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CHALLENGE.MD

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Challenge : day 5 🦆

Prerequisites ✅

  • Make sure you've read all the instructions on how to complete the challenges.

  • Follow along with the daily guide.

Coding 🧑‍💻

  • Challenge 1 : Write a function is_anonymous that takes no arguments but returns true is the caller is anonymous and false otherwise.

  • Challenge 2 : Create an HashMap called favoriteNumber where the keys are Principal and the value are Nat.

  • Challenge 3 : Write two functions :

    • add_favorite_number that takes n of type Nat and stores this value in the HashMap where the key is the principal of the caller. This function has no return value.
    • show_favorite_number that takes no argument and returns n of type ?Nat, n is the favorite number of the person as defined in the previous function or null if the person hasn't registered.

  • Challenge 4 : Rewrite your function add_favorite_number so that if the caller has already registered his favorite number, the value in memory isn't modified. This function will return a text of type Text that indicates "You've already registered your number" in that case and "You've successfully registered your number" in the other scenario.

  • Challenge 5 : Write two functions

    • update_favorite_number
    • delete_favorite_number

  • Challenge 6 : Write a function deposit_cycles that allow anyone to deposit cycles into the canister. This function takes no parameter but returns n of type Nat corresponding to the amount of cycles deposited by the call.

  • Challenge 7 (hard ⚠️) : Write a function withdraw_cycles that takes a parameter n of type Nat corresponding to the number of cycles you want to withdraw from the canister and send it to caller asumming the caller has a callback called deposit_cycles()
    Note : You need two canisters.
    Note 2 : Don't do that in production without admin protection or your might be the target of a cycle draining attack.

  • Challenge 8 : Rewrite the counter (of day 1) but this time the counter will be kept accross ugprades. Also declare a variable of type Nat called versionNumber that will keep track of how many times your canister has been upgraded.

  • Challenge 9 : In a new file, copy and paste the functionnalities you've created in challenges 2 to 5. This time the hashmap and all records should be preserved accross upgrades.

  • Challenge 10 (optional) : In autonomy, write a CRUD canister, you can add as much functionnalities as you want, a few examples :

    • Anonymous principal rejection.
    • Cycle functionnality for registration.
    • Admin management.

Note : Only practice challenge 10 if you wish to, this is optional and it will not be taken into account for any ranking.


Good luck 🎉