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Create a Smart Contract

Create a Smart Contract

In this section, you’ll learn how to write and compile a WAX smart contract using eosio-init.

How it Works

eosio-init is a WAX-CDT tool that creates the following smart contract template/directory structure:

  • include folder: This includes a sample .hpp file.
  • ricardian folder: This includes a sample Ricardian contract markdown file.
  • src folder: This includes a sample .cpp smart contract file.

The template files are named after the project name you specify when you use eosio-init from the command line.

Use eosio-init

To create your first WAX smart contract using eosio-init:

  1. Create a smart contracts directory. For this tutorial, we’ll use a folder named mycontracts.

     mkdir mycontracts
     Navigate to this new directory:
     cd mycontracts
  2. From the command line, use eosio-init with the -project parameter.

     eosio-init -project wax

    eosio-init uses the -project name to create the following directory structure:

    • mycontracts/wax/include
    • mycontracts/wax/ricardian
    • mycontracts/wax/src
  3. Optional. Add a Ricardian Clause. A Ricardian Contract is already included by default.

You should now have a smart contract template, including a sample smart contract (mycontracts/wax/src/wax.cpp). This contract includes the following action:

#include <wax.hpp>
ACTION wax::hi( name nm ) {
   /* fill in action body */
   print_f("Name : %\n",nm);

The header file (mycontracts/wax/include/wax.hpp) inherits from <eosio/eosio.hpp>.

// Inherit your contract from eosio::contract. 
// This exposes the following data types (available to your smart contract):
// eosio::name receiver - the contract that receives an action (this contract)
// eosio::name code - the contract's blockchain account
// eosio::datastream - the data that's passed to the contract. In this example, it's  your name.
#include <eosio/eosio.hpp>
using namespace eosio;

CONTRACT wax : public contract {
      using contract::contract;

      // The ACTION keyword implements the behavior of your contract. 
      // ACTION is a shortcut for [[eosio::action]]  
      ACTION hi( name nm );

      //action_wrapper: first parameter = action to call
      //second parameter = pointer to the action function
      using hi_action = action_wrapper<"hi"_n, &wax::hi>;

Tip: The action_wrapper struct creates a template/pointer based off of a specific action. You can use action_wrappers to make action calls from one contract to another.

Compile Your Contract

To deploy your smart contract, you’ll need to create a .wasm and .abi file. You can do this using the WAX Contract Development Toolkit (WAX-CDT).

  1. Install WAX-CDT (if you haven’t done so already).

  2. From the command line, navigate to the mycontracts/wax build folder.

     cd wax/build
  3. Initialize cmake to write the necessary build files to the build directory.

     cmake ..

    The console prints the following build tasks:

     -- The C compiler identification is GNU 7.4.0
     -- The CXX compiler identification is GNU 7.4.0
     -- Check for working C compiler: /usr/bin/cc
     -- Check for working C compiler: /usr/bin/cc -- works
     -- Detecting C compiler ABI info
     -- Detecting C compiler ABI info - done
     -- Build files have been written to: waxblockchain/wax-blockchain/wax-cdt/examples/hello/build
  4. Build the scripts.


    The console prints the following confirmation:

     Scanning dependencies of target wax
     [ 50%] Building CXX object CMakeFiles/wax.dir/wax.obj
     Warning, empty ricardian clause file
     [100%] Linking CXX executable wax.wasm
     [100%] Built target wax
     [ 77%] No install step for 'wax_project'
     [ 88%] No test step for 'wax_project'
     [100%] Completed 'wax_project'
     [100%] Built target wax_project

You can locate the wax.wasm and wax.abi files in the build/wax directory.