title: Swift: Get all key value pairs from a String
body: <p>I have a <code>String</code> which has many key value pairs appended by a <code>&amp;</code> sign. i.e: <code>params = key1=Hello&amp;key2=Hello World&amp;key3=Hi Hello</code></p>
  
  <p>Is there a way to extract the values just by passing the keys present in the string? For example I want to extract the value of key1, key2, key3.</p>