Curriculum Errors & packaging Type assertions & type switches exercise 3 · mcq
Type assertions & type switches
Pick the IDIOMATIC Go declaration of a CUSTOM ERROR TYPE —
the pattern callers will type-assert / type-switch on with
comma-ok or errors.As.
Custom error types are how you carry STRUCTURED context with
an error (status codes, field paths, retry hints). The
pattern: a struct with relevant fields + a pointer-receiver
Error() string method.
TypeScript reference
About this theme
v.(T) asserts that an interface value v is actually of type T. Panics if wrong. Use the comma-ok form to check first: if t, ok := v.(T); ok { ... }. For multi-branch checks, switch v := i.(type) dispatches on dynamic type.