> Sent from my iPhone

> On 26 Oct 2012, at 05:51, Jørn Wildt <j...@fjeldgruppen.dk> wrote:

> > I have been thinking a bit about this issue and come to the conclusion
> that the HAL approach where rels are indexed in a dictionary has some
> problems. Let me try to explain:

> > To lookup a rel-value, say "printable", a client programmer would do
> like this, since HAL is optimized for the simple/most-used use case:

> >   var url = data._links["printable"].href;

> > But what happens if the server decides to throw in multiple links for
> the same rel-value, for instance both PDF and Word representations of the
> printable stuff? Well, the above code breaks since data._links["printable"]
> would become an array instead of a single value.

> > Now a robust client has to write code like this:

> >   var url = null;
> >   if (data._links["printable"] IS ARRAY)
> >     then lookup in that array
> >   else
> >     select single value.

> > Unfortunately the dictionary approach encourages programmers to write
> the simple client code, assuming there will only be one link for each
> rel-value. This means encouraging programmers to write code that will break
> when the server decides to throw in multiple links for each rel-value.

> > A robust client would always have to write code that somehow respects
> that it may have to traverse an array to find the link it is looking for.
> So why not always use an array like this:

> >   _links : [
> >     { rel="printable", type="pdf", href="..." },
> >     { rel="printable", type="word", href="..." }
> >   ];

> > In that way we encourage (force) client programmers to write code that
> always iterates through the link array - instead of encouraging them to
> write brittle code that will break later on?

> This isn't a big deal. You should obviously avoid churn by getting the
> plurality right first time (usually obvious). In cases where you don't,
> then just treat it like you would any other breaking change - by
> introducing an additional rel. i.e. either pluralize the rel or if you dont
> like plural rels change it some other way and keep it singular.

> Cheers,
> M

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