lesson-9 performUpkeep function

[TimeKeyRoll]

Does not understand how this line how it's written and working?
What's does this line mean? why would we write this line and what's its doing?

if (!upkeepNeeded) { revert lottery__UpKeepNotNeeded}

the entire code is mentioned below.

function performUpkeep(
        bytes calldata /*performData*/
    ) external override {
        (bool upkeepNeeded, ) = checkUpkeep("");
        // require(upkeepNeeded, "Upkeep not needed");
        if (!upkeepNeeded) {
            revert lottery__UpKeepNotNeeded(
                address(this).balance,
                s_players.length,
                uint256(s_raffleState)
            );
        }

[othaime-en]

Simple explanation: In this line, we are saying that if upkeepNeeded is not true, we are reverting function execution with lottery_UpkeepNotNeeded error.

Now a slightly detailed explanation, Solidity has this logical operator called Logical NOT written like ! This operator returns true if a condition is not satisfied and if it is satisfied, it returns false. So for example, lets say we have this condition 1>2 normally this returns false right? but if we use logical NOT ! in this expression it returns true. So !1>2 is TRUE and the opposite !2>1 is false.
So if somethis is true and you put ! in front it becomes false and if it is false and you put ! it becomes true.
Back to your question, when upkeepNeeded is true then !upkeepNeeded equates to false and the if statement doesn't execute. On the other hand, when upkeepNeeded is false, !upkeepNeeded becomes true meaning that the if statement executes and the line revert lottery__UpKeepNotNeeded() gets executed.

[othaime-en]

Hey In this case, we can simplify the expression assert(!upkeepNeeded) as assert.equal(upkeepNeeded, false) This is to mean that we want to assert that upkeepNeeded should be equal to false.
Using assert(!upkeepNeeded) is just a shorthand shortcut way of writing assert.equal(upkeepNeeded, false)

[TimeKeyRoll]

Cool! get it how it is written. But where does this false is coming? because we are above that is equal. nah?

[othaime-en]

In the line above, upkeepNeeded is initialized as const { upkeepNeeded } = await lottery.callStatic.checkUpkeep("0x") Since we use callStatic, the state doesn't change meaning that checkUpkeep returns false which is assigned to upkeepNeeded

[TimeKeyRoll]

Is 'callStatic' a function of J.s? What call static does it replicate the things which making an actual transaction but pass on it. Yeah?

[othaime-en]

callStatic comes with ethers and it allows us to simulate transactions going through but not actually changing the state of the blockchain.