Can you input a variable into a contract call?

Question

In ETH could you call a contract by inputting a variable parameter? As in the value of that parameter is unknown at call and must be evaluated at run-time?

Something like "someFunction( current_time_at_run_time );" - is this allowed?

Thanks.

Answer 1

You can't make the EVM interpolate things in the parameters you supply in your transactions. The code creating your transaction, typically JavaScript, can of course do whatever computations it likes to create the parameters, but in your case the time the transaction is created won't match the time it's executed (mined).

What you can do is wrap the call in another contract, and have the outer contract do the interpolation you want.

contract Inner {
  function someFunction(uint timestamp) {
    // do something with that timestamp
  }
}

contract Outer {
   function callInnerWithCurrentTime(address inner) {
     Inner(inner).someFunction(now);
   }
}