title: How do I add a position strategy to an Angular CDK overlay?
body: <p>How do I add a positioning strategy (<code>ConnectedPositionStrategy</code>) to an Angular CDK overlay?</p>
  
  <p>I've tried specifying it via the <code>positionStrategy</code> property and passed it into <code>overlay.create()</code>.</p>
  
  <pre class="lang-ts prettyprint-override"><code>import { Overlay, ConnectedPositionStrategy } from '@angular/cdk/overlay';
  // ...
  export class MyComponent {
      constructor(private overlay: Overlay){}
      showOverlay() {
          let overlay = this.overlay.create({positionStrategy: ConnectedPositionStrategy});
          // ...
      }
  }
  </code></pre>
  
  <p>But I get this error:</p>
  
  <pre><code>ERROR in src/app/explore/explore.component.ts(48,40): error TS2345: Argument of type '{ positionStrategy: typeof ConnectedPositionStrategy; }' is not assignable to parameter of type 'OverlayConfig'.
    Types of property 'positionStrategy' are incompatible.
      Type 'typeof ConnectedPositionStrategy' is not assignable to type 'PositionStrategy'.
        Property 'attach' is missing in type 'typeof ConnectedPositionStrategy'.
  </code></pre>
  
  <p>Am I missing something? The docs aren't very clear about <strong>how</strong> to specify a positioning strategy.</p>
  
  <p>Here are my dependencies (outputted from <code>ng version</code>):</p>
  
  <pre><code>    _                      _                 ____ _     ___
     / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
    / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
   / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
  /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                 |___/
  
  Angular CLI: 1.6.1
  Node: 8.9.0
  OS: darwin x64
  Angular: 5.1.1
  ... animations, common, compiler, compiler-cli, core, forms
  ... platform-browser, platform-browser-dynamic, platform-server
  ... router, service-worker
  
  @angular/cdk: 5.0.1-2436acd
  @angular/cli: 1.6.1
  @angular/flex-layout: 2.0.0-beta.12-82ae74c
  @angular/material: 5.0.1-2436acd
  @angular-devkit/build-optimizer: 0.0.36
  @angular-devkit/core: 0.0.22
  @angular-devkit/schematics: 0.0.42
  @ngtools/json-schema: 1.1.0
  @ngtools/webpack: 1.9.1
  @schematics/angular: 0.1.11
  @schematics/schematics: 0.0.11
  typescript: 2.4.2
  webpack: 3.10.0
  </code></pre>
  
  <p>Additionally, I've tried initializing a <code>positionStrategy</code> via the <code>new</code> keyword, but now I've no idea what to pass the arguments as.</p>