Le dimanche 21 février 2016 à 07:30 -0800, Tomas Lycken a écrit :
> In a package, I have a method foos which currently returns a
> collection of Bars. This is a little unfortunate, so I would like to
> instead return a value of type FooCollection on which I can call the
> bar function to get the array of Bars. I can get backwards
> compatibility by making FooCollection iterable, by implementing
> start, next and done. Now, I have the following:
>
> immutable Bar end
> immutable FooCollection
> bars::Vector{Bar}
> end
>
> foos() = FooCollection(Bar[])
> bars(fc::FooCollection) = fc.bars
>
> start(fc::FooCollection) = start(fc.bars)
> next(fc::FooCollection, state) = next(fc.bars, state)
> done(fc::FooCollection, state) = done(fc.bars, state)
> This works - both the new and the old api:s are supported, and they
> do the right thing.
>
> Next, I’d like to deprecate iteration on FooCollection, to make it
> obvious to users that although their code isn’t broken, they’re
> relying on an API that might not work forever. Instead of for bar in
> foos() I want them to write for bar in bars(foos()). Thus, I make the
> following changes to the iteration protocol:
>
> @deprecate start(fc::FooCollection) start(bars(fc))
> @deprecate next(fc::FooCollection, state) next(bars(fc), state)
> @deprecate done(fc::FooCollection, state) done(bars(fc), state)
> This works and gives deprecation messages when I write for bar in
> foos() println(bar) end, but the messages aren’t very helpful; for
> one thing, I get three of them (one for each method), and for another
> they refer to functions which aren’t present in the user’s code (and
> which the user won’t realize why they’re called unless they know how
> to implement iterators in Julia…).
>
> Is there a better/more helpful way to do this, without having to re-
> implement the @deprecate machinery entirely?
You can call depwarn() directly from inside these functions, and print
a custom message like "iteration over FooCollection is deprecated". See
base/deprecated.jl for examples.
Regards
