Modifiers

Modifiers are another concept unique to Solidity. Modifiers help in modifying the behavior of a function. Let's try to understand this with the help of an example. The following code  does not use modifiers; in this contract, two state variables, two functions, and a constructor are defined. One of the state variables stores the address of the account deploying the contract. Within the constructor, the global variable msg.sender is used to input the account value in the owner state variable. The two functions check whether the caller is the same as the account that deployed the contract; if it is, the function code is executed, otherwise it ignores the rest of the code. While this code works as is, it can be made better both in terms of readability and manageability. This is where modifiers can help. In this example, the checks are made using the if conditional statements. Later, in the next chapter, we will see how to use new Solidity constructs, such as require and assert, to...