Invalid Address Error when interacting with a smart contract & Why it works with metacoin

Question

I solved the error accroding to Invalid Address solution

PriceContract.web3.eth.defaultAccount=PriceContract.web3.eth.coinbase

The contract I run was a very simple set-get variable which I adapted according to the truffle metacoin sample.

My question is: why metacoin runs ok and my contract needs to assign the defaultAccount?

In both cases I run the contract against a local geth node.

Answer 1

I found what was different between metacoin and my contract.

In metacoin when calling sendCoind a last parameter is added: {from: account}

Now my app runs without setting the defaultAccount.