sâmbătă, 5 martie 2016, 22:59:33 UTC+1, Milan Bouchet-Valat a scris:
>
> Le samedi 05 mars 2016 à 13:42 -0800, Adrian Salceanu a écrit :
> > Gentleman, I stumbled onto this one in my code, and despite trying
> > all the possible combinations I could think of, no dice.
> >
> > I have this simple type hierarchy:
> >
> > abstract Model
> > type Package <: Model
> > type Repo <: Model
> >
> > The Model type is an ORM and it defines a series of methods that
> > operate on Model subtypes.
> >
> > ex:
> > function save{T<:Model}(m::T)
> Note that this can be written more simply as:
> function save(m::Model)
>
I noticed that this works too, but I find that the longer syntax better
transmits the notion that the method expects a subtype, rather than the
type itself. Of course, this is lees important in Julia, where the super
type can only be abstract.
>
> (the longer syntax is only useful when T is a parameter of another
> argument type)
>
> > So far so good.
> >
> > Now, according to ORM architecture and design patterns, an instance
> > of a subtype represents a table row, while the class itself
> > represents the table. And of course there are plenty of such
> > methods.
> > For instance, the find_one_by function, which takes the type itself
> > (the table).
> >
> > function find_one_by(m, column_name::SQLColumn, value::SQLInput) #
> > this works, with m::Any
> >
> > The question is, how can I define this method so that it accepts all
> > the types of the subtypes of Model?
> >
> > I tried multiple combinations, such as:
> > function find_one_by{T<:Type{Model}}(m::T, column_name::SQLColumn,
> > value::SQLInput)
> >
> > none was good. :( Any ideas?
> Use this:
> find_one_by{T<:Model}(m::Type{T}, ...
>
>
It works! Wow, awesome! Many thanks!
>
>
> Regards
>
