I try to animate a div with reactjs using async data via redux and it's not clear to me when can I have a reference to the virtual dom on state loaded
.
In my case I have a div with id header
where I would like to push down the container when data was populated.
If I try in componentDidMount than I get Cannot read property 'style' of undefined
because componentDidMount still having a reference to an on load container
class HomePage extends React.Component {
constructor(props) {
super(props);
this.state = {
sliderLength: null
}
}
componentDidMount() {
this.props.actions.getSlides()
if(this.header) {
setTimeout(function() {
this.header.style.bottom = -(this.header.clientHeight - 40) + 'px';
}, 2000);
}
//header.style.bottom = -pushBottom+'px';
}
componentWillReceiveProps(nextProps) {
let {loaded} = nextProps
if(loaded === true ) {
this.animateHeader()
}
}
animateHeader() {
}
componentWillMount() {
const {slides} = this.props;
this.setState({
sliderLength: slides.length,
slides: slides
});
}
render() {
const {slides, post, loaded} = this.props;
if(loaded ===true ) {
let sliderTeaser = _.map(slides, function (slide) {
if(slide.status === 'publish') {
return <Link key={slide.id} to={'portfolio/' + slide.slug}><img key={slide.id} className="Img__Teaser" src={slide.featured_image_url.full} /></Link>
}
});
let about = _.map(post, function (data) {
return data.content.rendered;
})
return (
<div className="homePage">
<Slider columns={1} autoplay={true} post={post} slides={slides} />
<div id="header" ref={ (header) => this.header = header}>
<div className="title">Title</div>
<div className="text-content">
<div dangerouslySetInnerHTML={createMarkup(about)}/>
</div>
<div className="sliderTeaser">
{sliderTeaser}
</div>
<div className="columns">
<div className="column"></div>
<div className="column"></div>
<div className="column"></div>
</div>
</div>
<div id="bgHover"></div>
</div>
);
} else {
return <div>...Loading</div>
}
}
}
function mapStateToProps(state) {
return {
slides: state.slides,
post: state.post,
loaded: state.loaded
};
}
function mapDispatchToProps(dispatch) {
return {
actions: bindActionCreators(slidesActions, dispatch)
};
}
function createMarkup(markup) {
return {__html: markup};
}
export default connect(mapStateToProps, mapDispatchToProps)(HomePage);
How do I deal in this case with states?
Between I found a solution but not sure if is the right workaround
componentDidUpdate() {
if(this.header) {
setTimeout(function() {
this.header.style.bottom = -(this.header.clientHeight - 35) + 'px';
}, 2000);
}
}
In general, try to avoid using ref
as much as possible. This is particularly difficult if you're new to React but with some training, you'll find yourself not needing it.
The problem with modifying the styles like you're doing is that when the component will render again your changes will be overwritten.
I would create a new state
property, say state.isHeaderOpen
. In your render
method you will render the header differently depending on the value of this header e.g.:
render () {
const {isHeaderOpen} = this.state
return (
<header style={{bottom: isHeaderOpen ? 0 : 'calc(100% - 40px)'}}>
)
}
Here I'm using calc
with percentage values to get the full height of the header.
Next, in your componentDidMount
simply update the state:
componentDidMount () {
setTimeout(() => this.setState({isHeaderOpen: false}), 2000);
}
In this way, the component will render again but with the updated style.
Another way is to check if the data has been loaded instead of creating a new state
value. For example, say you're loading a list of users, in render
you would write const isHeaderOpen = this.state.users != null
.