Documentation
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Overview ¶
Package dynamic provides Any, a type-erased value that remembers enough to safely recover its concrete type later — Haskell's Data.Dynamic, or the same shape as protobuf's google.protobuf.Any (a type name plus a payload, resolved through a registry), adapted for JSON.
Unlike Rust's std::any::Any (backed by a language-level TypeId, no registration needed) or Go's own reflect.Type (not stable across process restarts or a JSON round-trip), Any needs every concrete type it will ever hold to be Registered under a caller-chosen name first — JSON has no native concept of a stable, portable type identity.
Index ¶
Constants ¶
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Variables ¶
This section is empty.
Functions ¶
func As ¶ added in v0.13.0
As extracts the boxed value as T, returning None if the assertion fails or d holds no value — the Option-native alternative to a raw type assertion on Value().
func Register ¶
Register makes T recoverable from an Any under name — call once, typically from an init(), before any New or UnmarshalJSON call: the registry has no locking, the same assumption gob.Register and protobuf's registry make. name is entirely the caller's choice, never derived from T itself, the same way a protobuf message's type URL comes from its .proto package+name rather than its generated Go type. Register panics on a duplicate name, so a collision fails at init time rather than resolving to the wrong type at some later Unmarshal.
Types ¶
type Any ¶
type Any struct {
// contains filtered or unexported fields
}
Any holds a value of Registered type, type-erased. Use New to construct; never use the zero value directly (though the zero value does happen to hold no value, the same way None[T]() does for Option).
func New ¶
New boxes v, identified by its own runtime type. Panics if that type was never Registered — the same fail-fast stance Register itself takes, and the same shape as option.Some panicking on a nil value: a programmer error, not a condition to recover from.
func (Any) MarshalJSON ¶
MarshalJSON writes null for a zero-value Any (no value ever boxed), or {"@type":...,"value":...} otherwise.
func (*Any) UnmarshalJSON ¶
UnmarshalJSON reads null as a zero-value Any, and {"@type":...,"value":...} as a boxed value of the type "@type" names — an exact lookup, erroring (not panicking — this is untrusted input, unlike New) if that name was never Registered.
Source Files