SolidityTuts

Errors

error handling are moslty done to prevent the uneceesary use of gas. means refund of gas, any variable that is updated will be reverted

error handling done using require, assert, revert

require ==> it is mostly used to validate the user inputs and for access control who gets to call the function

require used where we get input from outside world, user or from other function.

in case of require when some error thrown then whatever gas cossumed will be gone but remaining will be given to user

revert ==> it is also does same thing as require but it is mostly used to prefer in nested condtions.

assert ==> it will be always used to check for conditions that should always be true. these are used only for internal checking

not used for user input. in case of error it will consume gas will not revert back to user so it should use only for internal checks

3 ways to send ether

transfer ==> ### use 2308 gas, if trasfer fail for some reason then whole function fails.

trasfer will be useful there when hacker try to call trasfer again and again then it will fail because it will cross 2300 gas. so it stops transfer

send ==> ### use 2300 gas, returns bool in case of successful trasaction or not.

call - ### all gas, returns bool and data. can use custom gas value

fallback and recieve inbuilt function

fallback ==> must have external visibility, and payable

fallback function always receives data, but in order to also receive Ether it must be marked payable.

If the version with parameters is used, input will contain the full data sent to the contract (equal to msg.data) and can return data in output

receive ==> must have external visibility, and payable

but in order to also receive Ether it must be marked payable