title: How Would I Write A Function Requiring Sender to Hold an ERC20 to Use Function
body: <p>Does anyone know how to create a function that requires sender to have at least one token to use the function? For example, to require sender's balance to have an ether, I'd use:</p>
  <pre><code>require(balances[msg.sender] &gt;= 1 ether);
  </code></pre>
  <p>How would I instead create a requirement on msg.senders ERC20 balance of a particular token that was created through the contract they're interacting with? Thanks.</p>