How to return the index value of transaction?

Question

I wish to return the new index value once the transaction is done.

pragma solidity ^0.4.18;
contract Courses {

    struct Instructor {
        uint age;
        string fName;
        string lName;
    }

    mapping (address => Instructor) instructors;
    address[] public instructorAccts;

    function setInstructor(address _address, uint _age, string _fName, string _lName) public {
        var instructor = instructors[_address];

        instructor.age = _age;
        instructor.fName = _fName;
        instructor.lName = _lName;

        instructorAccts.push(_address) -1;
    }

    function getInstructors() view public returns(address[]) {
        return instructorAccts;
    }

    function getInstructor(address _address) view public returns (uint, string, string) {
        return (instructors[_address].age, instructors[_address].fName, instructors[_address].lName);
    }

    function countInstructors() view public returns (uint) {
        return instructorAccts.length;
    }
}

So in the setInstructor I wish to return the index value like 0,1,2 (Whatever the index value will be there of public key index).

Can anyone help me with this?

score 1 · Answer 1 · answered Sep 09 '18 at 13:12

1

function setInstructor(address _address, uint _age, string _fName, string _lName) public returns(uint256){
    var instructor = instructors[_address];

    instructor.age = _age;
    instructor.fName = _fName;
    instructor.lName = _lName;

    return instructorAccts.push(_address) -1;
}

Hope this helps

answered Sep 09 '18 at 13:12

Jaime

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Thanks for your answer. But this do not work when we compile on injected web on remix . It will only work on VM. How can I make it work on injected web 3 or on live environment. – shrey bhardwaj Sep 09 '18 at 13:34
what do you mean it doesn't work, what error you got? – Jaime Sep 10 '18 at 09:30
It should work Shrey – Soham Lawar Sep 10 '18 at 13:21
Let me try again. – shrey bhardwaj Sep 14 '18 at 11:36

score 1 · Answer 2 · edited Apr 21 '19 at 20:18

geth is returning transaction hash and remix is returning index. This is a fundamental difference in behavior of geth and remix. The return value of a setInstructor.sendTransaction method is always the hash of the transaction that’s created. Transactions don’t return a contract value to the front end because transactions are not immediately mined and included in the blockchain. To get values from a function you should use solidity events.

Refer to this blog for understanding more about solidity events.

Refer this question to understand why to write return statements in solidity functions.

How to return the index value of transaction?

2 Answers2