cursorForObjectInConnection uses indexOf method about graphql-relay-js

[almeynman]

Ok. I will explain what I was trying to do: Suppose I have list of items. I want to make a RANGE_ADD mutation. In mutateAndGetPayload function I receive inputs and save new Item to db, then I return this item:

mutateAndGetPayload: async (input, { rootValue }) => {
    const item = new Item({
      text: input.text,
    });
    await item.save();
    return { item };
  },

In outputFields resolve function I fetch previously fetched items

outputFields: {
    itemEdge: {
      type: ItemEdgeType,
      resolve: async ({ item }) => {
        const array = await ItemModel.orderBy(...);
        ....

Here I want to return

return {
          cursor: cursorForObjectInConnection(array, item),
          node: item,
        };

however cursorForObjectInConnection has indexOf in place, so it returns null, as item saved in mutateAndGetPayload is not the same object as the item in array, although they have exactly same properties and values.

So I have to manually find this Item in array to pass it to cursorForObjectInConnection, i.e.

outputFields: {
    itemEdge: {
      type: ItemEdgeType,
      resolve: async ({ item }) => {
        const array = await ItemModel.orderBy(...);
        let itemToPass;
        for (const i of array) {
          if (i.id === item.id) {
            itemToPass = item;
          }
        }
        return {
          cursor: cursorForObjectInConnection(array, itemToPass),
          node: itemToPass,
        };

SO I need to iterate and find an item in order for indexOf method to iterate correctly. It's not a big deal, I just don't like how the code looks

[wincent]

I don't think we'd want to add a dependency on lodash, as we've intentionally kept the dependency footprint small (note that we only depend on babel-runtime).

If you can provide a bit more detail about what you're trying to achieve, and maybe some sample code, we could suggest ways to make it easier to do what you want.

[bmcmahen]

I have the same problem. Perhaps an optional callback to provide our own equality conditions would suffice, or simply a third argument to specify the index of the matching node. I think the main problem is moreso silent failure when the nodeList and node come from two separate sources.

[athibaud]

i've had this problem myself... indeed it mostly arrises when nodeList and node come from seperate sources therefore the objects are equal in value but not in reference.. so indexOffails.

plus it's a real pity to have to pass trough the list twice (once to find our node in the nodeList and once again in cursorForObjecttInConnection with indexOf to find the index of that node in the same nodeList...)

@bmcmahen's callback solution seems reasonable but seeing all cursorForObjecttInConnection does is return offsetToCursor(index) wouldn't it be simpler to just expose offsetToCursor and let the user deal with finding the index ?

[wincent]

@athibaud:

wouldn't it be simpler to just expose offsetToCursor and let the user deal with finding the index

I'd be ok with this, especially seeing as its inverse, cursorToOffset, is already exposed.

@bmcmahen, @almasakchabayev: Would that address your use case?

[bmcmahen]

Yup, that sounds good to me.

[athibaud]

@wincent 👍

[almeynman]

@wincent that solves the problem