A little doubt

[itsabinashb]

function callStoreFunction(uint256 _indexNumber, uint256 _simpleStorageNumber) public {
        SimpleStorage simpleStorage = simpleStorageArray[_indexNumber];   
        simpleStorage.store(_simpleStorageNumber);
    }

In line 1 we are passing a parameter _indexNumber, how we are knowing that it will store the index number??

[alymurtazamemon]

@imhacek I think you are asking that we are not adding any condition here to check whether at this index contract exists or not. Am I correct?

[krakxn]

how we are knowing that it will store the index number??

Because the user, when seeking to use the functionality this function provides, will aptly provide the correct parameter. I.e. they will use the index in the first parameter here: callStoreFunction(uint256 _indexNumber, uint256 _simpleStorageNumber)

An example to illustrate how this works:

(Written in pseudo-code for illustration, ignore syntactical errors)

library useFunction { 
    function sum(uint256 numberOne, uint256 numberTwo) returns(uint256){
        memory uint256 total = 0;
        total = numberOne + numberTwo;
        return total
    }

contract useLibrary {
   // ignoring formalization of numbers...
   using useFunction for uint256;
   uint256 contractNumberOne = 4;
   uint256 contractNumberTwo = 9;
   function demonstrateConcept () returns(uint256) {
       uint256 contractTotal;
       contractTotal = sum(contractNumberOne, contractNumberTwo)
       return contractTotal // returns sum, i.e. 13
       }
   }
}

[itsabinashb]

@alymurtazamemon So what are other ways to get user's input? I am on lesson 4 and as far as i remember all input i used as an user it was generated from function parameter.

[krakxn]

@itsabinashb

See the example pseudo-code I posted above, that should clarify it.

We create a function which receives a parameter which we assume will be passed onto it by users looking to use its functionality.

This is fundamental to functions; they serve some functionality assuming the parameters are given, then with the parameters the functionality can be used.

I am assuming you are a beginner, I would highly recommend mastering an OOP language before proceeding (for the ease in comprehension); elsewise, though possible, it will be really hard to understand what is happening.

[itsabinashb]

@krakxn I am not new in code, i know C, JS and little bit python, i am just trying to make my understanding crystal clear on solidity.

[krakxn]

Well, if you do then that is great. Because it works the same way (as described above) like the languages you know.

[itsabinashb]

@alymurtazamemon @krakxn Thanks both of you, never seen such active help desk, wish i will contribute in it soon.