Theo's Typesafe Cult•2y ago

Best way to validate multiple files via Zod & RHF

So I am adding validation to a form and I want to validate as much as possible on the frontend. Now I do believe some validation needs to be done by the backend, but I'll handle that after I've figured out what already has been validated by the frontend. The things I want to validate are the following: - The user has selected/uploaded at least 3 files for the form ~~- The files are of a accepted file type~~ - The combined size of all files does not exceed a certain threshold My initial thought was to just add the following to the form schema:

image: z.any().array().min(3, { message: "At least 3 files are required" }),

image: z.any().array().min(3, { message: "At least 3 files are required" }),

But the files are not in an array, they are instead bundled in an object like so:

"image": {
        "0": {},
        "1": {},
        "2": {}
    }

"image": {
        "0": {},
        "1": {},
        "2": {}
    }

So the first hurdle becomes how do I translate this into a Zod shape? This doesn't work

image: z.object({string: z.string(), fileBlob: z.any()})

image: z.object({string: z.string(), fileBlob: z.any()})

And is there a better way to select a specific file and perform operations, eg: formInput.image?.[1].type The data comes from a simple input

<input
  type="file"
  multiple
  {...register("image")}
  disabled={isSubmitting}
  accept=".jpg, .jpeg, .png, .webp, .mp4"
/>

<input
  type="file"
  multiple
  {...register("image")}
  disabled={isSubmitting}
  accept=".jpg, .jpeg, .png, .webp, .mp4"
/>

Most of the examples I've seen online are mainly focused around single files and make the assumption that formInput.image?.[0] exists.

8 Replies

Neto•2y ago

You can use preprocess on zod to transform the object into an array

cornflour•2y ago

for the first part of the question, maybe use z.record?

Neto•2y ago

Or You can parse on the submit handler to pass only the array

Mordi•2y ago

yeah records seems to make things a lot simpler The most advanced Zod things I've looked into are .refine and .superrefine, how would the .preprocess look? .preprocess((val) => ???

Neto•2y ago

the type T is just a lazy way of casting where are the 'data' and z.string() you would change for the file and etc

Neto•2y ago

Mordi•2y ago

I see , thanks for the help!

Neto•2y ago

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Best way to validate multiple files via Zod & RHF