如何根据索引数组更改元素的状态？

Question

So I have this state:

  state = {
    index: 0,
    routes: [
      { key: 'first', title: 'Drop-Off', selected: true },
      { key: 'second', title: 'Pick up', selected: false },
    ],
  };

I need to show and hide an element depending on the selected key, if it's true show it, false hide it.

   const { routes } = this.state;
   {routes[i].selected && (
      <View
        style={{
          flex: 1,
          justifyContent: 'center',
          alignItems: 'center',
        }}
      >
        ...
      </View>
    )}

So I need to do something like (pseudo code):

this.setState({ routes: routes[old index].selected = false, routes: routes[new index].selected = true })

What could be the best approach?

Answer 1

The pure immutable best practice way would be:

 this.setState(({ routes }) => ({ 
  routes: routes.map((route, index) => ({ ...route, selected: index === toSelect })),
}));

Answer 2

You could use the map() and a turnary operator so that if your array is empty, it will show an alternate code.

// in your Class
routeChecker = (route) => {
    if (route.selected === true) {
       return (
       <div>
            {/* display the things */}
        </div>
        )
    }
}
// in your return statement inside the render()
 {/* maps the `routes` from state.routes array if the array has elements, /*}
 {/* otherwise, shows an alternate code */}
<div>
 {this.state.routes.length ?
    (<div>
        {this.state.routes.map(route => (this.routeChecker(route)))}
    </div>)
    :
    (<div>
        {/* alternate code if array is empty */}
    </div>)
}
</div>