CODEWITHSUNDEEP
javascriptreactjsreact-native
Anish K.
Anish K.

Reputation: 2532

React: Mapping children of a parent component

So I want to add certain styles to any child that's appended to a component. Let's say the parent component is called Section and children are called Cardin this case. in Section.js I am trying this: -

renderChildren = () =>{
  return React.Children.map(this.props.children, (child, i)=>{
    let el = React.cloneElement(child,{
      style: {opacity:0.5}
    })
    return el
  })
}

render(){
  <ScrollView>
       {this.renderChildren()}
   </ScrollView>
}

The above approach doesn't work for me. And I would like to know why. Also is there a way where I could map across the children and wrap them in a new component? Something like this;

this.props.children.map(Child => <Wrapper> <Child/> </Wrapper> )

Upvotes: 45

Views: 117721

Answers (4)

Kim Skogsmo
Kim Skogsmo

Reputation: 479

Another variant for TypeScript which I think is clean:

const ChildrenWithProps = Children.map(children, child =>
    cloneElement(child as JSX.Element, props),
)

used like:

return (
  <div>
    {ChildrenWithProps}
  </div>
);

Of course, you need to know beforehand that what is passed as children definitely will be a valid child element, or you need to check it with isValidElement as previous answers suggested.

Upvotes: 3

Anja
Anja

Reputation: 519

And here the Typescript version when you write properties:

  const mapped = Children.map(children, (child, index) => {
    if(React.isValidElement(child)) {
      return React.cloneElement(child, {
        ...child.props,
        isFirst: index === 0,
        isLast: !Array.isArray(children) || index === children.length - 1,
      })
    }
    return null
  })

Upvotes: 15

Igor S
Igor S

Reputation: 969

I think this solution is the simplest for wrap every child. When the children are rendered, you receive an instance of the component, not the component function. And you just need to wrap the instance into the wrapper component as shown below.

this.props.children.map(child => <Wrapper>{child}</Wrapper> )

For TypeScript:

React.Children.map(props.children, child => {
  return <Wrapper>{child}</Wrapper>
})

Upvotes: 13

trixn
trixn

Reputation: 16344

To wrap your children into a wrapper just put the call to React.Children.map into the wrapper component:

const OpaqueWrapper = ({ children }) => (
    // check that children is defined 
    // if you do not want your wrapper to be rendered empty
    children && (
        <Wrapper>
            {React.Children.map(children, child => (
                React.cloneElement(child, {style: {...child.props.style, opacity: 0.5}})
            ))}
        </Wrapper>
    )
);

Also note that you have to merge the styles provided to the original child with the styles injected or you will lose the ability to style the children at all.

See this codesandbox for a working example.

As to why it did not work in your code: Are you sure that your <Card> component does handle the style prop correctly, i.e. applying it to it's children?

EDIT:

The sloution wraps all children components in a single wrapper, but I would like to wrap each child with the applied wrapper , as shown in my question.

The just move the wrapper into React.Children.map:

const OpaqueWrapper = ({ children }) => (        
    React.Children.map(children, child => (
       <Wrapper>
           {React.cloneElement(child, {style: {...child.props.style, opacity: 0.5}})}
       </Wrapper>
    )))
);

Upvotes: 73

Related Questions