Hook

[Source]

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

A Hook object describes a smart contract, which can be triggered by a transaction to perform predefined operations. The operations are defined by the Hook creator and can interact with the ledger and transactions.

Example JSON

{
  "Account": "rUn84CUYbNjRoTQ6mSW7BVJPSVJNLb1QLo",
  "OwnerNode": "0000000000000000",
  "PreviousTxnID": "5463C6E08862A1FAE5EDAC12D70ADB16546A1F674930521295BC082494B62924",
  "PreviousTxnLgrSeq": 6,
  "Hooks": [
    {
      "HookHash": "46060241FABCF692D4D934BA2A6C4427CD4279083E38C77CBE642243E43BE291",
      "HookParameters": []
    }
  ],
  "LedgerEntryType": "Hook",
  "index": "49647F0D748DC3FE26BDACBC57F251AADEFFF391403EC9BF87C97F67E9977FB0"
}

Fields

A Hook object has the following fields:

Field	JSON Type	[Internal Type][]	Required?	Description
Account	String	Account	Yes	The account that created the Hook.
OwnerNode	String	UInt64	Yes	A hint indicating which page of the owner’s directory links to this object, in case the directory consists of multiple pages.
PreviousTxnID	String	Hash256	Yes	The ID of the transaction that most recently modified this object.
PreviousTxnLgrSeq	Number	UInt32	Yes	The [ledger index][] of the ledger that contains the transaction that most recently modified this object.
Hooks	Array	Array	Yes	An array of hook objects. Each object has the following fields: HookHash, CreateCode, HookGrants, HookNamespace, HookParameters, HookOn, HookApiVersion, Flags.
LedgerEntryType	String	UInt16	Yes	The value 0x0043, mapped to the string Hook, indicates that this object is a Hook object.

Hook Fields

The following fields are used in the hook object:

Field	JSON Type	Internal Type	Description
HookHash	String	Hash256	The hash of the hook.
HookParameters	Array	Array	The parameters of the hook.
Flags	Number	UInt32	Additional flags for the hook.

Hook ID Format

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

• The Hook space key (0x0048)
• The AccountID of the sender of the [SetHook transaction][] that created the Hook object