How to do nested <For

I have a signal that is array of arrays

  const [grid, setGrid] = createSignal([
    [1, 1, 1, 1, 1, 1, 1, 1],
    [1, 0, 0, 0, 0, 0, 0, 1],
    [1, 0, 0, 0, 0, 0, 0, 1],
    [1, 0, 0, 0, 0, 0, 0, 1],
    [1, 0, 0, 0, 0, 0, 0, 1],
    [1, 0, 0, 3, 0, 0, 0, 1],
    [1, 0, 0, 4, 0, 0, 0, 1],
    [1, 1, 1, 1, 1, 1, 1, 1],
  ])

  const [grid, setGrid] = createSignal([
    [1, 1, 1, 1, 1, 1, 1, 1],
    [1, 0, 0, 0, 0, 0, 0, 1],
    [1, 0, 0, 0, 0, 0, 0, 1],
    [1, 0, 0, 0, 0, 0, 0, 1],
    [1, 0, 0, 0, 0, 0, 0, 1],
    [1, 0, 0, 3, 0, 0, 0, 1],
    [1, 0, 0, 4, 0, 0, 0, 1],
    [1, 1, 1, 1, 1, 1, 1, 1],
  ])

I want to render it out on screen and for solid to update it. However I read https://www.solidjs.com/tutorial/flow_for and still not too sure how to do nested <For. I tried this:

  return (
    <main class="Main">
      <div class="boxWrapper">
        <For each={grid()}>
          {(row, i) => (
            <For each={row}>
              <div>{row}</div>
            </For>
          )}
        </For>
      </div>
    </main>

  return (
    <main class="Main">
      <div class="boxWrapper">
        <For each={grid()}>
          {(row, i) => (
            <For each={row}>
              <div>{row}</div>
            </For>
          )}
        </For>
      </div>
    </main>

But it doesn't work. In react it's quite simple, I just do

  return (
    <main class="Main">
      <div class="boxWrapper">
        {grid().map((row) => {
          return row.map((box) => {
            return <div class="box">{box}</div>
          })
        })}
      </div>
    </main>
  )

  return (
    <main class="Main">
      <div class="boxWrapper">
        {grid().map((row) => {
          return row.map((box) => {
            return <div class="box">{box}</div>
          })
        })}
      </div>
    </main>
  )

Thanks for any help.

SolidJS

Solid is a purely reactive library. It was designed from the ground up with a reactive core. It's influenced by reactive principles developed by previous libraries.

38 Replies

nikiv.devOP•3y ago

  return (
    <main class="Main">
      <div class="boxWrapper">
        <For each={grid()}>
          {(row, i) => {
            return (
              <>
                <For each={row}>
                  {(box) => {
                    return <div class="box">{box}</div>
                  }}
                </For>
              </>
            )
          }}
        </For>
      </div>
    </main>
  )

  return (
    <main class="Main">
      <div class="boxWrapper">
        <For each={grid()}>
          {(row, i) => {
            return (
              <>
                <For each={row}>
                  {(box) => {
                    return <div class="box">{box}</div>
                  }}
                </For>
              </>
            )
          }}
        </For>
      </div>
    </main>
  )

ok this works I think 🤔 I am not sure why the grid is not updating

nikiv.devOP•3y ago

https://github.com/nikitavoloboev/test/blob/main/solid-start/src/routes/snake.tsx#L18

GitHub

test/snake.tsx at main · nikitavoloboev/test

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nikiv.devOP•3y ago

https://github.com/nikitavoloboev/test/blob/main/solid-start/src/routes/snake.tsx#L74

GitHub

test/snake.tsx at main · nikitavoloboev/test

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nikiv.devOP•3y ago

I console logged, the values do change I can't console log inside the component function itself as it only runs once but I thought that if I render it out with jsx it would update

thetarnav•3y ago

imo you should use <Index> for that as the index is what's identifying the input element - not reference because changing 0 to 1 is changing the reference

nikiv.devOP•3y ago

        <Index each={grid()}>
          {(row) => {
            return (
              <>
                <Index each={row}>
                  {(box) => {
                    return <div class="box">{box}</div>
                  }}
                </Index>
              </>
            )
          }}
        </Index>

        <Index each={grid()}>
          {(row) => {
            return (
              <>
                <Index each={row}>
                  {(box) => {
                    return <div class="box">{box}</div>
                  }}
                </Index>
              </>
            )
          }}
        </Index>

something like this?

nikiv.devOP•3y ago

get some type errors

nikiv.devOP•3y ago

https://www.solidjs.com/docs/latest/api#index

SolidJS

Solid is a purely reactive library. It was designed from the ground up with a reactive core. It's influenced by reactive principles developed by previous libraries.

thetarnav•3y ago

Also, since the two components are to be derived from a single signal - both of them need to be subscribing to it So the nested <Index> should actually reference the signal as well in the each function

nikiv.devOP•3y ago

reading its docs it seems like its similar to For

thetarnav•3y ago

And thirdly, using a store would probably be the best

nikiv.devOP•3y ago

I have one component though so I put both snake and grid inside one store why doesn't it work with <For though

  const [state, setState] = createStore({
    grid: [
      [1, 1, 1, 1, 1, 1, 1, 1],
      [1, 0, 0, 0, 0, 0, 0, 1],
      [1, 0, 0, 0, 0, 0, 0, 1],
      [1, 0, 0, 0, 0, 0, 0, 1],
      [1, 0, 0, 0, 0, 0, 0, 1],
      [1, 0, 0, 3, 0, 0, 0, 1],
      [1, 0, 0, 4, 0, 0, 0, 1],
      [1, 1, 1, 1, 1, 1, 1, 1],
    ],
    snake: [],
  })

  const [state, setState] = createStore({
    grid: [
      [1, 1, 1, 1, 1, 1, 1, 1],
      [1, 0, 0, 0, 0, 0, 0, 1],
      [1, 0, 0, 0, 0, 0, 0, 1],
      [1, 0, 0, 0, 0, 0, 0, 1],
      [1, 0, 0, 0, 0, 0, 0, 1],
      [1, 0, 0, 3, 0, 0, 0, 1],
      [1, 0, 0, 4, 0, 0, 0, 1],
      [1, 1, 1, 1, 1, 1, 1, 1],
    ],
    snake: [],
  })

trying it with store

JCM•3y ago

When you call newSnake, line 155, you supply the same array (although some elements are mutated). The signal doesn't change if it's assigned a value that is equal to the old value (eg. same array) You can opt out of that with the createSignal options

