solidity, set value to state Variables, the value not changed

Question

I'm trying to change the state variable value of solidity, and test on the geth console, but the value of state variable is not changed. The steps are as below：

1: Write a simple smart contract code by solidity as below

pragma solidity ^0.4.0;

contract SimpleStorage {

uint public storedData=99;
mapping(string => uint)  balances;



function set(uint x) public returns (uint){

    storedData = x;
    return storedData;

}

function get() public constant returns (uint) {

    return storedData;

}

function multiply(uint a) returns(uint d) {
    return a * 7;
}

function setmapping(string key,uint value) returns(uint v)
{
     balances[key] = value;
     return balances[key];
}

function getmapping(string key) returns(uint v)
{
    return balances[key];
}

function kill()
{ 

}


}

2: compile the code by the truffle, use command

truffle compile

3:start the geth, unlock account, and start the minner

4:deploy the smart contract

truffle migration --reset

and then I see the console output as below

Using network 'development'.
Running migration: 1_initial_migration.js
Replacing Migrations...
... 0x8ccf9e1599c2760ff3eed993be10929403e1faa05489a247a067f4f06536c74c
Migrations: 0xec08113a9e810e527d99a1aafa8376425c4a75ed
Saving successful migration to network...
... 0xedbf12715b736759e9d9297cbaaeb3151d95f478c2f1ee71bff4819d2dbb47e5
Saving artifacts...
Running migration: 2_deploy_contracts.js
Replacing SimpleStorage...
... 0xff5b00f9b14d8ecea4828c3ad8e9dbfa9d685bc0b81530fc346759d7998b060f
SimpleStorage: 0x96cf1e076f4d99a5d0823bd76c8de6a3a209d125
Saving successful migration to network...
... 0x3452a9e76b73e250de80874ebc3fd454724ebf6a15563bee0d5ba89b7b41909f
Saving artifacts...

which means the smart contract deployed to geth successfully

5: Then in the geth console, I set abi variable as below:

abi=[{"constant":true,"inputs":[],"name":"storedData","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"changeStorage","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"kill","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"getAll","outputs":[{"name":"","type":"uint256"},{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"x","type":"uint256"}],"name":"set","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"get","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"key","type":"string"},{"name":"value","type":"uint256"}],"name":"setmapping","outputs":[{"name":"v","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"refrenceType","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"changeMemory","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"key","type":"string"}],"name":"getmapping","outputs":[{"name":"v","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"a","type":"uint256"}],"name":"multiply","outputs":[{"name":"d","type":"uint256"}],"payable":false,"type":"function"}]

6: Get an contract instant as below:

test=eth.contract(abi).at("0x2f3970e8e4e2f5ed4ccb37b0f79fe5598700e2f0")

7: Run the set()

test.set.call(22);

The out put is 22, which I think the state variable storedData was successfully set to the new value 22, but when I run below code to read the storedData,

test4.get()

the return value is still 99, which mean the value of storedData was not changed, beside use the uint to do the testing, I also tried the mapping, but the answer is as same as uint, I don't know if I was wrong in somewhere or the state variable is not allowed to be modified, could anyone help me?

Thanks.

Answer 1

From the question, this is the call that is not changing state:

test.set.call(22)

In order to change state, you must issue a transaction. A call(...) only tells you what would happen if you were to send a transaction. For more background, see: What is the difference between a transaction and a call?

So you can replace the above line with:

test.set.sendTransaction(22)

Alternatively, web3.js will automatically attempt to decide whether to use a transaction or a call. So in this case you can use simply:

test.set(22)

For more background on how web3.js decides, see: How does web3.js decide to run a call() or sendTransaction() on a method call?