Solidity Concepts for Contract Development BDC Practice Questions (Page 4)

Questions 16–20

1. 16application · medium

   A developer is writing a withdraw function for a crowdfunding contract. The contract holds Ether collected from many contributors. The function must refund a caller's contribution and then update the caller's balance to zero. Which implementation correctly applies the checks-effects-interactions pattern?

   • AUse require(msg.sender.send(amount)); then set balance[msg.sender] = 0;
   • BSet balance[msg.sender] = 0; then call msg.sender.call{value: amount}("");
   • CUse transfer(amount) and then set balance[msg.sender] = 0;
   • DCall msg.sender.call{value: amount}(""); then set balance[msg.sender] = 0;
   Reveal Solution Discussion Select an answer first
2. 17foundation · easy

   What is the purpose of an interface in Solidity?

   • ATo provide a default implementation for functions
   • BTo define a contract's external function signatures without implementation
   • CTo enforce access control on functions
   • DTo store state variables and constants
   Reveal Solution Discussion Select an answer first
4. 18foundation · easy

   Which Solidity construct is used to define a custom data type that groups multiple related variables under a single name?

   • AArray
   • BStruct
   • CEnum
   • DMapping
   Reveal Solution Discussion Select an answer first
5. 19foundation · easy

   Which data location is the default for complex types like arrays and structs when declared as state variables in Solidity?

   • Amemory
   • Bcalldata
   • Cstorage
   • Dstack
   Reveal Solution Discussion Select an answer first
6. 20foundation · easy

   Which Solidity control structure is used to execute a block of code repeatedly while a condition remains true?

   • Afor
   • Bif-else
   • Cwhile
   • Dswitch
   Reveal Solution Discussion Select an answer first