How to animate conditionally-rendered components?

Question

I'm trying to use React Motion UI Pack to animate the slide-in/slide-out animation for my Side Navigation. This is it:

constructor(props){
  super(props);
  this.state = {
    isThere: false,
    showOverlay: false
  } 
  this.updatePredicate = this.updatePredicate.bind(this);
  this.handleToggleClick = this.handleToggleClick.bind(this);
  this.handleOverlayClick = this.handleOverlayClick.bind(this);
}

componentDidMount() {
  this.updatePredicate();
  window.addEventListener("resize", this.updatePredicate);
}

componentWillUnmount() {
  window.removeEventListener("resize", this.updatePredicate);
}

updatePredicate() {
  this.setState({ isThere: window.innerWidth > this.props.breakWidth })
}

handleToggleClick(){
  this.setState({
    isThere: true,
    showOverlay: true
  })
}

handleOverlayClick(){
  this.setState({
    isThere: false,
    showOverlay: false
  });
}

let sidenav = (
  <Tag {...attributes} className={classes} key="sidenav">
    <ul className="custom-scrollbar">
      {src &&
        <li>
          <div className="logo-wrapper">
            <a href={href}>
              <img src={src} className="img-fluid"/>
            </a>
          </div>
        </li>
      }
      {children}
    </ul>
  </Tag>
);

return (
  <div>
    { isThere ? (
      <Transition
      component={false}
      appear={{ opacity: 0.2, translateX: -300 }}
      enter={{ opacity: 1, translateX: 0 }}
      leave={{ opacity: 0.2, translateX: -300 }}
    >
        { sidenav }
      </Transition>
      ) : (
        <Button color="primary" onClick={this.handleToggleClick} key="sideNavToggles">ClickMe</Button>
      ) }
    {showOverlay && (
      <div id="sidenav-overlay" onClick={this.handleOverlayClick} key="overlay"></div>
    )}
  </div>
    );
  }
}

The utility seems awesome, yet there is something I cannot wrap my head around. My component renders button or the sidenav depending on the breakWith prop. Clicking on the rendered button causes the SideNav to slide-in anyway, this time together with an overlay. Transition allowed for a smooth slide-in animation, but now I would like to apply a slide-out one upon clicking on the overlay.

Few hours passed and I'm starting to think it is impossible. Rendering of components is conditional & state-based (the isThere ? (... part in render()), right? As the pack offers no willLeave props, there seems to be no time to animate the leave in between the change of state and the re-render with the conditionally-rendered element already missing.

Or am I missing something?

Answer 1

yes - the answer found here effectively addresses the problem. To solve it, I moved the conditional logic of the component up, created appropriate variable, and encapsulated it inside a <Transition> in render(). If there is a lesson to be learned here, it is that <Transition> from Reakt Motion UI Pack (and, perhaps, elsewhere) does not fire its leave animation if surrounded by a conditional statement, making it impossible to use it together with ternary operator if you don't want the false component to be animated as well.