Preimage¶

Calls¶

note_preimage¶

Register a preimage on-chain.

If the preimage was previously requested, no fees or deposits are taken for providing the preimage. Otherwise, a deposit is taken proportional to the size of the preimage.

Attributes¶

Name	Type
bytes	`Vec<u8>`

Python¶

call = substrate.compose_call(
    'Preimage', 'note_preimage', {'bytes': 'Bytes'}
)

request_preimage¶

Request a preimage be uploaded to the chain without paying any fees or deposits.

If the preimage requests has already been provided on-chain, we unreserve any deposit a user may have paid, and take the control of the preimage out of their hands.

Attributes¶

Name	Type
hash	`T::Hash`

Python¶

call = substrate.compose_call(
    'Preimage', 'request_preimage', {'hash': 'scale_info::16'}
)

unnote_preimage¶

Clear an unrequested preimage from the runtime storage.

If len is provided, then it will be a much cheaper operation.

hash: The hash of the preimage to be removed from the store.
len: The length of the preimage of hash.

Attributes¶

Name	Type
hash	`T::Hash`

Python¶

call = substrate.compose_call(
    'Preimage', 'unnote_preimage', {'hash': 'scale_info::16'}
)

unrequest_preimage¶

Clear a previously made request for a preimage.

NOTE: THIS MUST NOT BE CALLED ON hash MORE TIMES THAN request_preimage.

Attributes¶

Name	Type
hash	`T::Hash`

Python¶

call = substrate.compose_call(
    'Preimage', 'unrequest_preimage', {'hash': 'scale_info::16'}
)

Events¶

Cleared¶

A preimage has ben cleared.

Attributes¶

Name	Type	Composition
hash	`T::Hash`	`scale_info::16`

Noted¶

A preimage has been noted.

Attributes¶

Name	Type	Composition
hash	`T::Hash`	`scale_info::16`

Requested¶

A preimage has been requested.

Attributes¶

Name	Type	Composition
hash	`T::Hash`	`scale_info::16`

Storage functions¶

PreimageFor¶

Python¶

result = substrate.query(
    'Preimage', 'PreimageFor', [('scale_info::16', 'u32')]
)

Return value¶

'Bytes'

StatusFor¶

The request status of a given hash.

Python¶

result = substrate.query(
    'Preimage', 'StatusFor', ['scale_info::16']
)

Return value¶

{
    'Requested': {
        'count': 'u32',
        'deposit': (None, ('AccountId', 'u128')),
        'len': (None, 'u32'),
    },
    'Unrequested': {'deposit': ('AccountId', 'u128'), 'len': 'u32'},
}

Errors¶

AlreadyNoted¶

Preimage has already been noted on-chain.

NotAuthorized¶

The user is not authorized to perform this action.

NotNoted¶

The preimage cannot be removed since it has not yet been noted.

NotRequested¶

The preimage request cannot be removed since no outstanding requests exist.

Requested¶

A preimage may not be removed when there are outstanding requests.

TooBig¶

Preimage is too large to store on-chain.