Database Reference
In-Depth Information
How it works…
The
let
bindings in
load-data
tell the story here. Let's talk about them one by one.
The irst binding has Enlive download the resource and parse it into Enlive's internal
representation:
(let [page (html/html-resource (URL. url))
The next binding selects the table with the
data
ID:
table (html/select page [:table#data])
Now, select of all the header cells from the table, extract the text from them, convert each to a
keyword, and then convert the entire sequence into a vector. This gives headers for the dataset:
headers (->>
(html/select table [:tr :th])
(map html/text)
(map to-keyword)
vec)
First, select each row individually. The next two steps are wrapped in
map
so that the cells in
each row stay grouped together. In these steps, select the data cells in each row and extract
the text from each. Last, use
filterseq
, which removes any rows with no data, such as the
header row:
rows (->> (html/select table [:tr])
(map #(html/select % [:td]))
(map #(map html/text %))
(filterseq))]
Here's another view of this data. In this image, you can see some of the code from this web
page. The variable names and select expressions are placed beside the HTML structures that
they match. Hopefully, this makes it more clear how the select expressions correspond to the
HTML elements:
