Intermediate concepts
This chapter will go a bit faster than the previous ones.
We're going to be covering an important part of smart contract development: cross-contract calls.
Các cross-contract call
A cross-contract call is when a smart contract calls another smart contract. For instance, if alice.near
calls contract A, and contract A makes a call to contract B.
NEAR has asynchronous transactions, and some cross-contract calls will have callbacks in order to determine the result of the call. This works a bit different from other blockchains, as we'll explain more in this chapter.
Access keys
Last chapter covered access keys, and we implemented a login system where a user "logs in" by adding a function-call access key to their account which is tied to the crossword puzzle dApp.
Login is a common use case for access keys, but let's think bigger!
Remember the two (smaller, gray) function-call access keys from the keychain illustration?
![A keychain with three keys. A large, gold key represents the full-access keys on NEAR. The two other keys are gray and smaller, and have detachable latches on them. They represent function-call access key. Art created by alcantara_gabriel.near](/vi/assets/images/keys-cartoon-good--alcantara_gabriel.near--Bagriel_5_10-25f5521a242db4d310be7de1dd937aa2.png)
Notice that they have a clasp to make them removable.
While it's unlikely you'll want to give another person a full-access key, there are times when you could give a function-call access key to another person or make it public. Vì sao? This can help enable a smooth onboarding experience, as we'll do soon.
Completed project
Here's the final code for this chapter:
https://github.com/near-examples/crossword-tutorial-chapter-3