What is "bytes memory"?

[yyc13236]

I've seen "bytes memory" used as argument at different places in Lesson-9.
But can't quite understand what it means.
For example:

  function checkUpkeep(bytes memory)
    public
    view
    override
    returns (bool upkeepNeeded, bytes memory)
  {
    bool isOpen = RaffleState.OPEN == s_raffleState;
    bool timePassed = ((block.timestamp - s_lastTimeStamp) > i_interval);
    bool hasBalance = address(this).balance > 0;
    bool hasPlayers = s_players.length > 0;
    upkeepNeeded = (timePassed && isOpen && hasBalance && hasPlayers);
    return (upkeepNeeded, '0x0');
  }

Can anyone explain?
Thank you!

[krakxn]

 function checkUpkeep(bytes memory)

Here, the function checkUpkeep()is a parameterized function (a function which requires parameters). In addition, (bytes memory) basically is a variable (any arbitrary name can be used, in this case memory) of the data-type bytes.

The word "memory" likely threw you off. It is just a name. You can do bytes yangyueche as well; it is the data-type which is compulsory.

---

Now, as to the how:

The function above has the keyword override; therefore, this implies that the function in the inherited contract has a parameter of the bytes type. This is why we have the bytes variable in the first place. Of course, in our case, we did not really use that variable, which is why it was commented out.

[yyc13236]

Thank you so much.
YES! I was actually confused by "memory", I thought "bytes memory" is a kind of type in solidity.
Thanks!

[RamanSB]

Yeah I wonder why they would have used the 'memory' as a variable name when memory refers to a Data location in Solidity. Surely the solidity team should introduce keywords that are reserved.

In Java I wouldn't be able to use a keyword like volatile or synchronized as a variable name or method parameter as it is reserved.