Example: Guest Book

Let's explore the successful NEAR project Guestbook together! See below the elements of the project.

There are 2 main folders in the project:

• assembly contains the smart contract and tests
• src contains the application’s UX and tests

There is another folder to be aware of:

• neardev contains contract account details

Note: We will not focus on the “src folder” which is the frontend of this dApp.

Contract Data Model: assembly/model.ts

PostedMessage is a serializable class with three attributes: 

• premium to flag messages with attached NEAR tokens
• sender to track the signer of the guest book message
• text to hold the guest book message

Messages is a collection of guest book messages stored as a PersistentVector of PostedMessage objects.

Note: @nearBindgen marks the class as serializable.

Contract Behavior: assembly/main.ts

MESSAGE_LIMIT is used to avoid unbounded calls (ie. potentially expensive) to retrieve guest book messages from storage.

Two public functions are exposed on the contract: 

• addMessage()
• getMessages()