Day 19 - Function Modifiers

envoy1084 / 30-Days-of-Solidity

30 Days of Solidity step-by-step guide to learn Smart Contract Development.

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Contents

• Day 1 - Licenses and Pragma
• Day 2 - Comments
• Day 3 - Initializing Basic Contract
• Day 4 - Variables and Scopes
• Day 5 - Operators
• Day 6 - Types
• Day 7 - Functions
• Day 8 - Loops
• Day 9 - Decision Making
• Day 10 - Arrays
• Day 11 - Array Operations
• Day 12 - Enums
• Day 13 - Structs
• Day 14 - Mappings
• Day 15 - Units
• Day 16 - Require Statement
• Day 17 - Assert Statement
• Day 18 - Revert Statement
• Day 19 - Function Modifiers
• Day 20…

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This is Day 19 of 30 in Solidity Series
Today I Learned About Function Modifiers in Solidity.

Modifiers assist in the execution of a function’s behavior. The behavior of a function can be changed using a function modifier, they can also be called before or after a function is executed.

Solidity function modifiers help in the following:

• To access restrictions
• Input accuracy checks
• Hacks protection

Example:

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

The function body is inserted where the special symbol "_;" appears in the definition of a modifier. So if condition of modifier is satisfied while calling this function, the function is executed and otherwise, an exception is thrown.

Example:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

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

    function _mint(address to , uint tokenId) onlyOwner {
      mint(to, tokenId);
    }
}