The third episode of my Clojure Tip of the Day screencast is out.
You can find the video on YouTube: Clojure Tip of the Day - Episode 3: Threading macros tracing
The episode shows a quick "debugging" technique using the
println function to print intermediate values flowing through the threading macros to the standard output.
For thread-first macro you can use
(doto println) to quickly print intermediate value
Usually, it’s better and more convenient to introduce little helper function *spy* :
(def spy #(do (println "DEBUG:" %) %)) which then works for all threading macros
If you want to use doto-like method then you need to wrap in an anonymous function:
(#(doto % println)) (notice extract parentheses - see macro-expansion of threading macros)