For this exercise, we’re challenging you to build a solution requiring you to use a number of the concepts you’ve learned so far. Have fun and enjoy!

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Contracts

Build a contract that can deploy copies of an address book contract on demand, which allows users to add, remove, and view their contacts.

You’ll need to develop two contracts for this exercise and import at least one additional contract.

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Imported Contracts

Review the Ownable contract from OpenZeppelin. You’ll need to use it to solve this exercise.

You may wish to use another familiar contract to help with this challenge.

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AddressBook

Create an Ownable contract called AddressBook. It includes:

  • A struct called Contact with properties for:
    • id
    • firstName
    • lastName
    • a uint array of phoneNumbers
  • Additional storage for contacts
  • Any other necessary state variables

It should include the following functions:

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Add Contact

The addContact function should be usable only by the owner of the contract. It should take in the necessary arguments to add a given contact’s information to contacts.

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Delete Contact

The deleteContact function should be usable only by the owner and should delete the contact under the supplied _id number.

If the _id is not found, it should revert with an error called ContactNotFound with the supplied id number.

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Get Contact

The getContact function returns the contact information of the supplied _id number. It reverts to ContactNotFound if the contact isn’t present.

Question

For bonus points (that only you will know about), explain why we can’t just use the automatically generated getter for contacts?

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Get All Contacts

The getAllContacts function returns an array with all of the user’s current, non-deleted contacts.

You shouldn’t use onlyOwner for the two get functions. Doing so won’t prevent a third party from accessing the information, because all information on the blockchain is public. However, it may give the mistaken impression that information is hidden, which could lead to a security incident.

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AddressBookFactory

The AddressBookFactory contains one function, deploy. It creates an instance of AddressBook and assigns the caller as the owner of that instance. It then returns the address of the newly-created contract.

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Submit your Contract and Earn an NFT Badge! (BETA)

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Hey, where’d my NFT go!?

Testnets are not permanent! Base Goerli will soon be sunset, in favor of Base Sepolia.

As these are separate networks with separate data, your NFTs will not transfer over.

Don’t worry! We’ve captured the addresses of all NFT owners on Base Goerli and will include them when we release the mechanism to transfer these NFTs to mainnet later this year! You can also redeploy on Sepolia and resubmit if you’d like!