Use assert and raise to check inputs and validate state.
When an error occurs, it will halt the entire function call, undoing any changes.
You will still need to pay gas for the failed transaction.
# pragma version ^0.4.0
x: public(uint256)
owner: public(address)
@deploy
def __init__():
self.owner = msg.sender
@external
def test_assert(x: uint256):
assert x >= 1, "x < 1"
# self.x will not be updated if there is an error from line above
self.x = x
@external
def test_raise(x: uint256):
# same check as above using "raise"
if x <= 1:
raise "x < 1"
self.x = x
@internal
def _test_error_bubbles_up(x: uint256):
assert x >= 1, "x < 1"
self.x = x
@external
def test_error_bubbles_up(x: uint256):
self._test_error_bubbles_up(x)
# self.x = 123 will not be executed if there is an error
# from function above
self.x = 123
@external
def set_owner(owner: address):
assert msg.sender == self.owner, "!owner"
assert owner != empty(address), "owner = zero"
self.owner = owner
