Local Deployment with Neo-Express

Back to Deploying Contracts

Neo-Express provides a local Neo N3 blockchain for development. It supports single-node chains, account management, contract deployment, and method invocation.

Prerequisites

• Neo-Express installed (see Installation)
• jq for JSON inspection
• A compiled contract (.nef + .manifest.json)

Step 1: Create a Local Chain

NEOXP=./build/dotnet-tools/neoxp

# Create a fresh single-node chain
$NEOXP create -f -o chain.neo-express

The -f flag forces overwrite if a chain file already exists.

Step 2: Fund the Deployer Account

Neo-Express creates a genesis account with all NEO and GAS. Transfer GAS to the deployer:

$NEOXP transfer -i chain.neo-express 100 GAS genesis node1

This gives node1 enough GAS to cover deployment and invocation costs.

Step 3: Deploy the Contract

$NEOXP contract deploy -i chain.neo-express build/MyContract.nef node1

The output includes:

• contract-hash -- the deployed contract's script hash
• tx-hash -- the deployment transaction hash

To capture the contract hash programmatically:

DEPLOY_OUT="$($NEOXP contract deploy -i chain.neo-express build/MyContract.nef node1 -j)"
CONTRACT_HASH="$(echo "$DEPLOY_OUT" | jq -r '.["contract-hash"]')"
echo "Deployed at: $CONTRACT_HASH"

Step 4: Invoke Methods

Create a .neo-invoke.json file for each invocation:

{
    "contract": "0x<contract-hash>",
    "operation": "methodName",
    "args": [42, "hello"]
}

Write invocation (creates a transaction, costs GAS):

$NEOXP contract invoke -i chain.neo-express invoke.neo-invoke.json node1

Read-only invocation (no transaction, no GAS cost):

$NEOXP contract invoke -r -j -i chain.neo-express invoke.neo-invoke.json node1

The -r flag runs the invocation as a test (read-only). The -j flag outputs JSON for programmatic parsing.

Step 5: Verify Transaction Results

After a write invocation, inspect the transaction's application log:

TX_HASH="0x<transaction-hash>"
$NEOXP show transaction -i chain.neo-express "$TX_HASH"

Check the VM state and notifications:

APP_LOG="$($NEOXP show transaction -i chain.neo-express "$TX_HASH")"

# VM state should be "HALT" (success)
echo "$APP_LOG" | jq '.["application-log"].executions[0].vmstate'

# Check emitted events
echo "$APP_LOG" | jq '.["application-log"].executions[0].notifications'