Hi Tim and all,
really appreciate your patience. Here is the final outcome of my learning
process, with the conclusion that I'll just use Array{MySubType}, i.e. Myt
is kind of redundant. Neverthless, this version here worked - i'll post
that here in the unlikley case someone finds it useful. i don't actually
call the constructor for MySubType, just copy it. So it's really just
getting an array. Anyway, thanks a lot for chipping in!
abstract MyAbstract
type MySubType <: MyAbstract
field1 :: ASCIIString
function MySubType(x)
new(x)
end
end
type Myt{ T<:MyAbstract}
chain :: Array{T,1}
function Myt(n,z::T)
x = [z for i=1:n]
new(x)
end
end
Myt{T}(n::Integer,z::T) = Myt{T}(n,z)
function newType(whichtype,x)
if isa(whichtype,MySubType)
return MySubType(x)
else
println("no other types")
end
end
Myt(3,MySubType("hi"))
Myt{MySubType}([MySubType("hi"),MySubType("hi"),MySubType("hi")])
On Wednesday, 11 June 2014 18:13:04 UTC+1, Tim Holy wrote:
>
> On Wednesday, June 11, 2014 09:34:52 AM Florian Oswald wrote:
> > type MySubType <: MyAbstract
> > field1 :: ASCIIString
> > function MySubType(x)
> > new(x)
> > end
> > end
>
> I would strongly recommend getting rid of the inner constructor. It
> doesn't do
> anything that the default one doesn't do, and you've just caused Julia to
> skip
> creating an outer constructor for you. In most code, inner constructors
> are
> relatively rare and should be provided only if you have a specific need
> for
> them.
>
> > Myt(10,MySubType)
> > ERROR: type: Myt: in T, expected T<:MyAbstract, got Type{DataType}
>
> The interpretation of that error is the following: you're passing z, which
> you
> declare must be an object for which isa(z, MyAbstract) is true. But
> isa(MySubType, MyAbstract) is false. You need to pass an instance (e.g.,
> MySubType("hi")) rather than the type itself.
>
> Once you realize that z must be an instance of type T, you'll quickly
> realize
> that your z("hi") in the inner constructor of Myt is another error. It
> should
> just be z.
>
> As John says, the alternative is to delcare the Myt inner constructor as
> Myt(n,z::Type{T}) and then try to build it as you did. But I doubt that
> will
> give you what you want.
>
> --Tim
>
>
