Quick Guide To Solidity Contracts
In this article, we will explore Solidity contracts, including their structure, data types, functions, and modifiers.
We will also discuss best practices for writing secure and efficient Solidity code and introduce some popular tools and frameworks for Solidity development.
Solidity Contracts
Solidity contracts encapsulate data and functions and represent objects or entities in the blockchain network.
There are several properties of Solidity contracts that make them unique from traditional software programs:
Properties | Overview |
Address | Each Solidity contract has its own blockchain address. An address is used to identify a contract on the network and interact with it. |
State Variables | Using state variables in Solidity, contracts can store data on the blockchain. There are various types of state variables in a contract, including integers, booleans, strings, arrays, and more. State variables are declared at the top level of the contract. |
Functions | An external account or another contract can call the functions defined in Solidity contracts. A function modifies the state variables of a contract, performs calculations, and interacts with other contracts on the network. |
Events | In contracts, events can be generated to notify external accounts or applications about important state changes. Typically, events are used for logging purposes or to initiate off-chain processes. |
Modifier | A modifier restricts access to certain functions or operations within a Solidity contract. The purpose of these functions is to enforce permissions, validate inputs, and ensure that certain conditions are met before executing them. |
Inheritance | Inheritance is a key feature of Solidity contracts, which allows developers to reuse code and functionality across multiple contracts by inheriting from one another. |
Visibility Quantifiers
A visibility quantifier controls the accessibility of functions and state variables within a Solidity contract.
Solidity provides four visibility quantifiers:
Quantifiers | Overview |
Public | Public variables and functions can be invoked from anywhere, within or outside the contract. |
Private | Private functions and state variables can only be accessed within a contract they are declared in. |
Internal | Internally accessible functions or variables are only accessible from within the contract or from its descendants. |
External | External functions cannot be called from within a contract, only from outside. In addition to creating interfaces for interacting with other contracts, external functions also allow public access to certain features. |
Public Quantifiers
The public state variables and functions can be invoked from the parent contact (where it is created in) or from any other contract.
The following example shows the working of public quantifiers:
Example:
Private Quantifiers
The user has the access of private state variables and functions restricted to the contract they are initialized in.
The given example illustrates the working of Private state variables and functions:
Example:
Internal Quantifiers
The internal functions and state variables are accessible from the parent class as well as from the inherited contract but not from the external contracts.
The following code illustrates the working of the Internal quantifier:
Example:
External Quantifiers
The external keyword restricts the function from being accessed in the parent contract (where it was initialized) .
There is no way to make the state variables as external.
If we want to access the external functions inside the parent contract we can use the keyword this to fulfill our requirement.
The example below shows the calling of external functions and its exceptions:
Example:
Example:
Importance of Solidity Visibility Quantifiers
A solidity visibility quantifier’s importance lies in their ability to help you create smart contracts that are secure, modular, and maintainable.
When you choose the right quantifier for each function and variable, your contracts can be accessed only by the necessary parties.
By doing so, you will minimize the risk of vulnerabilities and attacks, as well as improve the readability and structure of your code.
It is crucial, for example, to declare a function private in order to prevent any other contracts or external entities from gaining access to the logic stored within that function, thus reducing the potential for unauthorized manipulation or exploitation.
Additionally, declaring a function external can be beneficial in optimizing gas usage because only outside calls will be allowed to invoke the function. In this way, the need for unnecessary state changes is eliminated.
Solidity visibility quantifiers can help you write more modular and maintainable code. Quantifiers enables you and other developers to better understand the purpose and functionality of a given contract by indicating a function’s intended use and accessibility.
This will facilitate the development of smart contracts that are more complex and interoperable.