Accessing nested array in Formik FieldArray

Question

**EDIT: Please check the updated sandbox, it incorporates some of the changes suggested in the below answer. **

I'm using Formik and its <FieldArray ../> component to handle some nested data to render inputs. I can't quite figure out what exact string to pass to the name prop in <FieldArray name={ // here}.

In my component I have a user selection that filters out some data and returns this array.

"chosenDevice": [
  {
    "deviceName": "eth0",
    "macAddress": "01:40:27:0F:2E:CB",
    "ipv4DHCP": false,
    "ipv4Addresses": [
      "182.148.1.100/24"
    ],
    "ipv4Gateway": "",
    "ipv6DHCP": false,
    "ipv6Addresses": [
      "232.232.2/100/10"
    ],
    "ipv6Gateway": ""
  }
]

I want to access the ipv4Addresses array. I'm either passing the wrong string to name or not using index in .map properly. Currently I have the following:

    <FieldArray
  name={`chosenDevice.ipv4Addresses[${index}]`}
>
  {({ remove, push }) => (
    <>
      <div>
        {values.chosenDevice.length > 0 &&
          values.chosenDevice.map(
            (ipv4Addresses, index) => (
              <div
                style={{
                  display: "flex"
                }}
                key={index}
              >
                <label
                  htmlFor={`chosenDevice[${index}].ipv4Addresses`}
                  className="custom-label"
                  style={{ flex: 1 }}
                >
                  ipv4Address(es)
                  <Field
                    className="custom-input"
                    name={`chosenDevice[${index}].ipv4Addresses`}
                    placeholder="< ipv4Address >"
                    type="text"
                  />
                </label>
                <ErrorMessage
                  name={`chosenDevice.${index}.ipv4Addresses`}
                  component="div"
                  className="field-error"
                />

I have a codesanbox that may provide some more context.

After looking into this further, basically I need to provide the string value of deviceName[0].ipv4Addresses[0], so I may need to rethink the .map and what it's actually returning.

Answer 1

With a .map inside of another .map, you might be getting index values confused. Try naming index something more specific to each .map (such as deviceIndex and addressIndex). I've used addressIndex for the inner map operation in my answer below.

---

It seems like your <FieldArray> here should only concern itself with the ipv4Addresses array on the current chosenDevice object.

Try this:

<FieldArray
  name="chosenDevice.ipv4Addresses"
>
  {({ remove, push }) => (
    <>
      <div>
        {chosenDevice.ipv4Addresses > 0 &&
          chosenDevice.ipv4Addresses.map(
            (ipv4Address, addressIndex) => (
              <div
                style={{
                  display: "flex"
                }}
                key={addressIndex}
              >
                <label
                  htmlFor={`chosenDevice.ipv4Addresses.${addressIndex}`}
                  className="custom-label"
                  style={{ flex: 1 }}
                >
                  ipv4Address(es)
                  <Field
                    className="custom-input"
                    name={`chosenDevice.ipv4Addresses.${addressIndex}`}
                    placeholder="< ipv4Address >"
                    type="text"
                  />
                </label>
                <ErrorMessage
                  name={`chosenDevice.ipv4Addresses.${addressIndex}`}
                  component="div"
                  className="field-error"
                />

But if I'm wrong about that, and the <FieldArray> tag does need to reference which chosenDevice it's a child of, this should do it:

<FieldArray
  name={`chosenDevice.${index}.ipv4Addresses`}
>
  {({ remove, push }) => (
    <>
      <div>
        {chosenDevice[index].ipv4Addresses > 0 &&
          chosenDevice[index].ipv4Addresses.map(
            (ipv4Address, addressIndex) => (
              <div
                style={{
                  display: "flex"
                }}
                key={addressIndex}
              >
                <label
                  htmlFor={`chosenDevice.${index}.ipv4Addresses.${addressIndex}`}
                  className="custom-label"
                  style={{ flex: 1 }}
                >
                  ipv4Address(es)
                  <Field
                    className="custom-input"
                    name={`chosenDevice.${index}.ipv4Addresses.${addressIndex}`}
                    placeholder="< ipv4Address >"
                    type="text"
                  />
                </label>
                <ErrorMessage
                  name={`chosenDevice.${index}.ipv4Addresses.${addressIndex}`}
                  component="div"
                  className="field-error"
                />

Answer 2

<FieldArray name={`chosenDevice.ipv4Addresses[${index}]`}>

The index here if you are trying to use from the map below, then this is wrong you'll not get index outside the map.

Use this map above the FieldArray, like this:

values.chosenDevice.map((ipv4Addresses, index) => (
 <FieldArray
  name={`ipv4Addresses[${index}]`}
>
  {({ remove, push }) => (
    <>
      <div>
              <div
                style={{
                  display: "flex"
                }}
                key={index}
              >
                <label
                  htmlFor={`chosenDevice[${index}].ipv4Addresses`}
                  className="custom-label"
                  style={{ flex: 1 }}
                >
                  ipv4Address(es)
                  <Field
                    className="custom-input"
                    name={`chosenDevice[${index}].ipv4Addresses`}
                    placeholder="< ipv4Address >"
                    type="text"
                  />
                </label>
                <ErrorMessage
                  name={`chosenDevice.${index}.ipv4Addresses`}
                  component="div"
                  className="field-error"
                />)