Exercise: Modifiers

In this short exercise, we'll practice using function modifiers in smart contracts and update the Ownable smart contract in the process.

The onlyOwner modifier

For this exercise, we'll implement a new modifier called onlyOwner that'll enforce that a particular method is only called by the owner of the smart contract.

The starter code for this exercise can be found on this GitHub page.

To implement the new modifier, we need to make two changes that we’ve marked with TODO comments:

• Implement the new onlyOwner modifier that enforces that a method can only be called by the contract’s owner.

• Apply the new modifier on the transferOwnership method.

Here are the changes we need to make: