, such
> as:
>
> if(Group.isGroupLike(group)) {
>> group.method1();
>> group.method2();
>> group.method3(); //oops, its not the droid you're looking for
>> } else {
>> throw new Error("Shape Group Expected");
>> }
>> }
>>
> Better yet just get rid of the typechecking there.
>
> But, when I want to use instanceof, which is rarely, it is inside scope.
>
> For example, in domunit, there is a catch block that catches what
> might be any of: A thrown custom error (EarlyExit or Wait), or a
> runtime test error. EarlyExit and Wait are in the same scope so they
> can't be coming from another frame and instanceof can work there.
> --
> Garrett
so you always check your types in your factories?
and always check for the interface on your apis?
is this efficient?
so the draw method should draw anything that complies with the interface? how
many mutations of objects do you have that could not be written as extensions
or objects?
is this mutations so big to check the interface every time (this will mean that
you don't even know how your code is behaving to check the api of the object)?
how about check for drawable type.
do you really code like you code in the emails? or can you send a real code
when the examples you provide are necessary?
>
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