Lesson 2: General formatting question.

[PeggCity]

Hello!

I'm working my was through the solidity course with very limited knowledge of coding.
I was hoping someone could clear up the formatting of the function for me and shed light on what it is I cannot grasp about the formatting.

Line 17 pushed the simpleStorage variable into the array. Got it!
Line 16 creates a new contract using the SimpleStorage.sol import then assigns it to a variable named simpleStorage but why does SimpleStorage need to be written before hand. Why can't you just write simpleStorage = new SimpleStorage()?

Also is there any reason why line 17 shouldn't just be written as:
simpleStorageArray.push(new SimpleStorage();
doing away with line 16 all together.

Hope someone can clarify the first question mainly about the context of that first SimpleStorage entry.

[JamesMckenna]

When I went through that lesson, I never tried writing it simpleStorageArray.push(new SimpleStorage()); and leaving out line 16. Maybe I should have tried before attempting to give the below explanation. Did you try it? Did the compiler allow it? I assume it threw an error.

I am not sure of your programming background and knowledge, so my answer maybe overly verbose....

Solidity is what's know as a strongly typed programming language. That means that we have to tell the Solidity compiler what type of data it is working with. Types in Solidity include uint16, uint64, uint256, string, array, struct, mapping......

line 4 in your screen shot import "./SimpleStorage.sol" imports a type. In this case, it of type Contract. At this point, SimpleStorage is just a concept, an abstraction, an idea per say; not a real object.

line 9 SimpleStorage[] public simpleStorageArray declares to the Solidity compiler that, for the contract type, StorageFactory, we want one of its members (in this case, a variable) to be of type Array, (a collection of something). That the collection is going to be made up of SimpleStorageobjects, and we want to name that collection, simpleStorageArray.

Line 16 SimpleStorage simpleStorage = new SimpleStorage(); we tell the compiler that the StorageFactory member (the function declaration on line 15), createSimpleStorageContract is to create a new SimpleStorage object and name that object simpleStorage.

So we need to tell the compiler that we have this idea of a SimpleStorage, but we want to make a real object from that idea new SimpleStorage.

Line 16 dissected:
SimpleStorage the data type (shape) so the compiler knows how to work with that data-object
simpleStorage the name or identifier, how we and the compiler should refer to that data-object
new SimpleStorage() we want to turn an idea or abstract into a real object, and it's going to take the 'shape' of the abstract data type, SimpleStorage.

simpleStorage is the name of the concrete object created from the abstract concept of SimpleStorage

Also is there any reason why line 17 shouldn't just be written as:
simpleStorageArray.push(new SimpleStorage();
doing away with line 16 all together.

Without new SimpleStorage(), the compiler say, I know of an abstract idea SimpleStorage, but I don't have any SimpleStorage objects to 'push' into the collection we named simpleStorageArray. It also tells the compiler that that object we want to 'push' into the collection is going to be the correct 'shape' to fit.

simpleStorageArray.push(new SimpleStorage(); would work in programming languages that support type inference; to my understanding, Solidity doesn't. Think round hole, square peg. In languages that support type inference, the compiler cares less about the 'shape' of the object, it tries to work with it regardless.

let me know if that explains why we need line 16.

[PeggCity]

Wow!! Thank you so much!

That explanation was perfect. The details are much appreciated!
Buttt! I will say simpleStorageArray.push(new SimpleStorage()); did in fact work for me! Not sure why of course. But it compiled and was feeding me the proper information.

Btw how do you highlight your snippets of code in light grey to make it more readable?

[JamesMckenna]

Buttt! I will say simpleStorageArray.push(new SimpleStorage()); did in fact work for me! Not sure why of course.

Good to know - something I need to keep in mind as I gain more experience with Solidity. As for why it worked, well I presume that Solidity doesn't really need the 'name' as long as it gets a instantiated object; not an abstract idea, and the new SimpleStorage() creates that object.

I did the highlighting by selecting the code I wanted to highlight, then click the <> button on top of the text input box

[PeggCity]

Cool!

Thanks again for going out of your way to give me some help! Hopefully I can do the same some time in the future :)

[JamesMckenna]

Hopefully I can do the same some time in the future :)

I'm sure you can and will.

[mistycyrus]

Hello! I am getting an error in the code below while compiling:

pragma solidity ^0.8.8;

contract SimpleStorage {
bool has FavoriteNumber = true;
uint favoriteNumber = 123; //defailt uint256
int favoriteNumber = 7777; //default int256
string favoriteNumberInText = "Seven";
address myAddress = 0x************************************;
bytes favoriteBytes = "Apple";
}

While compiling this code I am getting this error:
ParserError: Expected ':' but got identifier
-->

Please tell the solution.

[alymurtazamemon]

@mistycyrus This is a general question formating thread, you should create another discussion with type QA and leave you question there so we can discuss further.

[PeggCity]

How do I change this discussion to SOLVED??

[alymurtazamemon]

@PeggCity If you want to make it a QA then change the category above the top-right and then you will be able to select an answer.