Where to use function modifiers

Function modifiers are simple snippets that can change the behavior of a contract. In this recipe, you will learn how to create and use function modifiers in solidity.

How to do it...

1. Modifiers are declared with the modifier keyword as follows:

modifier modifierName {
    // modifier definition
}

2. The function body is inserted where the _ symbol appears in the definition of a modifier:

modifier onlyOwner {
    require(msg.sender == owner);
    _;
}

3. Modifiers can accept parameters like functions do. The following example creates a generic modifier to verify the caller address:

contract Test {
    
    address owner;
    
    constructor() public {
        owner = msg.sender;
    }
    
    modifier onlyBy...