Initializaion

Call functions and supply arguments as soon as a contract is deployed to a network.

The <clinit> of every class submitted as part of the contract (including all the code within static {} blocks) will be run when the contract is first deployed, and never again. This makes static {} the ideal place to run any contract initialization logic.

Example Contract

package aion;

import avm.Blockchain;
import org.aion.avm.tooling.abi.Callable;
import org.aion.avm.tooling.abi.Initializable;
import org.aion.avm.userlib.abi.ABIDecoder;
public class ClinitExample {

    @Initializable
    private static String myString;
  
    @Initializable
    private static int[] intArray;

    static {
        // Log myString upon deployment.
        logMyString("MyStringInitialization");
    }

    //Emit Event
    @Callable
    public static void logMyString(String topic){
        Blockchain.log(topic.getBytes(), Blockchain.getCaller().toByteArray(), myString.getBytes());
    }


    // Return the private String.
    @Callable
    public static String getString() {
        return myString;
    }
  
    @Callable
    public static int getIntFromArray(int index) {
        return intArray[index];
    }
}

Initialize variables

You can initialize contract variables by passing in arguments while you deploy your smart contract. To do that, you can use either @Initializable fields (in the first tab) or an ABIDecoder to collect the data (in the second tab).

Using @Initializable field

Annotating variables with @Initializable will collect the data that was passed into the contract upon deployment.

@Initializable
private static String myString;

@Initializable
private static int[] intArray;

Using ABIDecoder

To capture deployment arguments you can an ABIDecoder object and use Blockchain.getData()) method to get the data that is passed into the contract upon deployment. You must decode those variables in the exact same order as they were passed in.

static {
    ABIDecoder decoder = new ABIDecoder(Blockchain.getData());
    myStr = decoder.decodeOneString();
    myIntArray = decoder.decodeOneIntegerArray();
    myTwoDIntArray = decoder.decodeOne2DIntegerArray();
}

Call Contract Methods

You can also call contract methods within static {} function, method can be both @Callable method and private method. For example:

static {
    logMyString("MyStringInitialization");
}

//Emit Event
@Callable
public static void logMyString(String topic){
    Blockchain.log(topic.getBytes(), Blockchain.getCaller().toByteArray(), myString.getBytes());
}

Here we are calling logMyString(String topic) to log the initial string value of myString under topicMyStringIntialization and the account that deployed the contract.

For example, set myString to Hello AVM upon contract deployment. Deploy the contract and the log in the receipt of this deployment will be:

"logs": [{
    "address": "0xa025257b822b5d18c64bdea28319ca356df7e9db5b31f5d9fbe837876cdd5245",
    "logIndex": "0x0",
    "data": "0x48656c6c6f2041564d",
    "topics": [
      "0x4d79537472696e67496e697469616c697a6174696f6e00000000000000000000",
      "0xa0d6dec327f522f9c8d342921148a6c42f40a3ce45c1f56baa7bfa752200d9e5"
    ]

Where:

1. 0x4d79537472696e67496e697469616c697a6174696f6e00000000000000000000 is the hex data of MyStringInitialization.
2. 0xa0d6dec327f522f9c8d342921148a6c42f40a3ce45c1f56baa7bfa752200d9e5 is the account deployed the contract;
3. 0x48656c6c6f2041564d is the hex data of _Hello AVM.