Named constructors

[Atila Neves]

On Monday, 14 January 2019 at 14:31:09 UTC, aliak wrote:
> On Thursday, 10 January 2019 at 18:27:59 UTC, Atila Neves wrote:
>>> Look at the Builder pattern, it's pretty much a workaround 
>>> for lack of named/keyword arguments.
>>
>> Java doesn't have variadic templates, D does. No builder 
>> pattern needed.
>
> Not sure how variadic templates solves the builder pattern? How 
> do you deal with a mixture of arguments of similar and 
> different types with some being optional and not?
>
> auto a = Builder()
>   .accountNumber(202)
>   .firstName("Bob")
>   .lastName("Who")
>   .branch("N-2")
>   .interest(20.0)
>   .balance(10.0)
>   .build()
>
> ??

auto a = Customer(AccountNumber(202),
                   FirstName("Bob"),
                   LastName("Who"),
                   Branch("N-2"),
                   Interest(20.0),
                   Balance(10.0));

struct Customer {
     this(A...)(auto ref A args) 
if(constraintVerifyingNumberAndTypesOfArgs!A) {
         this.accountNumber = args[staticIndexOf!(AccountNumber, 
A)];
         // etc.
     }
}

If staticIndexOf is negative, assign a default value.


Again, I want to write a library that does this for me based on a 
declaration that looks like a regular function / template.

>> I don't know of any language that does that and has 
>> overloading. Walter knows way more about this than I do.
>
> Swift. Named arguments. Overloading. Executed perfectly IMO:

I can't comment. I don't know anything about Swift.

> Unless he means specifically with using named arguments with 
> any order. Then yeah nah. Swift no can do. But named arguments 
> followed by unnamed and vice versa plus overloading all good.

Probably? I don't really know.