title: Component List don't update state after deleting one item
body: <p>I have an issue trying to update a list of stateful  components created with by mapping a list of strings. The issue is showing when i remove one of this components by slicing the array to remove an element by its index. </p>
  
  <p>Every component has his own state, that im fetching from an API. the problems is that when i remove an element of the array, the state of next component overlaps the one that i deleted Component.</p>
  
  <p>My code looks something similar to this:</p>
  
  <pre><code>class MyDashboard extends React.Component {
   constructor(props){
    super(props);
    this.state = {
      activeItems: [0,1,2,3],
    }
   this.removeItem = this.removeItem.bind(this);
  }
  
  removeItem(indx){
   let tempItems= this.state.activeItems;
   tempItems.splice(indx,1);
   this.setState({activeItems:tempItems});
  }
  
  render(){
      let conditionalDash;
      let conditionalComponent;
      let temporalArray = this.state.activeEntries.map((entry , i) =&gt; {
        return  (&lt;MyDash key={i} index {i}/&gt; removeItem={this.removeItem});
  });
  
  render(){
   return (
     &lt;div id='dashContainer'&gt;
      {temporalArray}
     &lt;/div&gt;
    )
   } 
  }
  </code></pre>
  
  <p>In my MyDashComponent i have a something like this:</p>
  
  <pre><code>class MyDash extends React.Component{
  constructor(props){
    super(props);
    this.state={
     fetchedData:null,
    }
   }
  componentDidMount(){
    API.fetchData(this.props.index).then(response =&gt; {
      this.setState({fetchData:response.data})
    )
  }
  render(){
   return(
    &lt;div&gt; {this.props.index} {this.state.fetchedData}&lt;/div&gt;
   )
  }
  }
  </code></pre>
  
  <p>Is there something that i'm missing? </p>
  
  <p>The behavior that i'm getting is that when the i remove the this.state.activeItems[2] the state of this element is the same as the previous component. I was expecting that the state of the element[2] will be the same state that has the element[3]. </p>
  
  <p>Edit:
  Something that i forget to tell,  is that the props of MyDash component are correct, is just the state that doesnt belong to the component, it is from the deleted component.</p>
  
  <p>Thanks for reading and i hope that somebody can help me with this.</p>