Smart Contracts
Lottery Smart Contract

Lottery Smart Contract Guide

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Testnet Tutorial: This guide uses testnet ports (40402/40403). Always test smart contracts on testnet before deploying to mainnet. For mainnet, use ports 10102 (daemon) and 10103 (wallet).

Dero Stargate DVM Smart Contracts guide to install and test various functions of the lottery Smart Contract.

  1. Download Dero Stargate testnet source and binaries.

  2. Start Dero daemon in testnet mode:

    ./derod-linux-amd64 --testnet

  3. Start Dero wallet in testnet:

    dero-wallet-cli-linux-amd64 --rpc-server --wallet-file testnet.wallet --testnet

  4. Start a second Dero wallet instance to test transfer/ownership functions, etc.:

    dero-wallet-cli-linux-amd64 --wallet-file testnet2.wallet --testnet --rpc-server --rpc-bind=127.0.0.1:40403

  5. Dero testnet Explorer:

    ./explorer-linux-amd64 --rpc-server-address 127.0.0.1:30306 --http-address=0.0.0.0:8080

Installing Smart Contract

curl --request POST --data-binary @lottery.bas http://127.0.0.1:40403/install_sc

Download SC Code, Check Balance, and Variables from SC

curl http://127.0.0.1:40402/json_rpc -d '{"jsonrpc":"2.0","id":"0","method":"getsc","params":{"scid":"30b84e9ab5baeee7195e7e1ccb1f533b7402beb2d3cfa97216a6d80c01056f66", "code":true}}' -H 'Content-Type: application/json'
 
curl http://127.0.0.1:40402/json_rpc -d '{"jsonrpc":"2.0","id":"0","method":"getsc","params":{"scid":"30b84e9ab5baeee7195e7e1ccb1f533b7402beb2d3cfa97216a6d80c01056f66", "code":false, "keysstring":["deposit_count"]}}' -H 'Content-Type: application/json'

Examples of Various Lottery Smart Contract Functions

Play Lottery

This function enters the lottery by sending DERO to the contract. The value parameter is set by the deposit amount.

curl http://127.0.0.1:40403/json_rpc -d '{
  "jsonrpc": "2.0",
  "id": "0",
  "method": "scinvoke",
  "params": {
    "sc_dero_deposit": 200000,
    "scid": "30b84e9ab5baeee7195e7e1ccb1f533b7402beb2d3cfa97216a6d80c01056f66",
    "sc_rpc": [
      {"name": "entrypoint", "datatype": "S", "value": "Lottery"}
    ]
  }
}' -H 'Content-Type: application/json'

Note: When deposit_count reaches the value set in lotteryeveryXdeposit (default is 2), the lottery will trigger and randomly select a winner from all participants.

Withdraw Balance (Smart Contract Owner Only)

The contract owner can withdraw accumulated fees from the contract.

curl http://127.0.0.1:40403/json_rpc -d '{
  "jsonrpc": "2.0",
  "id": "0",
  "method": "scinvoke",
  "params": {
    "scid": "30b84e9ab5baeee7195e7e1ccb1f533b7402beb2d3cfa97216a6d80c01056f66",
    "sc_rpc": [
      {"name": "entrypoint", "datatype": "S", "value": "Withdraw"},
      {"name": "amount", "datatype": "U", "value": 100000}
    ]
  }
}' -H 'Content-Type: application/json'

Transfer Ownership (Owner Only)

Initiates the ownership transfer process. The new owner must claim ownership to complete the transfer.

curl http://127.0.0.1:40403/json_rpc -d '{
  "jsonrpc": "2.0",
  "id": "0",
  "method": "scinvoke",
  "params": {
    "scid": "30b84e9ab5baeee7195e7e1ccb1f533b7402beb2d3cfa97216a6d80c01056f66", 
    "sc_rpc": [
      {"name": "entrypoint", "datatype": "S", "value": "TransferOwnership"},
      {"name": "newowner", "datatype": "S", "value": "deto1qy..."}
    ]
  }
}' -H 'Content-Type: application/json'

Claim Ownership (New Owner Only)

The designated new owner must call this function to complete the ownership transfer process.

curl http://127.0.0.1:40403/json_rpc -d '{
  "jsonrpc": "2.0",
  "id": "0",
  "method": "scinvoke",
  "params": {
    "scid": "30b84e9ab5baeee7195e7e1ccb1f533b7402beb2d3cfa97216a6d80c01056f66",
    "sc_rpc": [
      {"name": "entrypoint", "datatype": "S", "value": "ClaimOwnership"}
    ]
  }
}' -H 'Content-Type: application/json'

Update Code (Owner Only)

Allows the owner to update the smart contract code. Use with caution as this changes the contract behavior.

