Solidity

Solidity for EVM compatible smart contracts.

• Solidity Lang
• Solidity by Example
• Eth.build
• Speed Run Ethereum

tip

master the remix debugger

REPL

• Chisel

Learning Path

• Interview challenges

Fundamentals

Copy examples into Scaffold Eth then play around.

Task	Done	Notes
Primitive Data Types	Y	boolean, uint, int, address
Mappings	T	Document best use cases
Structs	Y	Can written external to a contract and imported
Modifiers	Y	Clean up repetitive code, example auth checks
Events	Y	Cheap for of data storage
Inheritance	Y	Allows multiple
Payable	Y	Allows a method to recieve ether
Fallback	Y	Called when no method exists

Global Variable and MSG

Official Docs

Explanatory Articles:

• What you need to know!

Random Numbers

No easy solution with Smart Contracts.

Oracles exist to solve this problem.

Mappings

Good for single value lookups.

Use instead of arrays to hold sets of data to save time and gas.

• Keys are not stored
• Values are not iterable
• Default value of type is returned

Default values, provides challenges.

Reference Types

Name	Rules	Use When
Fixed Array	Single type of element; Size cannot change
Dynamic Array	Single type of element; Size can change
Mapping	Collection of entities
Struct	Structure of an entity

Testing Solidity

• Unit Testing Tips
• Testing Smart Contracts
• Testing In Depth
• Test Case Practice

Packages

• Solidity Coverage - from colony.io

Javascript Bridge

• Cannot communicate nested dynamic arrays
• Strings in Solidity are dynamic arrays

Context

• Developer Roadmap

Diagrams

• Explanatory Diagrams | |

Resources

• Solidity Lang
• Solidity GitHub
• Solidity by Example
• Speed Run Ethereum

Questions

When on-chain randomness is impossible without oracles, how do you design a prediction game that is both fair and trustless?

• The Mappings table notes that values are not iterable and default values cause challenges — what patterns prevent silent bugs from uninitialized mappings in production contracts?
• The Fallback function is called when no method exists — how does this interact with the upgrade patterns needed as smart contract logic evolves?
• Given that strings in Solidity are dynamic arrays with a costly JavaScript bridge, when is it better to store data off-chain and reference it on-chain by hash?