A Beginner's Guide to Solidity: Understanding the Fundamentals of the Ethereum Smart Contract Language

Just a decade ago, it was difficult to imagine a world where you could create unique digital assets that could run on their own. A world where code takes the place of trust and there are no middlemen. Today, this world is no longer a figment of our imagination; it's the world of smart contracts and blockchain. And Solidity is the language that makes this world possible.

Solidity is the programming language that enables smart contract creation on the Ethereum network. As with any other language, it has its own grammar, syntax, and organization. But unlike other programming languages, Solidity opens up an entirely new universe of possibilities.

In this article, I will write about Solidity, the language that is revolutionizing the way we interact with the digital world. From understanding the basics of the language to learning about the unique components that make it stand out, this beginner's guide will give you a solid foundation in Solidity. So, whether you're new to programming or just looking to expand your skillset, read on till the end.

Basic Introduction

Solidity is a high-level, contract-oriented language used to build smart contracts on the Ethereum Virtual Machine (EVM). It was influenced by C++, Python, and JavaScript and shares syntax and programming concepts with these languages.

Key Components:

Logic: Solidity allows for the use of if-else statements, for and while loops, and other logical operators like and, or, and not.

Scope: Solidity has global, contract and function-level scopes. Each variable or function has a specific scope in which it can be accessed or modified.

Patterns: Solidity has common design patterns that can be used to write smart contracts such as the Open-Close Principle and the Pull Payment pattern.

Functions: Solidity supports both internal and external functions. Internal functions can only be called by other functions within the same contract, while external functions can be called by any contract or externally.

Structures: Solidity allows for the creation of custom data structures such as structs and arrays.

Libraries: Solidity supports the use of libraries, which are reusable blocks of code that can be called by multiple contracts.

Let's get our hands dirty and explain each of these key components using code examples and explanations.

The following is an example of logic written in Solidity.

function checkAge(uint age) public pure returns (bool) {
    if (age >= 18) {  // this line checks if the input age is greater than or equal to 18
        return true;   // if the above condition is met, it returns true
    } else {
        return false;  // if the above condition is not met, it returns false
    }
}

This code defines a function called checkAge that takes in an input of type uint (unsigned integer) called age.

The function has the visibility public and pure which means that it does not read or modify the state variables and returns the values only using the parameters passed to it or local variables present in it. It can be called externally without any side effects during compilation.

The function also returns a boolean value, true if the age is greater than or equal to 18 and false otherwise.

Easy enough, right? Now let's write some Solidity scope in the following example.

contract Enitandev {
    uint private age = 25;  // this line declares a private variable of type uint called age and assigns it the value 25

    function getAge() public view returns (uint) {  // this function is public and read-only
        return age;  // this line returns the value of the private variable age
    }
}

_Note: Local variables have a scope that is limited to the function in which they are defined, whereas state variables can have three types of scopes.

Public: Public state variables can be accessed both internally and via messages. An automatic getter function is generated for a public state variable.

Internal: Internal state variables can only be accessed internally from the current contract or a contract derived from it.

Private: Private state variables can only be accessed internally from the current contract in which they are defined, not from the derived contract._

The above code defines a contract called Enitandev. It has a private variable age of type uint that is only accessible within the contract.

The contract also defines a getAge function that has public and view (read-only) visibility so it can be called externally. The function then returns the value of the private variable age.

Now let's move on to patterns in Solidity.

Note: Design patterns are reusable, traditional approaches to addressing recurrent design issues. Transferring funds from one address to another is an example of a common design pattern in Solidity as demonstrated in the example below.

contract Token {
    mapping(address => uint) public balanceOf;  // this line creates a public mapping called balanceOf that maps addresses to uint values

    function approve(address _spender, uint _value) public {  // this function is public
        require(balanceOf[msg.sender] >= _value && _value > 0);  // this line checks if the msg.sender's balance is greater than or equal to the input _value and that _value is greater than 0
        approve[_spender] = _value;  // this line sets the approved value for the input address _spender to the input _value
    }

    function transfer(address _to, uint _value) public {  // this function is public
        require(balanceOf[msg.sender] >= _value && _value > 0);  // this line checks if the msg.sender's balance is greater than or equal to the input _value and that _value is greater than 0
        require(approve[msg.sender][_to] >= _value); // this line checks if the approved value for msg.sender to send to _to is greater than or equal to _value
        balanceOf[msg.sender] -= _value;  // this line subtracts _value from the msg.sender's balance
        balanceOf[_to] += _value;  // this line adds _value to the balance of address _to
    }
}

The above code defines a contract called Token. It has a public mapping called balanceOf that maps addresses to uint values.

The contract also has two functions, approve and transfer, that are both public. The approve function takes in an address _spender and a uint _value as input.

The function first checks if the msg.sender's balance is greater than or equal to the input _value and that _value is greater than 0. If this condition is met, it sets the approved value for the input address _spender to the input _value.

The transfer function takes in an address _to and a uint _value as input. The function first checks if the msg.sender's balance is greater than or equal to the input _value and that _value is greater than 0. It also checks if the approved value for msg.sender to send to _to is greater than or equal to _value.

If all of these conditions are met, it subtracts _value from the msg.sender's balance and adds _value to the balance of address _to.

