Solidity Concepts for Contract Development BDC Practice Questions (Page 6)

Questions 26–30

1. 26foundation · easy

   Which statement is best suited for validating user inputs and external conditions in a Solidity function?

   • Arequire
   • Brevert
   • Cassert
   • Dif-else
   Reveal Solution Discussion Select an answer first
2. 27foundation · easy

   Which common vulnerability occurs when a contract makes an external call before updating its own state, allowing the called contract to re-enter and exploit the original contract?

   • APhishing
   • BDenial of service
   • CReentrancy
   • DInteger overflow
   Reveal Solution Discussion Select an answer first
4. 28application · medium

   A developer is writing a function that allows users to deposit Ether into a contract. The function should be able to receive Ether and update the user's balance. Which function declaration is correct?

   • Afunction deposit() external payable { balances[msg.sender] += msg.value; }
   • Bfunction deposit() public payable { balances[msg.sender] += msg.value; }
   • Cfunction deposit() internal payable { balances[msg.sender] += msg.value; }
   • Dfunction deposit() external { balances[msg.sender] += msg.value; }
   Reveal Solution Discussion Select an answer first
5. 29foundation · easy

   Which function visibility modifier allows a function to be called only from within the contract where it is defined and from derived contracts?

   • Aexternal
   • Binternal
   • Cprivate
   • Dpublic
   Reveal Solution Discussion Select an answer first
6. 30foundation · easy

   Which Solidity type is used to define a custom type with a finite set of named values, such as 'Pending', 'Shipped', 'Delivered'?

   • AArray
   • BMapping
   • CEnum
   • DStruct
   Reveal Solution Discussion Select an answer first