JCM•3y ago

https://www.solidjs.com/docs/latest/api#createsignal

SolidJS

Solid is a purely reactive library. It was designed from the ground up with a reactive core. It's influenced by reactive principles developed by previous libraries.

nikiv.devOP•3y ago

then moveSnake(state, setState, direction) I get this I guess

JCM•3y ago

In my oppinion this has nothing to do with For vs Index

nikiv.devOP•3y ago

I have Q about this actually

JCM•3y ago

Using a store would solve the issue

nikiv.devOP•3y ago

reason I creates those mutable variables is that I can't do setStates there and expect changes to be instant they are not thats quite a big change if I move it to store hope it will solve it

function moveSnake(
  state: any,
  setState: (state: any) => void),
  direction: "up" | "down" | "left" | "right",
) {

function moveSnake(
  state: any,
  setState: (state: any) => void),
  direction: "up" | "down" | "left" | "right",
) {

I not sure how to type store well

JCM•3y ago

Check if `setSnake([...newSnake]) solves the issue. By cloning the array it should always notify the subscribers

nikiv.devOP•3y ago

so here

newSnake = [[rowOfHead, indexOfHead], ...snake]

newSnake = [[rowOfHead, indexOfHead], ...snake]

  if (snake.length > 0) {
    setSnake([[rowOfHead, indexOfHead], ...snake])
  } else {
    setSnake([[rowOfHead, indexOfHead]])
  }

  if (snake.length > 0) {
    setSnake([[rowOfHead, indexOfHead], ...snake])
  } else {
    setSnake([[rowOfHead, indexOfHead]])
  }

do this?

  if (snake.length > 0) {
    setSnake([[rowOfHead, indexOfHead], ...snake])
  } else {
    setSnake([[rowOfHead, indexOfHead]])
  }
  console.log(snake)

  if (snake.length > 0) {
    setSnake([[rowOfHead, indexOfHead], ...snake])
  } else {
    setSnake([[rowOfHead, indexOfHead]])
  }
  console.log(snake)

that console log there won't be updated value and I need new value of snake later in function or here

  setGrid(updatedGrid)
  setSnake(newSnake)

  setGrid(updatedGrid)
  setSnake(newSnake)

you mean should I continue with migration to store or that won't help

thetarnav•3y ago

https://playground.solidjs.com/anonymous/199dc4e8-65ae-476d-8236-3c6d6d2ee43e

Solid Playground

Quickly discover what the solid compiler will generate from your JSX template

JCM•3y ago

You can either create a new top level array with a spread, or alternatively use { equals: false } option on the signal to ensure it the signal fires each time the setter is called, even if it's the same array. The example of @thetarnav creates a copy with slice instead of spread, but it's similar

nikiv.devOP•3y ago

example of @thetarnav is blowing my mind a bit trying to make sense of it

thetarnav•3y ago

The secret is that I'm always calling grid() in each place it has to track it. Since this is a single signal, and you only reference some property of it without calling it, it won't track the change. Using createStore gives you that each property access is trackable

nikiv.devOP•3y ago

https://github.com/nikitavoloboev/test/blob/main/solid-start/src/routes/box.tsx

GitHub

test/box.tsx at main · nikitavoloboev/test

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nikiv.devOP•3y ago

I am now trying to

thetarnav•3y ago

So no component gets recreated, BUT all the places that call grid() will have to reexecute on each update to check if they don't have to update. So it's diffing, just smart diffing. Using createStore will eliminate that issue as well - you subscribe to a single value directly

nikiv.devOP•3y ago

move @thetarnav code to use my functions to update without store for now if I can as that would be a big diff so if I get it right it seems I can't pass setters to my function? like my moveSnake in the end it should just update the signal value then DOM should change as signal value is updated im confused why it doesn't 😐 I checked that logic is valid if I just console log updatedGrid and newSnake at end like the grid has right values and all I will try to add things on top of @thetarnav code instead of combining

thetarnav•3y ago

those will be the same references

nikiv.devOP•3y ago

ohh ok but if I don't do it and say do set things instantly how do I get current updated values inside same function

thetarnav•3y ago

const newValue = setSignal(p => ...)

const newValue = setSignal(p => ...)

? But I would just destructure the top-level signal values and apply the change

nikiv.devOP•3y ago

ok will try thank you like Big Thief too btw 🙂

thetarnav•3y ago

this is the first time I saw a function that takes both value and the setter 😄

thetarnav•3y ago

I would never pass the setter around

nikiv.devOP•3y ago

yea it did look ugly I just thought thats how you had to do it like im coming from react that would work in react or well you can actually have the function inside component so you don't need to pass it too

thetarnav•3y ago

I mean I like to have a single place where the state is updated, then it gets confusing where the change actually happens, is it batched or not, idk oh I missed that ❤️ ngl I have yours "Inspired" playlist often on repeat

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How to do nested <For

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