Q:

Change parent's state from a child and use it in another child react-native

I need to change parent component A's state from a child component B and use that updated state in another child component C of that parent component A . I did the following. I could update parent component from the child component but the second child component is still getting the old state of the parent component. So what's wrong here?
Component A has B,C childs. (here, A is also someone's child)
  class A extends Component {
        constructor(props) {
          super(props);
        });

        this.state = {
          name:this.props.name // first it gets name from A's parent
        }
        setName(UpdatedName){
          this.setState({ name: UpdatedName });    
        }
       render() {
          return (
            <View>
             <B callBackFromA={this.setName.bind(this)}/>
             <C name={this.state.name}/>
            </View>);
          }
       }

From A's child component B, I want to change A's state.name from a call back function. And it does (tested)  
 class B extends Component {
            constructor(props) {
              super(props);
              callBackFromA :this.props.callBackFromA
            });

            this.state = {                 
            }

         render() {
          return (
            <View>
             <TouchableOpacity onPress={()=>this.callBackFromA('new name')}> </TouchableOpacity>
            </View>);
          }
       }

    }

A's state.name is also passed as a prop to A's another child component C.
After I change A's state.name from B, then I need to save that from component C.   
  class C extends Component {
            constructor(props) {
              super(props);
            });

            this.state = {
              name:this.props.name
            }
            saveData(){
              //..problem is that this getting old state.name of A after B changes..
              console.log(this.state.name);   
            }
         render() {
          return (
            <View>
             <TouchableOpacity onPress={()=>this.saveData()}> </TouchableOpacity>
            </View>);
          }
       }

    }

A:

you need to use componentWillReceiveProps function in C class. Using this method you can update C class according to its updated props.
componentWillReceiveProps(nextProps)
{
   if(this.props.name != nextProps.name)
   {
    //do your task
     this.setState({name:nextProps.name})
   }
}

https://facebook.github.io/react/docs/component-specs.html

