Formatting & Display

An ISIN has a single canonical rendering, the 12-character string. Rendering never allocates on the heap.

Canonical form

Isin::as_str() returns the 12-character string, e.g. "US0378331005". Internally this is a zero-cost borrow of the identifier’s own byte buffer. It never allocates and never panics, because the bytes are guaranteed to be valid ASCII by construction.

use ftracker_identifiers::Isin;

let isin = Isin::parse("us0378331005").unwrap();
assert_eq!(isin.as_str(), "US0378331005"); // normalized to uppercase

If you need raw bytes instead of a &str, Isin::as_bytes() returns &[u8; 12] directly.

Display and Debug

Isin implements Display by writing its canonical string, so isin.to_string() and {} formatting both produce the 12-character form:

use ftracker_identifiers::Isin;

let isin = Isin::parse("US0378331005").unwrap();
assert_eq!(isin.to_string(), "US0378331005");

Debug wraps the same string in a readable tuple-struct style, which is what you’ll see in assert_eq! failure messages, logs, and {:?} output:

Isin("US0378331005")

This makes a mismatched or unexpected Isin easy to spot at a glance in test output or logs, without needing to manually reformat raw bytes.