Hi,
hope its polite to bump up an old thread like this - if not, please accept
my apologies. I have been struggling with the record update syntax for a
while and wanted to share another use case which I think could be made
better.
So let's say I want to populate a list of objects of the same type which
have a lot of properties, most of which are kept default, e.g.
type alias Customer =
{ id : Int,
Name : String ,
-- Lots of other stuff
}
and I have a "constructor" function to build instances with default values,
but never forget to fill in the id, e.g.
defaultCustomer : Int -> Customer
defaultCustomer id =
{ id = id,
Name = "",
-- lots of other initialization
}
now I would like to write things like
[
{ (defaultCustomer 1) | Name = "Smith" },
{ (defaultCustomer 2) | Name = "Jones" }
]
Which is not possible.
Now I have two options:
a) do not use a "constructor" and always write the records in full (not
nice since they have a lot of fields which are mostly left default)
b) just have a template defaultCostumer : Customer and hope I will never
forget to fill in the id (used in messages)
c) have a long "let" clause before defining the list
Neither of which seems nice.
I'll probably go with b), but if anyone has a nice suggestion how to
enforce filling in a record in this way with the current syntax it would be
very welcome.
And thanks for the work on elm - I am learning it and having fun with it!
Martin
but I tried to figure out where on GitHub should this be discussed and
kind of failed...
(is it https://github.com/elm-lang/elm-plans/issues/16 or
On Saturday, 26 July 2014 18:08:22 UTC+2, Jeff Smits wrote:
>
> Yeah, I really want this feature. But I guess I forgot about the "code
> comparison".
>
> @Evan: can you say more concretely what kind of code comparison you want
> to see before moving forward on this feature?
>
> On Sat, Jul 26, 2014 at 2:26 PM, David Sargeant <[email protected]
> <javascript:>> wrote:
>
>> Seems a little strange that the following does not work:
>>
>> { {} | attrs = [1] }
>>
>> I know it's not really useful, but I guess it goes back to the issue of
>> allowing arbitrary expressions to the left of the vertical bar.
>>
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