April 2018
Intermediate to advanced
222 pages
5h 28m
English
Content preview from Solidity Programming Essentials
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The require statement
The word require denotes constraints. Declaring require statements means declaring prerequisites for running the function; in other words, it means declaring constraints that should be satisfied before executing the following lines of code.
The require statement takes in a single argument: a statement that evaluates to a true or false boolean value. If the evaluation of the statement is false, an exception is raised and execution is halted. The unused gas is returned to the caller and the state is reversed to the original. The require statement results in the revert opcode, which is responsible for reverting the state and returning unused gas.
The following code illustrates use of the require statement:
Let's take a ...
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