Bluzelle-Ethereum integration for Apr. 28th hackathon, provided as a Solidity file that implements a wrapper around Oraclize.

To use Bluzelle in a solidity contract, first import bluzelle.sol. If you are using remix, you can do this with just

import "https://github.com/bluzelle/eth-oracle/bluzelle.sol";

If you are using an environment which doesn't handle that for you, you may have to download bluzelle.sol directly as well as its dependancies:

https://github.com/oraclize/ethereum-api/blob/master/oraclizeAPI_0.4.sol https://github.com/Arachnid/solidity-stringutils/blob/master/src/strings.sol

To use the Bluzelle interface, first have your contract extend BluzelleClient

contract MyContract is BluzelleClient {
  ...
}

Call setUUID(string uuid) before making any DB calls - this configures which distinct database you connect to. Your UUID may actually be any string, but you should choose it to be something distinct from anyone else's - such as your contract's address, a random string, or actually a uuid.

Then, DB operations are performed with the following methods:

create("a key", "with some data");
read("a key");
update("a key", "with a new value");
remove("a key");

Each DB operation will consume a small amount of ether to pay Oraclize's fee.

All database operations are performed asynchronously (this is a fundamental constraint of running in Ethereum). If you want to act on the result of your database operations (and presumably you do, at least for reads), then override some or all of the following callback methods

// When a read succeeds
function readResult(string key, string result) internal { ... }

// When a read fails
function readFailure(string key) internal {...}

// When a create, update, remove is performed
function createResponse(string key, bool success) internal {...}
function updateResponse(string key, bool success) internal {...}
function removeResponse(string key, bool success) internal {...}

The included file sample.sol shows an example smart contract that excercises this functionality.

This should work on any network Oraclize supports: Ropsten, Kovan, and Rinkeby as well as the main net. We do not recommend it for use on the main net; it's not known to be reliable or secure enough.

Each database transaction requires a small fee for Oraclize ($0.01 usd worth), and the transaction will fail if the contract balance is too low.

If you neglect to set a UUID before making a DB call, you will end up using the emptry string as your UUID. This may result in Bad Things.