Okay, so I now understand what is happening a little better.
When I saw a construct like:
bind("example",xhtml,
"first_name" -> SHtml.text(user.first_name, user.first_name(_)),
"last_name" -> SHtml.text(user.last_name, user.last_name(_))
it reminded me of a match with cases and my assumption was that each
match would only be called if and when the match was found. In reality
what appears to happen is that the item on the right hand side of the
"->" is usually evaluated and then placed into a Map with the String
like "first_name" being the key.
So, if every binding is used in every case there is no big issue here,
but if you have bindings that aren't all used they will none-the-less
be evaluated every time you try to bind.
Also every time the bind function is called a new Map appears to be
generated and indexed in memory which doesn't seem as efficient as it
could be.
I can't help but wonder whether this could be converted to a form of
match which would then be built at compile time and re-used and would
only evaluate those matches that matched.
In the meantime I see that you can convert the code above to:
bind("example",xhtml,
FuncBindParam("first_name", () => SHtml.text(user.first_name,
user.first_name(_)),
FuncBindParam("last_name", () => SHtml.text(user.last_name,
user.last_name(_))
to get a form of lazy evaluation.
On Mar 10, 11:01 am, Stuart Roebuck <[email protected]> wrote:
> I've been trying to figure why some binding is giving me a stack
> overflow and I've discovered that if you use the BindHelpers.bind
> method with a set of function BindParams, all the functions are
> evaluated regardless of whether a match is found.
>
> So, for example, if you bind to an empty NodeSeq and have a BindParam
> which will never match like:
> "you won't find me here" -> { print("Got here!");
> NodeSeq.Empty }
> …you find that the print statement is called.
>
> This really surprised me. Is this intentional behaviour as it seems
> to be a potential source of significant redundant processing?
>
> Stuart.
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