getfield with integer index argument

[WestleyArgentum]

When I want to iterate over all the members of a type the first valid syntax that comes to mind is roughly:

members = names(thing)
for name in members
    ...
end

But this might be pretty inefficient (I only looked deep enough to see a call to collect, I'm assuming it's creating a new array each time).

Maybe this has been discussed before, but wouldn't it be nice if I could:

for (name, value) in thing  # <--- treat the type like a dictionary
    ...
end

and count on things in the background to not allocate an array?

[quinnj]

Not sure if this is quite what you had in mind, but it seems pretty trivial to implement for your own type. Or are you asking this be a general feature of types in Base?

In  [1]: type Foo
    a
    b
    c
    d
end

In  [2]: importall Base
start(x::Foo) = 1
done(x::Foo, i) = length(names(Foo)) == i-1
next(x::Foo, i) = ((string(names(Foo)[i]),getfield(x,names(Foo)[i])), i+1)
bar = Foo(1,2,3,4)

Out [2]: Foo(1,2,3,4)

In  [3]: for x in bar
    println(x)
end
("a",1)
("b",2)
("c",3)
("d",4)

[JeffBezanson]

I'm planning to add getfield(x, i) where i is an integer field index. This will allow efficient sequential access to all object fields. It could be wrapped with a custom iterator called something like struct2dict.

[WestleyArgentum]

That's exactly what I want, thanks for the update!
On Nov 13, 2013 9:34 PM, "Jeff Bezanson" notifications@github.com wrote:

I'm planning to add getfield(x, i) where i is an integer field index.
This will allow efficient sequential access to all object fields. It could
be wrapped with a custom iterator called something like struct2dict.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/4806#issuecomment-28460832
.

[WestleyArgentum]

Woo!
On Jan 12, 2014 8:46 PM, "Jeff Bezanson" notifications@github.com wrote:

Closed #4806 #4806 via bff951ehttps://github.com/JuliaLang/julia/commit/bff951e1724c706eb74f82faae7f5025c78eb8b8
.

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Reply to this email directly or view it on GitHubhttps://github.com//issues/4806
.

[mathpup]

Has this been added to the documentation? This sounds like a pretty significant and useful addition.

[StefanKarpinski]

Not yet. I think this is still in "banging on the tires" mode, but it should be soon.