On Thursday, 16 July 2015 at 20:41:21 UTC, ZombineDev wrote:
On Thursday, 16 July 2015 at 20:17:54 UTC, Jarl André Hübenthal
wrote:
On Thursday, 16 July 2015 at 20:00:38 UTC, Ali Çehreli wrote:
On 07/16/2015 12:35 PM, "Jarl
=?UTF-8?B?QW5kcsOpIEjDvGJlbnRoYWwi?= <jarl.an...@gmail.com>"
wrote:
Hi
using mongo with vibe.d is easy. But I would like to skip
the foreach on
MongoCursor?
I mean, I want to use map!, filter! and reduce! on the
resulting docs.
Is there a fast way to convert MongoCursor to an array
without resolving
to ugly for loops with appender! ?
I've never used MongoCursor but judging from the fact that it
has empty, front, and popFront(), it is an InputRange:
http://vibed.org/api/vibe.db.mongo.cursor/MongoCursor
Have you tried using it with map and others? What errors do
you get?
Ali
Ah well I got another error now. Using the following code:
Resource[] getResource() {
auto coll = client.getCollection("app.resource");
return coll.find().map!(doc => deserialize!(BsonSerializer,
Resource)(doc));
}
I get this error:
src/app.d(51,21): Error: cannot implicitly convert expression
(map(coll.find())) of type MapResult!(__lambda1,
MongoCursor!(Bson, Bson, typeof(null))) to Resource[]
Most of the functions from std.algorithm and std.range return a
lazy range which you need to iterate over go get its elements.
To turn those ranges to an array you need add a .array at the
end (http://dlang.org/phobos/std_array#array). Here's a larger
example: http://d.readthedocs.org/en/latest/introduction.html.
Another option is to return the elements as a range (by making
return type of your function auto), instead of putting them
into a newly allocated array (with .array). This way may be a
bit more work (delaying the call to .array), but it can be
quite efficient because it removes the need to allocate memory.
Thanks. Its a lot more cleaner and syntactically readable having
.array at the end. But about laziness the same applies to clojure
and scala. In clojure you must force evaluate the list, in scala
you must to mostly the same as in D, put a toList or something at
the end. Or loop it. But its pretty nice to know that there is
laziness in D, but when I query mongo I expect all docs to be
retrieved, since there are no paging in the underlying queries?
Thus, having a lazy functionality on top of non lazy db queries
seem a bit off dont you think?
