title: Getting the parameter types from an interface in TypeScript
body: <p>Given an interface like this:</p>
  
  <pre><code>interface IDelegates {
    delegateOne: (name: string, age: number) =&gt; string;
    delegateTwo: (date: Date) =&gt; number;
  }
  </code></pre>
  
  <p>How to define a method that takes in a func of the correct delegate type, based on the interface property name?</p>
  
  <p>I can get a type with just the property I want using <code>Pick&lt;IDelegates, 'delegateOne'&gt;</code> which returns a type: </p>
  
  <pre><code>{
    delegateOne: (name: string, age: number) =&gt; string;
  }
  </code></pre>
  
  <p>But I can't then figure out if there is a way to do <code>Parameters&lt;Pick&lt;IDelegates, 'delegateOne'&gt;&gt;</code></p>
  
  <p>I get why this doesn't work, but thinging there might be a way?  Basically I'd need <code>PickOne</code> or something, to return <em>just</em> the property 'delegateOne', rather than a type <em>containing</em> the property.</p>