What is a view function in Solidity?

In Solidity, a function that only reads but doesn’t alter the state variables defined in the contract is called a View Function.

If the statements below are found in a view function, the compiler will consider them as altering state variables and return a warning.

  1. Modify/over-write state variables.
  2. Create new contracts.
  3. Invoke a function that is not pure or view.
  4. Emit event.
  5. Using certain opcodes in inline assembly.
  6. Use selfdestruct.
  7. Use low-level function calls.
  8. Send Ether along with function calls.

Note: All the getter functions are view functions by default.

Syntax

function <function-name>() <access-modifier> view returns() {
  // function body
}

Code

In the code snippet below, we will see how to create a view function in Solidity.

pragma solidity ^0.5.0;
contract Example {
  // declare a state variable
  uint number1 = 10;
  // creating a view function
  // it returns sum of two numbers that are passed as parameter 
  // and the state variable number1
  function getSum(uint number2, uint number3) public view returns(uint) {
    uint sum = number1 + number2 + number3;
    return sum;
  }
}

Explanation

  • Line 3: In the above code, we create a contract named Example.

  • Line 5: We declare a static variable number1.

  • Line 10: We define a view function named getSum().

  • Line 11-12: This function accepts two parameters number2 and number3, calculates the sum of number1, number2, and number3, and returns the sum.

Since getSum() is a view function, we can read variable number1 but can’t modify it.

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