State on the Chain
Access control, errors & money
Lesson 3 of 5
Modifiers factor out permission checks, custom errors replace strings, and payable functions let a contract hold ETH. Revert rolls it all back, and the withdraw pattern keeps the money safe.
What you'll learn
- Write an onlyOwner modifier and a custom error and explain what each costs
- Accept ETH with payable and pay it out with the pull-based withdraw pattern
- Show that a revert rolls back state and refunds msg.value
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