Modifiers misunderstanding

Question

pragma solidity ^0.4.0;

contract test {

  bool test_bool1 = false;

  bool test_bool2 = true;

  modifier test_modifier(bool _test_bool){
      if (_test_bool == false) throw;
      _;
  }

  function test1(uint input1) test_modifier(test_bool1) returns (uint){
      return input1;
  }

   function test2(uint input2) test_modifier(test_bool2) returns (uint){
      return input2;
  }

}

Here is my simple modifier test code. If I deploy that contract and call test.test1(5), I expect shoud not return anything because test_bool1 is false. The result of eth.getTransaction() of this function call transactionHash will be:

>console.log((eth.getTransaction("0x9da931ab4a750423bd780a3b76b70d32ab14f7af0bb967f765c72f9e84674e48").input))
    0x19ae89940000000000000000000000000000000000000000000000000000000000000005
    5

And if I do it again with test.test2(5) (which passed modifier test) I get:

> console.log((eth.getTransaction("0xdf2d0d0ff2a7aed5bf53ca23ccbcb05c76f350255120a098829c839965c4439d").input))
0xcaf446830000000000000000000000000000000000000000000000000000000000000005
5

Why did that happend?
Is there anything about first 8 digits of transaction input? caf44683, 19ae8994

The first 4 bytes are the method signature (see this how it is produced https://ethereum.stackexchange.com/a/1171). Without the code you are using is hard to say exactly what is going on. But test.test1(5) should throw, check the gas used in the transaction receipt. And test.test2(5) should succeed, but remember you cannot check the return value if you call a contract method (https://ethereum.stackexchange.com/a/770). — Ismael, Jul 08 '17 at 15:41

Jakub Wojciechowski · Answer 1 · 2017-07-08T16:22:54.277

0

You get transaction details for a failed transaction but later on, you are checking the input value of this transaction, which indeed for the first transaction is 5 (data sent by you as specified in docs):

).input)

rather that checking for a result value. To do so, you may publish an event populated by a return value and listen for such an event.

edited Jul 08 '17 at 16:22

answered Jul 08 '17 at 16:08

Jakub Wojciechowski

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How do I check for a result value? – shegeley Jul 08 '17 at 16:12
I've edited my answer proposing the usual pattern with publishing an event. – Jakub Wojciechowski Jul 08 '17 at 16:23

Modifiers misunderstanding

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