Yashotantra Academy logo
← Solidity theorytheory 0/50 · 0%
level 1
Curious · 0 XP
streak
0d
perfect
0
badges
0

100 XP to Apprentice

Interfaces · easy

14. Events and logs

How contracts talk to the outside world.

1 min read3 questionsup to 50 XPtopic 14/50

Read in another language

AI translates the explanation and quiz text while preserving code and answer scoring.

Events write to the transaction log, which contracts cannot read but indexers, wallets and front-ends can. Up to three parameters may be `indexed`, becoming searchable topics.

solidity
event Staked(address indexed user, uint256 amount);

function stake(uint256 amount) external {
    bal[msg.sender] += amount;
    emit Staked(msg.sender, amount);
}

Logs are much cheaper than storage, so emit an event for every state change you would want to reconstruct later.

How to study this topic

  1. 1. Read the explanation once end to end, skipping the code.
  2. 2. Re-read the code snippets and say out loud what each line does.
  3. 3. Answer the quiz without scrolling back — that is the real check.
  4. 4. Read every explanation, even for the answers you got right.

Scoring

  • · Up to 30 XP from quiz accuracy.
  • · +15 XP for a perfect first attempt.
  • · +5 XP while a 3-day streak is running.
  • · 75% or higher marks the topic complete.

Check your understanding

  1. 1. Can a contract read past events?

  2. 2. How many parameters can be indexed?

  3. 3. Why emit events?

Badges

First light
Pass your first topic
Sharp shooter
3 perfect first-try quizzes
On a roll
Study 3 days in a row
Week warrior
Study 7 days in a row
Grinder
Earn 500 XP
Deep diver
Earn 1500 XP