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How to create, deploy and manage solidity contract on blockchain

Blockchain is the hottest technology now days, and smart contracts are the business logic or a protocol according to which all the transactions on a Blockchain happen.

We are talking about develop and deploy a Smart contract on Ethereum blockchain, today.

So I am assuming that you are familiar with the smart contracts. You knows what is smart contract and how it’s working.

I am taking a small example to store and read a value on blockchain by smart contract.


pragma solidity >=0.4.16 <0.7.0;

contract SolidityStorage {
    uint256 storedData = 5;

    function set(uint256 _x) public {
        storedData = _x;
    }

    function get() public view returns (uint256) {
        return storedData;
    }
}

This is a basic example to store a value on blockchain.
Let’s explain this example.

pragma solidity >=0.4.16 <0.7.0;

This is the compiler version of the solidity. You can change it to your requirements. Solidity is the language which use to create smart contract for ethereum.

contract SolidityStorage

This is denote the our contract name. “contract” is keyword to define a contract just like “class” in oops.

 uint256 storedData = 5;

This is the variable to store a value in it just like other programming languages. uint256 is the variable type.

What is uint256?

Obviously, this question must be arising in your mind. This is just a type of int variable but this have its own definition.
U - unsigned (meaning this type can only represent positive integers, not positive and negative integers)
INT - integer
256 - 256 bits in size

function set(uint256 _x) public {
        storedData = _x;
    }



This is function which we use to change the value of store. 

function get() public view returns (uint256) {
        return storedData;
    }


This is the last in this contract. This function is use to return the stored value in your smart contract.


Deploy and contract interaction


I am using the eth-brownie for deploying the smart contract on blockchain.

Setup your project according to this package. Read the documentation carefully.

Create a file deploy.py in scripts folder - 

from brownie import SolidityStorage, accounts

def main():
    token = accounts[0].deploy(SolidityStorage)



Now you have completed your smart contract development.

Now we start the smart contract execution. Just run  following commands.

brownie compile

brownie deploy.py

Congratulations. Your first smart contract is deployed on blockchain.
 
You can change in you main function to test the values.



def main():
    token = accounts[0].deploy(SolidityStorage)
    storedValue = token.get()
    # to set new value
    token.set(10)

   

token.set(10), this will change the default value 5 to 10 in stored contract.

So this is the just so basic example. You can modify this according to your requirements and develop a smart business logics on the blockchain with using the smart contract.

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