curl http://127.0.0.1:40403/json_rpc -d '{
  "jsonrpc": "2.0",
  "id": "0",
  "method": "scinvoke",
  "params": {
    "scid": "30b84e9ab5baeee7195e7e1ccb1f533b7402beb2d3cfa97216a6d80c01056f66",
    "sc_rpc": [
      {"name": "entrypoint", "datatype": "S", "value": "UpdateCode"},
      {"name": "code", "datatype": "S", "value": "/* Lottery Smart Contract */\nFunction Initialize() Uint64\n..."}
    ]
  }
}' -H 'Content-Type: application/json'

Tune Lottery Parameters (Owner Only)

Adjust how frequently the lottery runs and the percentage of deposits returned to winners.

curl http://127.0.0.1:40403/json_rpc -d '{
  "jsonrpc": "2.0",
  "id": "0",
  "method": "scinvoke",
  "params": {
    "scid": "30b84e9ab5baeee7195e7e1ccb1f533b7402beb2d3cfa97216a6d80c01056f66",
    "sc_rpc": [
      {"name": "entrypoint", "datatype": "S", "value": "TuneLotteryParameters"},
      {"name": "lotteryeveryXdeposit", "datatype": "U", "value": 5},
      {"name": "lotterygiveback", "datatype": "U", "value": 9800}
    ]
  }
}' -H 'Content-Type: application/json'

Note: lotterygiveback is measured in basis points (1/100 of a percent). 9800 means 98% returned to winners, 2% kept as fees.

Lottery.bas

/* Lottery Smart Contract in DVM-BASIC
This lottery smart contract will give lottery wins every xth try. */

Function Lottery(value Uint64) Uint64
    10 dim deposit_count,winner as Uint64
    20 LET deposit_count =  LOAD("deposit_count")+1
    25 IF value == 0 THEN GOTO 110  // if deposit amount is 0, simply return
    30 STORE("depositor_address" + (deposit_count-1), SIGNER()) // store address for later on payment
    40 STORE("deposit_total", LOAD("deposit_total") + value )
    50 STORE("deposit_count", deposit_count)
    60 IF LOAD("lotteryeveryXdeposit") > deposit_count THEN GOTO 110 // wait till X players join in
    70 LET winner  = RANDOM() % deposit_count // we have a winner
    80 SEND_DERO_TO_ADDRESS(LOAD("depositor_address" + winner) , LOAD("lotterygiveback")*LOAD("deposit_total")/10000)

    // Reinitialize for another round
    90 STORE("deposit_count", 0)   // initial players
    100 STORE("deposit_total", 0)  // total deposit of all players
    110 RETURN 0
End Function

// Function used to initialize parameters during install time
Function Initialize() Uint64
    10 STORE("owner", SIGNER())  // store in DB ["owner"] = address
    20 STORE("lotteryeveryXdeposit", 2)  // lottery rewards every X deposits
    30 STORE("lotterygiveback", 9900)  // lottery gives back 99% of deposits, 1% accumulated for owner to withdraw
    33 STORE("deposit_count", 0)  // initial players
    34 STORE("deposit_total", 0)  // total deposit of all players
    // 35 printf "Initialize executed"
    40 RETURN 0 
End Function

// Used to tune lottery parameters
Function TuneLotteryParameters(lotteryeveryXdeposit Uint64, lotterygiveback Uint64) Uint64
    10 dim key, stored_owner as String
    20 dim value_uint64 as Uint64
    30 IF LOAD("owner") == SIGNER() THEN GOTO 100 // check whether owner is real owner
    40 RETURN 1  // non-zero return means error: not owner

    100 STORE("lotteryeveryXdeposit", lotteryeveryXdeposit)  // lottery rewards every X deposits
    130 STORE("lotterygiveback", lotterygiveback)  // lottery gives back in 1/10000 parts, granularity .01%
    140 RETURN 0  // zero return means success
End Function

// Function used to change owner, owner is a string form of address
Function TransferOwnership(newowner String) Uint64 
    10 IF LOAD("owner") == SIGNER() THEN GOTO 30 
    20 RETURN 1
    30 STORE("tmpowner", ADDRESS_RAW(newowner))
    40 RETURN 0
End Function

// Until the new owner claims ownership, the existing owner remains the owner
Function ClaimOwnership() Uint64 
    10 IF LOAD("tmpowner") == SIGNER() THEN GOTO 30 
    20 RETURN 1
    30 STORE("owner", SIGNER()) // ownership claim successful
    40 RETURN 0
End Function

// If signer is the owner, withdraw any requested funds
Function Withdraw(amount Uint64) Uint64 
    10 IF LOAD("owner") == SIGNER() THEN GOTO 30 
    20 RETURN 1
    30 SEND_DERO_TO_ADDRESS(SIGNER(), amount)
    40 RETURN 0
End Function

// If signer is the owner, provide rights to update code anytime
Function UpdateCode(code String) Uint64 
    10 IF LOAD("owner") == SIGNER() THEN GOTO 30 
    20 RETURN 1
    30 UPDATE_SC_CODE(code)
    40 RETURN 0
End Function

Related Pages

Learn Smart Contract Programming:

Other Smart Contract Examples:

Deploy & Test: