recursive data

[Gregoor]

First off all, love idea and the great talks about it on ReactEurope. But I still get stuck quite a lot (which I should expect from a technical preview). Here is my current problem:

My data is modeled like this:

type Babushka {
  id: !String,
  name: !String,
  babushkas: [Babushka]
}

Now I want to display a Babushka list for which I have a List and a ListItem Component:

list.js

class BabushkaList extends Component {

  render() {
    return <ul>{this.props.babushka.babushkas.map(b => <BabushkaListItem babushka={b}/>)}</ul>;
  }

}

export default Relay.createContainer(BabushkaList, {

  fragments: {
    babushka: () =>  Relay.QL`
      fragment on Babushka {
        babushka {
          ${BabushkaListItem.getFragment('babushka')}
        }
      }
    `
  }

});

list-item.js

class BabushkaListItem extends Component {


  render() {
    return (
      <li onClick={this.onClick.bind(this)}>
        {this.props.babushka.name}
        <ul><BabushkatList babushka={this.props.babushka}</ul>
      </li>
    );
  }

}

export default Relay.createContainer(BabushkaListItem, {

  fragments: {
    babushka: () =>  Relay.QL`
      fragment on Babushka{
        name,
        ${BabushkaList.getFragment('babushka')}
      }
    `
  }

});

Naturally this leads to the stack size being exceeded. Am I doing something wrong fragment wise?

[josephsavona]

Recursive fragments are supported so long as you explicitly specify a stopping point. The pattern for this is to create a variable that determines if the nested item should be expanded or not - default it to false, and then only "expand" the items one level deep to begin with:

export default Relay.createContainer(BabushkaListItem, {
  initialVariables: {
    expand: false, // use `this.props.relay.setVariables({expand: true})` to expand an additional level
  },
  fragments: {
    babushka: (variables) =>  Relay.QL`  # note the `variables` argument here
      fragment on Babushka{
        name,
        ${BabushkaList.getFragment('babushka').if(variables.expand)} # getFragment().if(variables.foo)
      }
    `
  }
});

The parent component of this list can then specify that the first level of items should be expanded initially:

Relay.createContainer(Foo, {
  fragments: {
    foo: () => Relay.QL`
      fragment on Foo {
        ${BabushkaList.getFragment('babushka', {expand: true})} #override the default value to expand a single level of the list
      ...

[Gregoor]

Just what I was looking for! Thanks a lot Joesph.

[Gregoor]

Now I'm getting the following error:

Warning: RelayContainer: Expected prop `babushka` supplied to `BabushkaList` to be data fetched
by Relay. This is likely an error unless you are purposely passing in mock data that conforms to
the shape of this component's fragment.

Which doesn't make a whole lot of sense to me, because the babushka being passed to the List component is obviously fetched by Relay and not mocked by me. Am I missing something?

[josephsavona]

@Gregoor is it possible to link to a gist of the code for the parent and child component?

[Gregoor]

Does this suffice?

I can't really make sense of the error in that context. :( Thanks for getting back to me so quickly

[josephsavona]

Commented on the gist, but since SpeciesList expects the species prop to be an array of species, it should mark the fragment as plural: fragment on Species @relay(plural:true) {...}.

[Gregoor]

Out of all the words in the english language, I pick one where the singular and plural is isomorphic. Oh brain, why?

Anyway thanks, didn't know about the annotations(?). Are they already documented somewhere?
But I do think that species is singular in both cases, since the list component fetches the subspecies itself (which should be available).

I changed the naming once again to something more familiar and heteromorphic.

[Gregoor]

http://stackoverflow.com/questions/32497759/recursive-data-components-later-fetches-throwing-an-error

[grifx]

Hi @Gregoor @josephsavona ...,
I'm a little bit confused. React, Relay and GraphQL are quite new for me.
Is it possible for example to render recursively a directory structure with n descendants in a single http request?
If not, what's the source of the "problem"?

• GraphQL doesn't provide a syntax to query recursively data
• or Relay doesn't know how to use this GraphQL syntax.

Relay batch the queries so in the worst case scenario, if I understand, I'll have a single GraphQL Query per level and by using a condition like ${BabushkaList.getFragment('babushka') we can tweak the thing to get n levels at the same time.

Thanks for clarifications.

[kassens]

@grifx: Instead of a boolean you can use a number that you decrement every level of recursion. If it's <= 0 you don't expand.

[dminkovsky]

What is the deal with #if() in BabushkaList.getFragment('babushka').if(variables.expand)? It looks like RelayContainer.getFragment() returns a RelayQueryFragment which doesn't seem to have an #if() on its prototype.

** Edit **

Posted too soon: it's a RelayFragmentReference. Will continue investigating but any guidance regarding where I might read (non-code) about this would be great.

[josephsavona]

@dminkovsky RelayFragmentReference and the if/unless functions on it aren't documented. The plan is to replace these with standard GraphQL @include/@skip directives so that you could write something like:

fragment on Foo {
  ${Child.getFragment('foo')} @include(if: $var) @relay(variables: {foo: $bar})
}

[dminkovsky]

@joesavona I was wondering just that—the relationship between if/unless and
directives. Thanks for clarifying!

понедельник, 4 января 2016 г. пользователь Joseph Savona написал:

@dminkovsky https://github.com/dminkovsky RelayFragmentReference and
the if/unless functions on it aren't documented. The plan is to replace
these with standard GraphQL @include/@Skip directives.

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