This Variable is not understandable.

[TimeKeyRoll]

Hi Guys! Need to understand this variable(red marked).
i understand how require works but not able to understand this Global variable and number 5 concept. what does that even mean? could anyone help me to understand this?
thanks in Advance.

[krakxn]

uint256 public number initialization explanation:

We declare a variable named number (or identifier), of type uint256 (or data type) which is public (or scope)

number = 5 declaration explanation:

To the variable we already defined above, we assign (by = operator) it a value of 5. So, number stores 5 now.

Hope this helped

[TimeKeyRoll]

Well still need to understand why in the first place we have had to declare it and what's the point of declaring it!? What benifits we get from it!? Does it have any usage of declaring number?

Sorry I'm just learning the basics. Thankyou

[krakxn]

So, as I have explained what they are essentially already, I will reply to the "point of declaring it" query now.

Simply, note the keywords too:

INITIALIZATION: uint256 public number is used to INITIALIZE the variable number, we store this in storage with a set size (256 bits) - the computer knows that we will use it sometime so it assigns space for it.

DECLARATION: number = 5 this is where we DECLARE that the variable number will hold the value 5, by assigning it with the = operator.

Now, when you are fluent with the fundamentals you can start using one-liners, or short-hand where you initialize and declare together. Maybe something like, uint256 public number = 5

Hope this answers your query

[Suhel-Kap]

This was done to explain the functionality of the **revert** feature of the fund() function's payable keyword.

A global variable number has been declared and its value is being altered in the fund() function. So, if you make a transaction of < 1eth the fund function sets the value of number = 5 (because it is placed above the require function) and then when it checks for the require statement it realises that the changes made up to this point have to be undone because the value does not satisfy being greater than 1eth.

So the bottom line is that the altered value is reverted back to its uninitialised state (0 in this case) because the require statement wasn't fulfilled.

Hope this clears things up :)

[TimeKeyRoll]

Brilliant explanation. I got that point. However question remains the same. If 'require' keyword is there to check the value of ether and also a message (not enough money) has been declared in case of reverting(rejection) . Then what's the logic and idea behind declaring the global variable 'number'. How this global veriable helping us!?
I understand if the value is as per requirement it will pass number 5 and if it's fails it will keep it to 0. But still don't understand why we using this if we are using 'require' keyword.

Sorry bro. It's getting lil messy. Lol

[Suhel-Kap]

I guess I get your point

Here is an attempt to satisfy your question

Let's suppose you are building a smart contract to get donations for some xyz cause, and you need the total number of donors. So you set totalDonors as a global variable and every time donate() function goes through correctly, you'll update the totalDonors by 1. (Let's assume donate() has a require function to take in a minimum amount of ETH).

I hope this example clears the image for you a bit.

[TimeKeyRoll]

Hey! as you have mentioned about lottery that's okay to understand and i have tried to impliment the same thing its working but as the original question its not clearing why did we mentioned global variable there. if we look at this donations example. we have declared the global variable because it has a usage and it can also count of the number of total donors whereas the original question(Global variable) does not eve have a usage. thats the question. lol hhaha

[Suhel-Kap]

Nah man that's really just for explanation's sake and nothing else. You don't need to declare the number variable in the global scope. It is meant for teaching purposes only.

[TimeKeyRoll]

Oh okay. Thank you for clearing doubts. :)