diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/frequently-asked-questions.rst | 38 | ||||
| -rw-r--r-- | docs/types.rst | 5 |
2 files changed, 5 insertions, 38 deletions
diff --git a/docs/frequently-asked-questions.rst b/docs/frequently-asked-questions.rst index b6e5fe78..9cc08822 100644 --- a/docs/frequently-asked-questions.rst +++ b/docs/frequently-asked-questions.rst @@ -143,44 +143,6 @@ arguments for you. See `ping.sol <https://github.com/fivedogit/solidity-baby-steps/blob/master/contracts/45_ping.sol>`_ and `pong.sol <https://github.com/fivedogit/solidity-baby-steps/blob/master/contracts/45_pong.sol>`_. -When returning a value of say ``uint`` type, is it possible to return an ``undefined`` or "null"-like value? -============================================================================================================ - -This is not possible, because all types use up the full value range. - -You have the option to ``throw`` on error, which will also revert the whole -transaction, which might be a good idea if you ran into an unexpected -situation. - -If you do not want to throw, you can return a pair:: - - pragma solidity >0.4.23 <0.6.0; - - contract C { - uint[] counters; - - function getCounter(uint index) - public - view - returns (uint counter, bool error) { - if (index >= counters.length) - return (0, true); - else - return (counters[index], false); - } - - function checkCounter(uint index) public view { - (uint counter, bool error) = getCounter(index); - if (error) { - // Handle the error - } else { - // Do something with counter. - require(counter > 7, "Invalid counter value"); - } - } - } - - Are comments included with deployed contracts and do they increase deployment gas? ================================================================================== diff --git a/docs/types.rst b/docs/types.rst index 5a578072..69c846a6 100644 --- a/docs/types.rst +++ b/docs/types.rst @@ -13,6 +13,11 @@ Solidity provides several elementary types which can be combined to form complex In addition, types can interact with each other in expressions containing operators. For a quick reference of the various operators, see :ref:`order`. +The concept of "undefined" or "null" values does not exist in Solidity, but newly +declared variables always have a :ref:`default value<default-value>` dependent +on its type. To handle any unexpected values, you should use the :ref:`revert function<assert-and-require>` to revert the whole transaction, or return a +tuple with a second `bool` value denoting success. + .. index:: ! value type, ! type;value Value Types |