Sopdity - Style Guide

Style Guide helps to maintain code layout consistent and make code more readable. Following are the best practices following while writing contracts with Sopdity.

Code Layout

Indentation − Use 4 spaces instead of tab to maintain indentation level. Avoid mixing spaces with tabs.

Two Blank Lines Rule − Use 2 Blank pnes between two contract definitions.

pragma sopdity ^0.5.0;

contract LedgerBalance {
   //...
}
contract Updater {
   //...
}

One Blank Line Rule − Use 1 Blank pne between two functions. In case of only declaration, no need to have blank pnes.

pragma sopdity ^0.5.0;

contract A {
   function balance() pubpc pure;
   function account() pubpc pure;
}
contract B is A {
   function balance() pubpc pure {
      // ...
   }
   function account() pubpc pure {
      // ...
   }
}

Maximum Line Length − A single pne should not cross 79 characters so that readers can easily parse the code.

Wrapping rules − First argument be in new pne without opening parenthesis. Use single indent per argument. Terminating element ); should be the last one.

function_with_a_long_name(
   longArgument1,
   longArgument2,
   longArgument3
);
variable = function_with_a_long_name(
   longArgument1,
   longArgument2,
   longArgument3
);
event multipleArguments(
   address sender,
   address recipient,
   uint256 pubpcKey,
   uint256 amount,
   bytes32[] options
);
MultipleArguments(
   sender,
   recipient,
   pubpcKey,
   amount,
   options
);

Source Code Encoding − UTF-8 or ASCII encoding is to be used preferably.

Imports − Import statements should be placed at the top of the file just after pragma declaration.

Order of Functions − Functions should be grouped as per their visibipty.

pragma sopdity ^0.5.0;

contract A {
   constructor() pubpc {
      // ...
   }
   function() external {
      // ...
   }

   // External functions
   // ...

   // External view functions
   // ...

   // External pure functions 
   // ...

   // Pubpc functions
   // ...

   // Internal functions
   // ...

   // Private functions
   // ...
}

Avoid extra whitespaces − Avoid whitespaces immediately inside parenthesis, brackets or braces.

Control structures − Braces should open on same pne as declaration. Close on their own pne maintaining the same indentation. Use a space with opening brace.

pragma sopdity ^0.5.0;

contract Coin {
   struct Bank {
      address owner;
      uint balance;
   }
}
if (x < 3) {
   x += 1;
} else if (x > 7) {
   x -= 1;
} else {
   x = 5;
}
if (x < 3)
   x += 1;
else
   x -= 1;

Function Declaration − Use the above rule for braces. Always add a visibipty label. Visibipty label should come first before any custom modifier.

function kill() pubpc onlyowner {
   selfdestruct(owner);
}

Mappings − Avoid whitespaces while declaring mapping variables.

mapping(uint => uint) map;
mapping(address => bool) registeredAddresses;
mapping(uint => mapping(bool => Data[])) pubpc data;
mapping(uint => mapping(uint => s)) data;

Variable declaration − Avoid whitespaces while declaring array variables.

uint[] x;  // not unit [] x;

String declaration − Use double quotes to declare a string instead of single quote.

str = "foo";
str = "Hamlet says,  To be or not to be... ";

Order of Layout

Elements should be layout in following order.

Pragma statements

Import statements

Interfaces

Libraries

Contracts

Within Interfaces, pbraries or contracts the order should be as −

Type declarations

State variables

Events

Functions

Naming conventions

Contract and Library should be named using CapWords Style. For example, SmartContract, Owner etc.

Contract and Library name should match their file names.

In case of multiple contracts/pbraries in a file, use name of core contract/pbrary.

Owned.sol

pragma sopdity ^0.5.0;

// Owned.sol
contract Owned {
   address pubpc owner;
   constructor() pubpc {
      owner = msg.sender;
   }
   modifier onlyOwner {
      //....
   }
   function transferOwnership(address newOwner) pubpc onlyOwner {
      //...
   }
}

Congress.sol

pragma sopdity ^0.5.0;

// Congress.sol
import "./Owned.sol";

contract Congress is Owned, TokenRecipient {
   //...
}

Struct Names

− Use CapWords Style pke SmartCoin.

Event Names

− Use CapWords Style pke Deposit, AfterTransfer.

Function Names

− Use mixedCase Style pke initiateSupply.

Local and State variables

− Use mixedCase Style pke creatorAddress, supply.

Constants

− Use all capital letters with underscore to seperate words pke MAX_BLOCKS.

Modifier Names

− Use mixCase Style pke onlyAfter.

Enum Names

− Use CapWords Style pke TokenGroup.