"Using" Keyword and Passing Object as Parameter?

[michaelinwords]

Hello, all! I'm at 4:28:11 in the 32-hour course (Learn Blockchain, Solidity, and Full Stack Web3 Development with JavaScript), where Patrick introduces the line using PriceConverter for uint256; as a way of attaching the PriceConverter library to uint256. This allows us to call the library's functions on any instance of uint256.

My question, however, is what's happening with how this "using" keyword is passing the object? My initial thought was that in practice it would look like:

uint256 my_number = 1;
my_number.someFunction(my_number);

In reality, the object/uint256 is passed as a parameter non-explicitly, a feature that seems to be from Solidity's using keyword, not some other general pattern inherited from JavaScript (as I initially imagined). No problems with this part.
But, then, I thought I would do as I've seen in other languages: in the library's functions, I would just have the first parameter be called "self" to make it unambiguous. This appears to work fine when a function is actually called in the FundMe.sol contract, but the PriceConverter library throws an error if a uint256 doesn't actually call the function somewhere in FundMe.sol. When no FundMe.sol uint256 calls the function, PriceConverter does not allow to defining a parameter for that passed object in the function (for example: function get_version(uint256 self) OR function get_price(uint256 self) -- I've seen in many other languages that even if the function doesn't actually use the passed object, it should be fine (not cause errors) to pass it in.

This set of behaviors seems really strange and difficult to predict to me, so I figure I'm missing a couple concepts, maybe from Solidity's particular way of doing things or perhaps larger, general programming structures. 🔍 What specific concepts do you all see at play here? Why can functions have that subtly-passed object parameter defined only when the function is actually called on an object/uint256? 🔍

This is my first posting here, so please be kind in pointing out mistakes/gaps in my understanding!

[krakxn]

Good read (to resolve the confusion w/ the using keyword--it, essentially, is just syntactic sugar): Link to the Article

[michaelinwords]

Thanks for responding! I actually read that article before posting haha (will reread it soon), but was hoping folks could provide more clarity, especially on which parts are Solidity and which parts are other advanced/rare coding concepts!

[krakxn]

It is so because "As we can see, by adding the keyword using we could give any uint within the SomeContract the libraries functions and pass the uint as the first parameter of that function." with emphasis on the latter; the parameter must be in accordance with the data-type in the using... statement, in this case uint--which is precisely why the error occurs.

If you insist on not using a constant data-type, using PriceConverter for * can be used here for versatility.

[alymurtazamemon]

@michaelinwords Really struggling to understand! Could you please elaborate with examples of what you were expecting and what it is?