title: setState on only one variable
body: <p>I have a react native app with the state:</p>
  
  <pre><code>this.state={
          nameOne:"team 1",
          nameTwo:"team 2",
          pointsForEvents:{
              lap: 1,
              homeRun: 5,
              lyre: 3,
              oneHandCatch: 5,
              burned: 1,
              burnOut: 10,
          }
      }
  </code></pre>
  
  <p>Then I want to update the variables in pointsForEvents:</p>
  
  <pre><code>&lt;TextInput
          keyboardType="number-pad"
          onChangeText={(lyre) =&gt;{lyre = parseInt(lyre); this.setState({pointsForEvents:{lyre}})}}
          value={this.state.pointsForEvents.lyre+""}
      /&gt;
  </code></pre>
  
  <p>But the setState updates the other variables within "pointsForEvents" as well and since a value is not specified, they are set to undefined. How do I update only this one value.</p>
  
  <p>PS: what is the correct vocabulary for a variable within an object (like components are parents to their child components).</p>