Now Let's talk functions in Solidity.

contract Enitandev {
    function internalFunction() internal {
        // code here
    }

    function externalFunction() public {
        // code here
    }
}

This above code defines a contract called Enitandev. It has two functions, internalFunction and externalFunction. The internalFunction function has internal visibility, meaning it can only be called by other functions within the same contract. The externalFunction function has public visibility, meaning it can be called by any contract or externally.

Next up? Structures

In Solidity, a struct is a creative data structure format in which variables of various data types can be packaged into one variable or a custom-made type. See the example below.

struct Person {
    string name;
    uint age;
}

contract Enitandev {
    Person[] public people;

    function addPerson(string memory _name, uint _age) public {
        people.push(Person(_name, _age));  // this line adds a new person to the people array with the input name and age
    }
}

The code above defines a contract called Enitandev. It has a struct called Person which has two fields, name which is a string and age which is a uint.

The contract also has a public variable people which is an array of Person structs. The contract has a function called addPerson which takes in two inputs, a string called _name and a uint called _age.

The function then adds a new person to the people array with the input name and age.

Let's talk about Libraries to wrap up the section on key components.

Solidity libraries are comparable to contracts that contain reusable code. A library contains functions that can be accessed through other contracts. Creating a library and deploying shared code decreases gas costs. Let's demonstrate with an example

library SafeMath {
    function add(uint a, uint b) internal pure returns (uint) {
        require(a + b >= a);  // this line checks that the result of the addition is greater than or equal to a
        return a + b;  // this line returns the result of adding a and b
    }
}

contract Enitandev {
    using SafeMath for uint;  // this line allows the use of the SafeMath library functions for uint type

    uint public total;

    function add(uint a, uint b) public {
        total = a.add(b);  // this line calls the add function from the SafeMath library and assigns the result to the total variable
    }
}

The code defines a library called SafeMath which contains a single function called add. The function takes two inputs, a and b, both of which are unsigned integers (uint).

The function starts with a require statement, which checks that the result of the addition of a and b is greater than or equal to a. This is done as a safety check to ensure that the operation does not result in an overflow or underflow, which can occur when adding large numbers. If the condition is not met, the function will not execute and the require statement will raise an exception.

The function then returns the result of adding a and b using the return statement.

Below the library the contract Enitandev is declared, it has a single state variable called total which is a public variable of type uint.

The contract has a function called add which takes two input variables, a and b of type uint. Inside the function, the total variable is assigned the result of calling the add function from the SafeMath library and passing in a and b as arguments.

The using SafeMath for uint; line allows the contract to use the SafeMath functions with the uint type. This means that instead of calling the library function directly, you can use the . operator to call the function and the library will automatically check for overflow and underflow.

So this code provides a way to use the SafeMath library functions for the uint type and ensure that the operations are done safely and securely.

What can Solidity be used to do?

The scope of what Solidity can achieve depends on the unique use case and contract requirements. HoweverSolidity is commonly used in the following scenarios:

Token creation and management: On the Ethereum blockchain, Solidity is commonly used to create and manage digital assets such as tokens.

Decentralized finance (DeFi): Solidity can be used to develop decentralized financial applications such as lending and borrowing platforms.

Supply Chain Management: Solidity can be used to develop smart contracts that automate supply chain procedures such as tracking the movement of items and maintaining regulatory compliance.

Gaming: Solidity can be utilized to develop decentralized gaming apps such as in-game objects and virtual worlds.

Developer Circles criticize Solidity for what?

Solidity, like any technology, has criticisms. Among the most common ones are:

Complexity: Writing smart contracts in Solidity can be difficult and requires a thorough understanding of the Ethereum environment as well as the contract's specific requirements. Because of this intricacy, it can be challenging for developers to design secure and dependable contracts.

Security: Solidity contracts are immutable, which means that their code cannot be modified once they are deployed. This makes it difficult to repair faults or vulnerabilities identified after deployment, and it has resulted in a number of high-profile smart contract attacks.

Gas costs: Gas fees are incurred while interacting with the Ethereum blockchain, including the deployment and execution of smart contracts. The cost of these fees varies depending on network congestion and contract complexity, making it less accessible to some consumers.

Maturity: Solidity is a new language, and the ecosystem is still developing. As a result, tooling, libraries, and best practices may have limits.

Limited flexibility: Because Solidity is a contract-oriented language, it is not appropriate for implementing all sorts of applications. It is also difficult to manage big amounts of data and conduct complex computations.

Limited Language Features: Solidity lacks some language features seen in more mature languages, such as inheritance, generics, and complicated data structures like sets and maps.

It's important to note that many of these criticisms are related to the current state of the Ethereum ecosystem rather than the language itself, and the ecosystem is continuously evolving and improving. Additionally, many of the criticisms are subjective and depend on the use case, requirements, and the specific project context.

And there you have it folks, a beginner's guide to Solidity that will have you coding like a pro in no time! From understanding the basics of the language to the nitty-gritty details of its unique components, we've covered it all. We've explored the use cases for Solidity and its limitations, and we've provided you with some examples of basic syntax and code.

You're now equipped with the knowledge to start creating your own smart contracts on the Ethereum blockchain. So, whether you're looking to launch your own decentralized application or create a new digital asset, the world of blockchain is waiting for you. Remember to keep learning and experimenting, and always be on the lookout for new and exciting developments in the world of Solidity. Happy coding!