Solidity

Question 1

Is Solidity statically or dynamically typed?

Answer 1

It is statically typed, which means that types are known at compilation.

Question 2

What is the equivalent to the Java “Class” in Solidity?

Answer 2

It’s the Contract.

Question 3

What is an instance of a contract?

Answer 3

An instance of a contract is the deployed contract on the blockchain.

Question 4

Give me a couple of differences between Java and Solidity.

Answer 4

Solidity supports multiple inheritance but doesn’t support overloading

Question 5

What is the very first thing you must specify in a Solidity file?

Answer 5

The version of Solidity compiler, which is specified as ^0.8.8. It is necessary because it prevents incompatibility errors which can be introduced when compiling with another version.

Question 6

What does a contract consist of?

Answer 6

It consists mainly of storage variables, functions and events.

Question 7

What types of functions are there?

Answer 7

There is a constructor, fallback function, constant functions and functions that modify the contract state.

Question 8

What error will I get if I put multiple contract definitions into a single Solidity file?

Answer 8

It is perfectly fine to put multiple contract definitions into a single Solidity file.

Question 9

What are some ways in which two contracts can interact?

Answer 9

A contract can invoke, create and inherit from another contract(s).

Question 10

What happens when you try to deploy a file with multiple contracts?

Answer 10

The compiler only deploys the last contract in that file and all other contracts are ignored.

Question 11

What if I have a huge project, do I need to keep all my related contracts into a single file?

Answer 11

You can use import statement to import a file, import “./MyOtherContracts.sol”

Question 12

Can I only import local files?

Answer 12

You can also import files using HTTP (even from Github), import “http://github.com/<owner>/<repo>/<path>"</path></repo></owner>

Question 13

What parts is the memory of an EVM divided into?

Answer 13

It is divided into Storage, Memory and Calldata

Question 14

Explain Storage

Answer 14

Think of it as a database. Each contract manages its own Storage variables. It is a key-value datastore (256 bit key & value). The read and write are more costly in terms of gas used per execution.

Question 15

Explain Memory

Answer 15

It is a temporary storage. The data is lost once the execution terminates. You can allocate complext datatypes like arrays and structs.

Question 16

Explain Calldata

Answer 16

It can be thought of as the callstack. It is temporary, non-modifiable, and it stores EVM execution data.

Question 17

What variables are stored in the Storage and Memory areas respectively?

Answer 17

State variables and local variables (wich are references to the state variables) are stored in Storage. Function arguments are located in Memory area.