I have compojure based app where I need to parse a request and retrieve parameters that can be numbers. I want to be able to verify that the parameters exist and that they are numbers before actually processing the request. This is what I have so far:
(defn get-int [str]
"Returns nil if str is not a number"
(try (Integer/parseInt str)
(catch NumberFormatException _)))
(defn some-request [request]
(let [some-number (get-int (get-in request [:route-params :some-number])
other-number (get-int (get-in request [:route-params :other-number])]
(if (every? identity [some-number other-number])
(process-the-request)
(bad-request "The request was malformed")))
Is there a better way to do string -> number conversion?
Is there a better way to do request validation?
This question contains good examples for parsing numbers in Clojure. If you are not sure that the string contains a valid number, your approach looks good.
If you can pass the parameters as part of the query string, you could use a route with regex to retrieve the value, e.g.
(GET ["/user/:id", :id #"[0-9]+"] [id]
(let [num (read-string id)]
(str "The number is: " num)))
The route would only match if the regex conditions are met, therefore you could skip the Integer/parseInt check.