Serialization converts nested data structures or objects into a linear representation that can be written to disk or sent over a network, then reconstructed. In Clojure, pr-family functions produce representations that read-string can read back, while print-family functions target human-readable output. section 18.2
Choose the representation and output path according to the task:
- Use pr-str or prn-str when a string representation should remain readable by Clojure; use print-str or println-str for human-oriented text. section 18.2
- Bind *out* to a Writer or OutputStream to redirect output, including large lazy sequences, directly to a file. section 18.2
- Extend print-method for readable custom types, and use print-dup with print-ctor when reconstructible forms are required. section 18.4
- Treat print-dup and read-string as unsafe for uncontrolled data because evaluated representations permit code injection; prefer EDN when appropriate. section 18.4
Readable and reconstructible custom data
A Point type can print as "[x=1, y=2]" for ordinary display, while print-dup can emit "#=(user.Point. 1 2)". Reading and evaluating the latter reconstructs a Point instance, but only trusted serialized data should be evaluated. section 18.4
(pr "a" 'a \a) ; #1 ;; "a" a \a ;; nil (print "a" 'a \a) ; #2 ;; a a a ;; nil
Compare pr's reader-friendly quoting with print's human-oriented output for the same values. section 18.2
