Using an imported variable inside function modifier

Question

I am trying to create a modifier that will cause a function to revert if a bool from an imported contract is = to true.

This is the modifier I am trying to make

 modifier notCompleted() { require( exampleExternalContract.completed = false ); _; }

This is the imported function and variable.

bool public completed; function complete() public payable { completed = true; }

Solidity gives me the error: Expression has to be an lvalue.

Iulian · Accepted Answer · 2022-06-02 21:35:28Z

First, your code should be

 exampleExternalContract.completed == false // notice the double equal

You should consider implementing a method and make it external

e.g

function whatIsComplete() external returns(bool) { return completed; }

and in your modifier have

require( exampleExternalContract.whatIsComplete() == false );

1 Answer 1