Call Workflow
This diagram shows the call execution flow: starting with request_preimage, passing through validation
(signature, nonce, mortality, fee payment), then pre-dispatch checks, followed by dispatch which emits events: Requested and modifies storage: StatusFor, RequestStatusFor, and finally post-dispatch where ExtrinsicSuccess is emitted and fees are settled.
Press enter or space to select a node. You can then use the arrow keys to move the node around. Press delete to remove it and escape to cancel.
Press enter or space to select an edge. You can then press delete to remove it or escape to cancel.
Click items to navigate. Pan and zoom to explore.
Used by: validatorsdevelopers
The Big Picture
Signals governance mechanism needs this.
Use Cases
- Mark preimage as in-use
From Chain Metadata
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.
Input Parameters
| # | Name | Type | Description |
|---|---|---|---|
| 0 | hash | H256 | hash (H256) |
Permissions
Origin
Unknown
Required Role
Permission data inferred from metadata. May be incomplete.
Requirements
- Hash provided
Effects
Events Emitted
Storage Modified
Postconditions
- Preimage marked as requested
Side Effects
- Emits Requested
Code Examples
import { ApiPromise, WsProvider } from "@polkadot/api";
import { stringCamelCase } from "@polkadot/util";
const provider = new WsProvider("wss://entrypoint-finney.opentensor.ai:443");
const api = await ApiPromise.create({ provider });
// Build request_preimage call
const hash = 0 as any /* H256 */;
const call = api.tx[stringCamelCase("Preimage")][stringCamelCase("request_preimage")](
hash
);Runtime Info
- Pallet Index
- 14
- Call Index
- 2
- First Version
- v133
- Current Version
- v393