Add Instructions

As mentioned in the instructions and transactions section, Instructions are the basic operational units on Solana. Instructions are commands that can be bundled up together to form Transactions. These transactions can then be executed by a Program to read and/or write data from one or more Accounts. The instructions that form the transaction are executed atomically, or one-by-one in the order in which they were added to form the transaction.

To make instances of polls, and write/modify the data stored in these polls, we will need to write instructions for our program.

Initialising Poll

Instructions in Seahorse are written using functions with the @instruction decorator. Let's add a create_poll instruction to our program:


from seahorse.prelude import *

declare_id('11111111111111111111111111111111')

class Poll(Account):
  ethereum: u64
  solana: u64
  polygon: u64

# Initialises the poll account
@instruction
def create(poll: Empty[Poll], user: Signer):
    poll = poll.init(
        payer=user
    )

From the first look, this may seem a little weird if you've never seen a statically typed language before like TypeScript.

def create_poll(poll: Empty[Poll], user: Signer)

In Python, it is not necessary to declare the type of variables, but in Seahorse its necessary to do so to determine at compile time what account type does the variable belong to.
There are a new account type mentioned here: Empty. This is a Seahorse native account type.
Empty[Poll] indicates that poll is an empty account of type poll. This means that poll has not yet been initialised and has no data stored.

poll = poll.init(
  payer=user
)

In the above codeblock, we are using .init() on the Empty poll account. We use the payer argument to choose the user account to pay for the instruction. For the .init() instruction the signer is required to pay to initialise the account. Solana transactions involve a cost, and the payer account needs to be assigned for the individual instruction which will be debited some SOL when the transaction is processed.

We get back the initialised poll account from .init() which we will use later to modify poll state.

Voting

As of now, we have added an instruction to our program to initialise a poll account. Now its time to add an instruction to let users vote for their favorite blockchain.

Let's add the following code to the poll.py file:


@instruction
def vote(user: Signer, poll: Poll, vote_op: str):
  if vote_op == "eth":
    poll.ethereum += 1
  elif vote_op == "sol":
    poll.solana += 1
  elif vote_op == "pol":
    poll.polygon += 1
  else:
    print("Candidate does not exist")

We add the following as instruction parameters:

user account of type Signer
poll account of type Poll
vote_op enum of type str

For the already-trained in Anchor, the above might look strange as we are essentially adding accounts and other data as instruction parameters together. This is way simpler than Anchor where data and accounts have to be handled differently.

Like Empty, Signer is also an in-built account type available in Seahorse. In any blockchain, users need to sign the transactions to modify state of accounts (write/modify data). In our case as well, for a user to vote for their favorite chain and hence change the state of the account, they will have to sign a transaction. Signer represents the type of account user which will sign the transaction which will contain given intruction (create_poll).
The rest of the instruction is pretty straight-forward as we are simply incrementing the dedicated chain fields in the poll account depending on the type of vote_op provided.
As poll is essentially a Python object, the individual fields: ethereum, solana and polygon can be fetched simply by . notation: poll.solana.
print(): Seahorse print statements are pretty much the same as Python print statements, and you can use them to print debug your programs. Under the hood, they get translated to an equivalant call to the Solana logger.

Voila, we are done with our first Solana Program thanks to Seahorse! Our program looks like this:


# poll
# Built with Seahorse v0.2.4
#
# On-chain, persistent Poll!

from seahorse.prelude import *

declare_id('11111111111111111111111111111111')

class Poll(Account):
    ethereum: u64
    solana: u64
    polygon: u64

@instruction
def create(poll: Empty[Poll], user: Signer):
    poll = poll.init(
        payer=user
    )

@instruction
def vote(user: Signer, poll: Poll, vote_op: str):
    if vote_op == "eth":
        poll.ethereum += 1
    elif vote_op == "sol":
        poll.solana += 1
    elif vote_op == "pol":
        poll.polygon += 1

Seahorse University

Add Instructions

Initialising Poll

Voting