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I have a contract which offers two functions:

1) A state modifying function which takes two parameters

2) A constant function

I have a web frontend in React calling these functions. When I call the constant function from the React frontend, everything works. But when I call the state modifying function from the frontend using web3, I get an invalid opcode error. However, the function does work when I call it from Truffle console, so the Solidity function itself is correct.

Here's how I'm calling from web3 1.0:

    contract.methods.createNewPlayer(
      '0x35000f8407c2358Fbb089C2aE4e70fE005f4F6cD',
      100
    ).send({ from: '0xc7edb363e01f7964f9fac9bf883afeee64fb2d93' })
     .then((receipt) => {
       console.log(receipt)
    })
    .catch((error) => {
      console.log(error);
    });

This results in an invalid opcode. And when I call from Truffle console like so:

    inst.createPlayer(
    '0x35000f8407c2358Fbb089C2aE4e70fE005f4F6cD',
    100, { from: '0xc7edb363e01f7964f9fac9bf883afeee64fb2d93'})

Everything works.

What reasons could there be for this? The contract is deployed on TestRPC.

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5
  • Is your solidity function mark as payable? – Chim Jan 16 '18 at 12:13
  • @Chim No, but it's not supposed to be as it doesn't receive any ether. – Bastien Jan 16 '18 at 12:29
  • If you change the state, then function should mark as payable. And this does not check in truffle / testrpc – Chim Jan 16 '18 at 12:31
  • @Chim, nope that's not it. When I try to send value from truffle like so: i.createNewPlayer('0x35000f8407c2358Fbb089C2aE4e70fE005f4F6cD', 100, { from: '0x3909591500d5037689c7794f501986de7f9e764c', value: 100 }); I get: Error: Cannot send value to non-payable function. So Truffle does check for it. – Bastien Jan 16 '18 at 13:06
  • Just mark the function as payable and try. Or share the function. – Chim Jan 16 '18 at 13:50
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Found the issue.

So I tried to call another state-modifying function from my frontend and that worked.

At this point, I know one state modifying function works from the frontend, and the other doesn't. While both work from truffle.

On a hunch, I added a gas: value to the one which wasn't working like so:

    contract.methods.createNewPlayer(
      '0x0728f10c5a118883ecfb113a7b43bc627849fb45',
      100
    ).send({
      from: '0xf3b22a49ad7f5ad0ffe9693e4a22121ed3738f73',
      gas: 3000000 
    })

And it worked. I had a faulty assumption that web3 was handling the required gas amount in the background but that's false. Also, there's no actual default gas value which web3 uses.

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