Hook Definition

[Source]

(Added by the [Hooks amendment][].)

A HookDefinition object describes a hook, which is a piece of code that is executed in response to certain transactions. The hook can modify the transaction, emit new transactions, or perform other actions.

Example JSON

{
  "HookHash": "49647F0D748DC3FE26BDACBC57F251AADEFFF391403EC9BF87C97F67E9977FB0",
  "HookOn": "0000000000000000000000000000000000000000000000000000000000000000",
  "HookNamespace": "0000000000000000000000000000000000000000000000000000000000000000",
  "HookParameters": {
    "HookParameter": {
      "HookParameterName": "DEADBEEF",
      "HookParameterValue": "DEADBEEF",
    }
  },
  "HookApiVersion": 1,
  "CreateCode": "5463C6E08862A1FAE5EDAC12D70ADB16546A1F674930521295BC082494B62924",
  "HookSetTxnID": "0000000000000000",
  "ReferenceCount": "6",
  "Fee": "100000000",
  "HookCallbackFee": "200000000",
  "LedgerEntryType": "HookDefinition",
  "index": "49647F0D748DC3FE26BDACBC57F251AADEFFF391403EC9BF87C97F67E9977FB0"
}

Fields

A HookDefinition object has the following fields:

Field	JSON Type	[Internal Type][]	Required?	Description
HookHash	String	Hash256	Yes	The unique identifier of the hook.
HookOn	String	Hash256	Yes	The transaction/s on which the hook is triggered.
HookCanEmit	String	Hash256	No	The transaction/s which the hook can emit.
HookNamespace	String	Hash256	Yes	The namespace of the hook.
HookParameters	String	Vector	Yes	The parameters that the hook accepts.
HookApiVersion	Number	UInt16	Yes	The version of the hook API that the hook uses.
CreateCode	String	VL	Yes	The code that is executed when the hook is created.
HookSetTxnID	String	Hash256	Yes	The ID of the transaction that set the hook.
ReferenceCount	String	UInt64	Yes	The number of references to the hook.
Fee	String	Amount	Yes	The fee for executing the hook.
HookCallbackFee	String	Amount	No	The fee for executing the hook’s callback function.
LedgerEntryType	String	UInt16	Yes	The value 0x0043, mapped to the string HookDefinition, indicates that this object is a HookDefinition object.

Hook Definition ID Format

The ID of a HookDefinition object is the [SHA-512Half][] of the following values, concatenated in order:

• The HookDefinition space key (0x0044)
• The HookHash of the hook