Reference · Records and errors

unwrap

unwrap(any) -> any

What it does

The value itself when it is not an error value, and a runtime error when it is. It turns an error value into a stop: the request fails with a 500 and the error's payload in the message. Use it where an error cannot happen in practice and a silent default would hide a bug; use ?? for a default and ? to pass the error on.

Examples

print(unwrap(int("42")), unwrap("a"), unwrap([1, 2]))let config = unwrap(json.parse(`{"port": 8080}`))print(config.port)

42 a [1, 2]8080

Edge cases

• null is not an error: unwrap(null) is null.
• The payload goes into the message as text: a map payload shows as a map, a null payload as null.
• ?? after unwrap comes too late: the runtime error has already stopped the program. Put ?? on the value instead.

print(unwrap(null), unwrap(false))print(int("x") ?? 0)

null false0

Errors

An error value is a runtime error, not an error value: the message is unwrap of an error: and the payload.

print(unwrap(err("missing")))

line 1: unwrap of an error: missing

print(unwrap(err({ code: 404 })))

line 1: unwrap of an error: { code: 404 }

Chaining

print(["1", "2"] | map(int) | map(unwrap))print(`[1, 2]` | json.parse | unwrap | sum)

[1, 2]3

See also

err, is_err, int, json.parse

Edit this page on GitHub · every example's output was made by running it (tools/refcheck.mjs) · questions on Discord or r/quillo