Access data from a Lazy Sequence

Question

I am trying to retrieve data from a DB. The data is coming back in a lazy sequence. I can peek at the data in repl and it looks like this:

({:foo value1, :bar value2})

How can I get at this data? preferably, how can I turn it into a map? I've tried:

(doall sequence (get sequence :foo)) Which just returns nil. And

(apply hash-map user-settings)

which returns

llegalArgumentException No value supplied for key: {:foo value1, :bar value2} clojure.lang.PersistentHashMap.create (PersistentHashMap.java:77)

I am very new to clojure and have been stuck on this for way too long. Thanks in advance.

The data is coming back in a lazy sequence - A lazy sequence of what? You have a sequence of one record represented by map {:foo value1, :bar value2}. Can you have several such records? How do you want to combine them into a map/table? Is there a key within the record you want to index them by? — Thumbnail
– Thumbnail, Commented Dec 16, 2016 at 19:03

Josh · Accepted Answer · 2016-12-16 18:53:48Z

3

You already have a map, it just happens to be the only item in your list.

(def data (first '({:foo 123 :bar 456})))

(:foo data)  ; => 123

answered Dec 16, 2016 at 18:53

Josh

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KettuJKL · Accepted Answer · 2016-12-22 19:09:03Z

2

Sometimes when you want to print lazy seq to see your data use into. For example if you want to see contents of a lazy vector use (into [] your-lazy-vector) or (into {} your-lazy-map).

You can do this uncool conversion within a println function or in a let. However, I recommend removing this kind of debugging aid before release or pull-request.

Lazy sequences are great, most of the time.

answered Dec 22, 2016 at 19:09

KettuJKL

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