About This Solidity_Tutorial

This is a Solidity tutorial for beginners which uses an Proposal Smart Contract to teach Solidity Smart Contract Development basics. To understand the course, you need basic Solidity knowledge including:

• Function Modifiers
• Data types
• Function Types
• Storage, Memory and Calldata

Also, this tutorial is created to be easy to follow with, so you can also code yourself and practise.

Commonly Asked Questions and Answers in Solidity

1. What is Solidity?

Answer: Solidity is a statically-typed programming language designed for writing smart contracts on the Ethereum blockchain platform.

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2. What is the difference between view, pure, and payable function modifiers?

Answer:

• view: This function will not modify state variables and is only used for viewing data.
• pure: Similar to view, but pure functions also can't read the state.
• payable: This function can receive Ether during its execution.

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3. What is msg.sender?

Answer: msg.sender is a special variable that holds the address of the person or contract that initiated the current function call.

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4. How do you import a library in Solidity?

Answer: Use the import statement to import a library. E.g., import "@openzeppelin/contracts/token/ERC20/IERC20.sol";.

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5. What is the storage and memory data location?

Answer:

• storage: Persistent storage on the blockchain, but changes are very costly in terms of gas.
• memory: Temporary storage, cheaper but only available during the execution of a function.

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6. What are events and how are they used?

Answer: Events allow logging to the Ethereum blockchain. These logs can be easily accessed from a frontend application and are an effective way to "return" data from transactions, which otherwise don't yield a return value.

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7. How do you write upgradable smart contracts?

Answer: Upgradable smart contracts often employ a proxy pattern. The logic and data are separated, and the logic can be changed without affecting the data.

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8. What are mappings?

Answer: Mappings are hash tables that exist in the storage of a contract. They map keys to values, providing quick look-up capabilities.

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9. What is the difference between public and external function visibility?

Answer:

• public: Can be called both internally and externally.
• external: Can only be called externally, i.e., from outside the current contract.

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10. How do you handle re-entrancy attacks?

Answer: To prevent re-entrancy attacks, you can use the Checks-Effects-Interactions pattern and make sure to not call external contracts until you've done all the internal work you need to do.

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11. What is the gas limit and gas price?

Answer:

• Gas limit: The maximum amount of gas the user is willing to spend on a transaction.
• Gas price: The amount of Ether the user is willing to spend per unit of gas.

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12. How do you debug a Solidity smart contract?

Answer: You can debug using tools like Remix, Hardhat, or Truffle Debugger, which allow you to step through each line of your Solidity code.

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13. How do I interact with a deployed contract?

Answer: You can interact with a deployed contract through Web3.js or Ethers.js libraries in a JavaScript environment, or directly through a Solidity interface in a contract-to-contract call.

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14. What are Solidity modifiers?

Answer: Modifiers are function decorators that can be used to change the behavior of functions in a declarative way.

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15. How do you manage different versions of Solidity?

Answer: You specify the compiler version with the pragma solidity ^x.y.z; statement. It’s also possible to specify a range of versions.

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These are just a few of the commonly asked questions in the world of Solidity. I hope you find this helpful!