Hello World

This is the most basic lua smart contract to store and retrieve states in aergo. You can save a name on the blockchain with the contract call function. And you can print ‘hello …’ with the query function.

-- Define global state variables
state.var {
  Name = state.value(),
  My_map = state.map()
}

-- Initialize the state variables
function constructor()
  -- a constructor is called only once at the contract deployment
  Name:set("world")
  My_map["key"] = "value"
end

-- Update the name
-- @call
-- @param name          string: new name
function set_name(name)
  Name:set(name)
end

-- Say hello
-- @query
-- @return              string: 'hello ' + name
function hello()
  return "hello " .. Name:get()
end

-- register functions to expose
abi.register(set_name, hello)

Tutorial

This is explained based on using cli. Variables used in this example are

• Account to deploy and execute a contract: AmPbWrQbtQrCaJqLWdMtfk2KiN83m2HFpBbQQSTxqqchVv58o82i
• cli commands in this page need a aergosvr with enable personal feature

Check Account and Balance

First, you need an account with enough balance to deploy and execute smart contracts. (If you don’t) Import or Unlock Account to aergo server.

Compile Contract

Copy above code and save it to a file (e.g. helloword.lua). And Compile using the aergoluac compiler

./aergoluac --payload helloworld.lua
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

Deploy Contract

With the payload generated above, Deploy contract

./aergocli contract deploy AmPbWrQbtQrCaJqLWdMtfk2KiN83m2HFpBbQQSTxqqchVv58o82i --payload 37mGLDoCPNDQw7HbCG5WPfcM3E3cLhqhgE2V2UJK
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
1 : FPqA3kNQHoVXqKJv8JNpUSsh8F8id87yvRr5UzQFoCcH TX_OK

Get receipt of contract

Look up the actual contract address with the transaction ID above.

./aergocli receipt get FPqA3kNQHoVXqKJv8JNpUSsh8F8id87yvRr5UzQFoCcH
{
 "BlokNo": 317,
 "BlockHash": "48zceVwBZt5dpzuEFMtJB9icPXUu7YG1Xkxvw5N92yFW",
 "contractAddress": "AmfzX3SHXVTBU9NSEWXaLxxjN11KsUpm1Gb3YjF7kmsHrgmL41WU",
 "status": "CREATED",
 "ret": {},
 "txHash": "AWeaoCTpohuQpBMTFaW3qFpZqWwuTehXA8ZkAX59UjMV",
 "txIndex": 0,
 "from": "AmPbWrQbtQrCaJqLWdMtfk2KiN83m2HFpBbQQSTxqqchVv58o82i",
 "to": "",
 "usedFee": 10,
 "events": []
}

If the status is not ‘CREATED’, it may not be included in the block yet, or there may be an error. Wait a while until the transaction is included in the block. Or check the server’s error log.

Get ABI of contract

Look up ABI of contract with the contract address above.

./aergocli contract abi AmfzX3SHXVTBU9NSEWXaLxxjN11KsUpm1Gb3YjF7kmsHrgmL41WU
{
 "version": "0.2",
 "language": "lua",
 "functions": [
  {
   "name": "hello"
  },
  {
   "name": "set_name",
   "arguments": [
    {
     "name": "name"
    }
   ]
  },
  {
   "name": "constructor"
  }
 ],
 "state_variables": [
  {
   "name": "Name",
   "type": "value"
  },
  {
   "name": "My_map",
   "type": "map"
  }
 ]
}

Query Initial State

You can query the generated contract in the following way.

./aergocli contract query AmfzX3SHXVTBU9NSEWXaLxxjN11KsUpm1Gb3YjF7kmsHrgmL41WU hello
value:"\"hello world\""

You can see that the name ‘world’ assigned by the constructor is output.

Call Contract

You can change the name recorded in the block chain as follows:

./aergocli contract call AmPbWrQbtQrCaJqLWdMtfk2KiN83m2HFpBbQQSTxqqchVv58o82i AmfzX3SHXVTBU9NSEWXaLxxjN11KsUpm1Gb3YjF7kmsHrgmL41WU
 set_name '["aergo"]'
1 : 8mcuEFNxNCF6h4Q3FJk3mGN356R1AmWgGptAgJHNfaKs TX_OK

Query Changed State

If you look at the results again, it has changed.

./aergocli contract query AmfzX3SHXVTBU9NSEWXaLxxjN11KsUpm1Gb3YjF7kmsHrgmL41WU hello
value:"\"hello aergo\""

Query contract variable with merkle proof

Value

./aergocli contract statequery AmfzX3SHXVTBU9NSEWXaLxxjN11KsUpm1Gb3YjF7kmsHrgmL41WU Name --compressed

Map

./aergocli contract statequery AmfzX3SHXVTBU9NSEWXaLxxjN11KsUpm1Gb3YjF7kmsHrgmL41WU My_map key --compressed

Array

./aergocli contract statequery AmfzX3SHXVTBU9NSEWXaLxxjN11KsUpm1Gb3YjF7kmsHrgmL41WU array_name array_index --compressed

By default, the returned state is the one at the latest block, but you may specify any past block’s state root.

./aergocli contract statequery AmhbdCEg4TUFm6Hpdoz8d81eSdzRncsekBLN3mYgLCbAVdPnu1MZ var_name --root "9NBSjkcNTdE5ciBxfb52RmsVW7vgX5voRsv6KcosiNjE"