The following question has been asked on Telegram:
Hi, how can i return a message to the sender? Like a ‘raise’ but in a case where’s no error
The following question has been asked on Telegram:
Hi, how can i return a message to the sender? Like a ‘raise’ but in a case where’s no error
In Tezos smart contracts, there isn’t a direct “return mechanism” for entrypoints like the raise
statement used in error handling. However, there are several alternatives depending on your requirements:
1. On-chain views:
On-chain views are similar to entrypoints but are read-only. They are defined using the @sp.onchain_view
decorator. These views are useful for retrieving information from the contract without altering its state.
For instance, to get an administrator from a contract:
@sp.onchain_view()
def get_administrator(self):
return self.data.administrator
They can be called using sp.view(view_name, contract_address, value, t) -> sp.option[t]
.
For example:
@sp.entrypoint(self)
def do_something(self, address):
# `address` is the address of the contract
# onto which we call `get_administrator`.
is_administrator = sp.view("get_administrator", address, (), sp.bool).unwrap_some()
On-chain views can also be called off-chain.
2. Events:
Events in Tezos are mechanisms to notify off-chain systems of occurrences within the contract. They are particularly useful for tracking contract activities in indexers or explorers but are not accessible to on-chain code.
Example of emitting an event:
sp.emit(event_name, event_data)
For more details, check SmartPy’s documentation on events.
3. Callback:
thanks!
Is possible to handle event in scenario?