.. or depending on your wider context, if you don't want the
customerDefaults value polluting your namespace:
customers =
let
customerDefaults = { name = "", height = 0.0 }
in
[ newCustomer 1 { customerDefaults | name = "Bill" }
...
]
On Wed, Sep 14, 2016 at 5:29 PM, Jaap Bouma <[email protected]> wrote:
> How about this:
>
> type alias Customer =
> { id : Int
> , name : String
> , height: Float
> }
>
> customerDefaults = { name = "", height = 0.0 }
>
> newCustomer : Int -> { a | name: String, height: Float } -> Customer
> newCustomer id opts =
> { id = id
> , name = opts.name
> , height = opts.height
> }
>
> customers =
> [ newCustomer 1 { customerDefaults | name = "Bill" }
> , newCustomer 2 { customerDefaults | height = 2.0 }
> ]
>
> On Wed, Sep 14, 2016 at 4:41 PM, Martin Cerny <[email protected]> wrote:
>
>> The pipe solution seems OKish - thanks for the suggestion!
>>
>> Martin
>>
>> On Tuesday, 13 September 2016 20:03:14 UTC+2, Nick H wrote:
>>>
>>> Another solution might be to define some setters, so that you could
>>> write something like:
>>>
>>> [
>>> defaultCustomer 1 |> setName "Smith" |> setOccupation |> "Clerk",
>>> defaultCustomer 2 |> setName "Jones",
>>> defaultCustomer 3 |> setNickname "R2-D2" |> setHeight 0.5
>>> ]
>>>
>>>
>>> Unfortunately, defining all those setters is verbose. But I often find
>>> them much nicer to work with than Elm's record-updating syntax.
>>>
>>> I am willing to jump through a lot of hoops in order to use pipe
>>> operators :-)
>>>
>>>
>>> On Tue, Sep 13, 2016 at 10:49 AM, Nick H <[email protected]> wrote:
>>>
>>>> OK, this is a more complex issue than what I had in mind. If you have a
>>>> small number of desired initializations (maybe 2 or 3 cases besides
>>>> defaultCustomer), I think it would make sense to have multiple construction
>>>> functions. But of course that won't scale at all.
>>>>
>>>>
>>>> On Tue, Sep 13, 2016 at 7:03 AM, Martin Cerny <[email protected]> wrote:
>>>>
>>>>> Hi,
>>>>> thanks for the suggestion, but I think you are answering to a
>>>>> different problem than the one I had in mind, I'll try to be more clear to
>>>>> avoid confusion.
>>>>> In my use case, I have a lot of fields, which usually can be kept with
>>>>> their default values, but some of them aren't. So not all customers need
>>>>> names. Maybe a better example of the code I want to write would be:
>>>>>
>>>>> type alias Customer =
>>>>> { id : Int,
>>>>> name : String ,
>>>>> occupation : String,
>>>>> nickname : String,
>>>>> height : Float,
>>>>> -- Lots of other stuff
>>>>> }
>>>>>
>>>>>
>>>>> defaultCustomer : Int -> Customer
>>>>> defaultCustomer id =
>>>>> { id = id,
>>>>> name = "",
>>>>> occupation = "",
>>>>> nickname "N/A",
>>>>> height : 1.6,
>>>>> -- lots of other initialization
>>>>> }
>>>>>
>>>>> [
>>>>> { (defaultCustomer 1) | name = "Smith", occupation = "Clerk" },
>>>>> { (defaultCustomer 2) | name = "Jones" }
>>>>> { (defaultCustomer 3) | nickname = "R2-D2", height = 0.5 }
>>>>> ]
>>>>>
>>>>>
>>>>>
>>>>> Martin
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Monday, 12 September 2016 17:50:21 UTC+2, Nick H wrote:
>>>>>>
>>>>>> In this case, I think the best thing to do would be to make a
>>>>>> construction function that takes a name as well as an id.
>>>>>>
>>>>>> defaultCustomer : Int -> String -> Customer
>>>>>> defaultCustomer id name =
>>>>>> { id = id,
>>>>>> , name = name,
>>>>>> -- lots of other initialization
>>>>>> }
>>>>>>
>>>>>> You constructor function should never return an incomplete/invalid
>>>>>> record. If your customers always need names, make sure they always get
>>>>>> names!
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Sun, Sep 11, 2016 at 4:44 AM, Martin Cerny <[email protected]>
>>>>>> wrote:
>>>>>>
>>>>>>> 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]> 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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>>>>>>>>> Groups "Elm Discuss" group.
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>>>>>>>>> send an email to [email protected].
>>>>>>>>> For more options, visit https://groups.google.com/d/optout.
>>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>> You received this message because you are subscribed to the Google
>>>>>>> Groups "Elm Discuss" group.
>>>>>>> To unsubscribe from this group and stop receiving emails from it,
>>>>>>> send an email to [email protected].
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>>>>>>>
>>>>>>
>>>>>> --
>>>>> You received this message because you are subscribed to the Google
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>>>>> an email to [email protected].
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>>>>>
>>>>
>>>>
>>> --
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>>
>
>
>
> --
> Jaap Bouma
> Oosterstraat 9
> 8011 GM Zwolle
> 06 2951 2694
>
--
Jaap Bouma
Oosterstraat 9
8011 GM Zwolle
06 2951 2694
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