Interfaces in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an interface in blockchain smart contracts?

An interface in blockchain smart contracts is a way to define a set of functions that a contract must implement, without providing the function bodies. It acts like a contract blueprint.

beginner

Why use interfaces in smart contracts?

Interfaces help ensure that different contracts follow the same rules and can work together. They make code easier to understand and maintain by defining clear function signatures.

beginner

Can an interface contain function implementations in blockchain smart contracts?

No, interfaces only declare function signatures without any implementation. The actual code must be written in the contract that implements the interface.

intermediate

How does a contract implement an interface?

A contract implements an interface by including the interface name and providing code for all the functions declared in the interface.

intermediate

Give a simple example of an interface in Solidity.

Example:
interface IExample {
  function getValue() external view returns (uint);
  function setValue(uint _value) external;
}
This defines two functions that any contract implementing IExample must have.

What does an interface in blockchain smart contracts define?

A Function signatures without implementation

B Complete function code

C Storage variables only

D Events only

Interfaces only declare function signatures without any code.

Can a contract implement multiple interfaces?

A Only if interfaces have no functions

B No, only one interface is allowed

C Yes, a contract can implement many interfaces

D Only if interfaces are from the same file

Contracts can implement multiple interfaces to combine different function sets.

What happens if a contract does not implement all functions of an interface it claims to implement?

A Interface is ignored

B Contract deploys but fails at runtime

C Functions are auto-generated

D Compilation error

The compiler requires all interface functions to be implemented, or it throws an error.

Which keyword is used to declare an interface in Solidity?

A interface

B contract

C library

D abstract

The 'interface' keyword declares an interface in Solidity.

Interfaces in smart contracts help mainly with:

A Storing data

B Standardizing function signatures

C Executing transactions

D Mining blocks

Interfaces standardize function signatures so contracts can interact predictably.

Explain what an interface is in blockchain smart contracts and why it is useful.

Think of an interface as a promise about what functions a contract will have.

Describe how a contract implements an interface and what happens if it misses a function.

Implementation means writing the actual function code for the interface's declared functions.