Fundamentals of programming smart contracts TON (FreeTON)

Before we start writing our token and then the smart contract system, let's take a quick overview of the important elements of smart contracts for FreeTON.

In the previous article Hello Word, a smart contract for TON (FreeTON), we looked at the very beginning of working with FreeTON and HelloWorld smart contracts.

The structure of this article:

1. Number types int and uint, pure-functions and event (events): let's write a calculator on the blockchain;

   
   
   
   
   

2. Structures and arrays: smart contracts as a database;

   
   
   
   
   

3. Hash tables: mapping;

   
   
   
   
   

4. Public keys and require.

   
   
   
   
   

: tvm.accept(); -.

int ( ) uint ( ). , : int8, int16, uint128. int uint - int256 uint256. - .

- . calc, 3 uint-: 2 - , . calc pure, , , -, , .

, - , - .

pragma ton-solidity >= 0.35.0;
pragma AbiHeader expire;

contract HelloCalc {

    event UnknownOperator(uint op);

    function calc(uint a, uint b, uint op) public pure returns (uint) {
        tvm.accept();
        
        if(op == 1) {
            return a + b;
        } else if(op == 2) {
            return a - b;
        } else if(op == 3) {
            return a * b;
        } else if(op == 4) {
            return a / b;
        } else if(op == 5) {
            return a % b;
        } else if(op == 6) {
            return a ** b;
        }else {
            emit UnknownOperator(op);
            return 0;
        }
    }
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

(event) - , , , , , 0 , , .

( ) -, , , -. , - blockchain, - blockchain . - blockchain.

pragma ton-solidity >= 0.35.0;
pragma AbiHeader expire;

contract HelloUser {

    event NewUser(uint id);
    
    struct User {
        uint weight;
        uint balance;
    }

    User[] users;

    function AddUser(uint w, uint b) public {
        tvm.accept();
        users.push(User(w, b));
        emit NewUser(users.length - 1);
    }

    function GetUser(uint id) public view returns (uint w, uint b) {
        tvm.accept();
        w = users[id].weight;
        b = users[id].balance;
    }
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

User , 2 uint: . , , , . push, - NewUser.

GetUser: returns, . pure view.

-: mapping

, (User) ( , ) . mapping. , , , , . , , .

mapping :

contract HelloToken {

    event TokenCreated(uint owner, uint tid);
    
    struct Token {
        string name;
        string symbol;
    }

    Token[] tokens;

    mapping (uint => uint) accounts;

    function NewToken() public {
        tvm.accept();

        tokens.push(Token("", ""));
        accounts[tokens.length-1] = msg.pubkey();
        emit TokenCreated(msg.pubkey(), tokens.length-1);
    }

   function GetTokenOwner(uint tid) public view returns (uint) {
       tvm.accept();
       return accounts[tid];
   }

   function GetTokenInfo(uint tid) public view returns (string _name, string _symbol) {
       tvm.accept();
       _name = tokens[tid].name;
       _symbol = tokens[tid].symbol;
   }

 function SetTokenInfo(uint tid, string _name, string _symbol) public {
       require(msg.pubkey() == accounts[tid], 101);
       tvm.accept();
       tokens[tid].name = _name;
       tokens[tid].symbol = _symbol;
   }
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

require

- , , - , ( ). : , , value TON Crystal . . - API msg.pubkey(). NewToken() accounts[tokens.length-1] = msg.pubkey(); ID accounts , , tokens. SetTokenInfo() , , . tid accounts . .

Aspects were described here for readers studying the topic of FreeTON smart contracts "from scratch", and in the next articles we will start creating our own token.