Ethereum Oraclize tutorial on a private network (Tobalaba test network)

For educational purposes. Supplement to this ewf wiki post. The examples were taken from the oraclize/ethereum-examples repo, then extended/modified to make them more wholesome.

Tested with Parity client version 1.11.6 Beta.

Dependencies

• Connection to Tobalaba. For a tutorial on how to set up a local Parity client and connect to the network, check here.
• Two accounts with some test Ethers in it. You can use the Parity UI for this purpose, then navigate to the faucet to get some ethers.
• Ethereum-bridge
• Truffle

Setup

Ethereum-bridge

After you have the Parity client running, you need to set up a connection between the private network and Oraclize:

git clone https://github.com/oraclize/ethereum-bridge.git
cd ethereum-bridge
npm install

Then:

node bridge -H localhost:8545 -a 1

When the bridge is launched, sometimes you see the following in the console:

Please add this line to your contract constructor:

OAR = OraclizeAddrResolverI(<an address here>);

You have to add this line to the smart contract constructors. Just replace the existing one.

When you stop the bridge, you see something like this:

To load this instance again: ethereum-bridge --instance oracle_instance_20180813T181443.json
Exiting...

Which means you can run the bridge next time with:

node bridge --instance oracle_instance_20180813T181443.json

and have the same OAR address.

How to use

1. Make sure your parity client is running and configured to connect to Tobalaba
2. Launch ethereum-bridge
3. Clone repo, install web3 (the new 1.x version)

git clone https://github.com/ngyam/tutorial-oraclize.git
cd tutorial-oraclize
npm install web3

4. Migrate, or run the tests

Test

truffle test --network tobalaba

Deploy

truffle migrate --network tobalaba

Resources

Energy Web Foundation

Parity client

Blog

Oraclize doc

Truffle