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ContractListener

Table of contents

  1. ContractListener
    1. Example
    2. Field Descriptions
  2. FFIReference
  3. FFISerializedEvent
  4. FFIParam
  5. ContractListenerOptions

ContractListener

A contract listener configures FireFly to stream events from the blockchain, from a specific location on the blockchain, according to a given definition of the interface for that event.

Check out the Custom Contracts Tutorial for a walk-through of how to set up listeners for the events from your smart contracts.

Example 

{
    "id": "d61980a9-748c-4c72-baf5-8b485b514d59",
    "interface": {
        "id": "ff1da3c1-f9e7-40c2-8d93-abb8855e8a1d"
    },
    "namespace": "ns1",
    "name": "contract1_events",
    "backendId": "sb-dd8795fc-a004-4554-669d-c0cf1ee2c279",
    "location": {
        "address": "0x596003a91a97757ef1916c8d6c0d42592630d2cf"
    },
    "created": "2022-05-16T01:23:15Z",
    "event": {
        "name": "Changed",
        "description": "",
        "params": [
            {
                "name": "x",
                "schema": {
                    "type": "integer",
                    "details": {
                        "type": "uint256",
                        "internalType": "uint256"
                    }
                }
            }
        ]
    },
    "signature": "Changed(uint256)",
    "topic": "app1_topic",
    "options": {
        "firstEvent": "newest"
    }
}

Field Descriptions

Field Name Description Type
id The UUID of the smart contract listener UUID
interface A reference to an existing FFI, containing pre-registered type information for the event FFIReference
namespace The namespace of the listener, which defines the namespace of all blockchain events detected by this listener string
name A descriptive name for the listener string
backendId An ID assigned by the blockchain connector to this listener string
location A blockchain specific contract identifier. For example an Ethereum contract address, or a Fabric chaincode name and channel JSONAny
created The creation time of the listener FFTime
event The definition of the event, either provided in-line when creating the listener, or extracted from the referenced FFI FFISerializedEvent
signature The stringified signature of the event, as computed by the blockchain plugin string
topic A topic to set on the FireFly event that is emitted each time a blockchain event is detected from the blockchain. Setting this topic on a number of listeners allows applications to easily subscribe to all events they need string
options Options that control how the listener subscribes to events from the underlying blockchain ContractListenerOptions

FFIReference

Field Name Description Type
id The UUID of the FireFly interface UUID
name The name of the FireFly interface string
version The version of the FireFly interface string

FFISerializedEvent

Field Name Description Type
name The name of the event string
description A description of the smart contract event string
params An array of event parameter/argument definitions FFIParam[]
details Additional blockchain specific fields about this event from the original smart contract. Used by the blockchain plugin and for documentation generation. JSONObject

FFIParam

Field Name Description Type
name The name of the parameter. Note that parameters must be ordered correctly on the FFI, according to the order in the blockchain smart contract string
schema FireFly uses an extended subset of JSON Schema to describe parameters, similar to OpenAPI/Swagger. Converters are available for native blockchain interface definitions / type systems - such as an Ethereum ABI. See the documentation for more detail JSONAny

ContractListenerOptions

Field Name Description Type
firstEvent A blockchain specific string, such as a block number, to start listening from. The special strings ‘oldest’ and ‘newest’ are supported by all blockchain connectors. Default is ‘newest’ string