json interface

The json interface is a json object describing the Application Binary Interface (ABI) for a smart contract. Using this json interface, web3.js is able to create JavaScript object representing the smart contract and its methods and events using the web3.eth.Contract object.

Specification

Functions:

  1. type: "function", "constructor" (can be omitted, defaulting to "function"; "fallback" also possible but not relevant in web3.js).

  2. name: the name of the function (only present for function types).

  3. constant: true if function is specified to not modify the blockchain state.

  4. payable: true if function accepts ether, defaults to false

  5. stateMutability: a string with one of the following values:

    1. pure (specified to not read blockchain state)

    2. view (same as constant above)

    3. nonpayable and payable (same as payable above)

  6. inputs: an array of objects, each of which contains:

    1. name: the name of the parameter

    2. type: the canonical type of the parameter

  7. outputs: an array of objects same as inputs, can be omitted if no outputs exist.

Events:

  1. type: always "event"

  2. name: the name of the event.

  3. inputs: an array of objects, each of which contains:

    1. name: the name of the parameter.

    2. type: the canonical type of the parameter.

    3. indexed: true if the field is part of the log's topics, false if it one of the log's data segment.

  4. anonymous: true if the event was declared as anonymous.

Example:

contract Test {
uint a;
address d = 0x12345678901234567890123456789012;
function Test(uint testInt) { a = testInt;}
event Event(uint indexed b, bytes32 c);
event Event2(uint indexed b, bytes32 c);
function foo(uint b, bytes32 c) returns(address) {
Event(b, c);
return d;
}
}
// would result in the JSON:
[{
"type":"constructor",
"payable":false,
"stateMutability":"nonpayable"
"inputs":[{"name":"testInt","type":"uint256"}],
},{
"type":"function",
"name":"foo",
"constant":false,
"payable":false,
"stateMutability":"nonpayable",
"inputs":[{"name":"b","type":"uint256"}, {"name":"c","type":"bytes32"}],
"outputs":[{"name":"","type":"address"}]
},{
"type":"event",
"name":"Event",
"inputs":[{"indexed":true,"name":"b","type":"uint256"}, {"indexed":false,"name":"c","type":"bytes32"}],
"anonymous":false
},{
"type":"event",
"name":"Event2",
"inputs":[{"indexed":true,"name":"b","type":"uint256"},{"indexed":false,"name":"c","type":"bytes32"}],
"anonymous":false
}]