Error Handling (assert / require / revert / try-catch)

Solidity++ uses state-reverting exceptions to handle errors. Such an exception undoes all changes made to the state in the current call (and all its sub-calls) and flags an error to the caller.

Error propagation through revert and try/catch will be supported in v0.8.1.

assert(bool condition)

causes a Panic error and thus state change reversion if the condition is not met - to be used for internal errors.

require(bool condition)

reverts if the condition is not met - to be used for errors in inputs or external components.

require(bool condition, string memory message)

reverts if the condition is not met - to be used for errors in inputs or external components. Also provides an error message.

revert()

abort execution and revert state changes

revert(string memory reason)

abort execution and revert state changes, providing an explanatory string

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The following example shows how to use an error string together with revert and the equivalent require:

Copy // SPDX-License-Identifier: GPL-3.0 pragma soliditypp ^0.8.0; contract VendingMachine { function buy(uint amount) public payable { if (amount > msg.value) revert("Not enough Vite provided."); // Alternative way to do it: require( amount <= msg.value, "Not enough Vite provided." ); // Perform the purchase. } }

If you provide the reason string directly, then the two syntax options are equivalent, it is the developer's preference which one to use.

For more examples please refer to https://docs.soliditylang.org/en/v0.8.1/control-structures.html?highlight=panic#error-handling-assert-require-revert-and-exceptions (opens new window)