Function hdk::entry::must_get_header [−][src]
pub fn must_get_header(
header_hash: HeaderHash
) -> ExternResult<SignedHeaderHashed>
Expand description
MUST get a SignedHeaderHashed at a given HeaderHash.
The SignedHeaderHashed is NOT guaranteed to be a valid (or even validated) Element.
For example, an invalid Header could be published and must_get_header
would return the SignedHeaderHashed
.
This may be useful during validation callbacks where the validity depends on a Header existing regardless of its associated Entry. For example, we may simply need to check that the author is the same for two referenced Headers.
must_get_header
is available in contexts such as validation where both determinism and network access is desirable.
A SignedHeaderHashed
will NOT be returned if:
- @TODO The header is WITHDRAWN by the author
- @TODO The header is ABANDONED by ALL authorities
- Nobody knows about it on the currently visible network
If a SignedHeaderHashed
fails to be returned:
- Callbacks will return early with
UnresolvedDependencies
- Zome calls will receive a
WasmError
from the host