The simplest ethereum smart contract

Hi everyone! Today I want to speak about writign the simplest smart contract for ethereum blockchain.

Currently I’m working as a developer at the Bonum company. The most interesting thing I did there was writing a bunch of code for the ICO process. If you don’t believe me, you can check some code. I’m not a liar :)

So, idea of this article is about writing the simplest possible smart contract.

A bit of theory

I won’t talk too much about theory, you only need to know, that Ethereum is a global distributed virtual machine and you can run some code on it.

A bit of code

So, why don’t we write a simple Hello World program?

pragma solidity ^0.4.19;
 
contract HelloWorld {
    
    function sayHello() public view returns (string) {
        return "Hello, world!";
    }
    
}

We’ve done. That’s all. contract is some kind of classes for Ethereum (It’s not the absolute truth, but for the first step that explanation is ok).

A bit of code #2

For the second example we’ll create a contract with changing it’s state.

pragma solidity ^0.4.19;

contract Speaker {    
    string phrase;

    function sayPhrase() public view returns (string) {
        return phrase;
    }
    
    function setName(string newPhrase) public {
        phrase = newPhrase;
    }
}

Here is it. In that contract we set phrase and can ask the contract to say it. If we make phrase public, we will be able to read it’s state without getter. But we still need the setter, because of Ethereum realisation’s features.

Conclusion

That’s all. I’ll be happy, If this article helps you