# iOS Client cannot upload file to Back-end server

**URL:** <https://community.apollographql.com/t/ios-client-cannot-upload-file-to-back-end-server/1128>\
**Category:** Client SDKs\
**Tags:** client, mobile, ios\
**Created:** [August 18, 2021, 12:33am UTC](https://community.apollographql.com/t/ios-client-cannot-upload-file-to-back-end-server/1128 "2021-08-18T00:33:15Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![pie\_nguyen](https://sea1.discourse-cdn.com/flex019/user_avatar/community.apollographql.com/pie_nguyen/32/750_2.png) [@pie\_nguyen](https://community.apollographql.com/u/pie_nguyen)\
**Post date:** [August 18, 2021, 12:33am UTC](https://community.apollographql.com/t/ios-client-cannot-upload-file-to-back-end-server/1128/1 "2021-08-18T00:33:16Z")

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I need to upload an image from iOS Client to NestJS server  
Here is the munation

```auto
createSellerProfile(seller: SellerInput, userId: ID!, uploads: Upload): Seller

```

iOS Client’s .graphql file:

```auto
mutation createSellerProfile($seller: SellerInput, $userId: ID!, $uploads: Upload) {
    createSellerProfile (seller: $seller, userId: $userId, uploads: $uploads) {
        id
        firstName
        lastName
    }
}

```

And this is the client’s code

```auto
let avaimg = avatarImage.jpegData(compressionQuality: 0.1)

let file = GraphQLFile(fieldName: "avatar", originalName: "avatar", mimeType: "image/jpeg", data: avaimg)
        
let sellerData = SellerInput(firstName: "phuong", lastName: "nguyen", description: "Hello, this is Phuong. I am freelance web developer")
        
Network.shared.apollo.upload(operation: CreateSellerProfileMutation(seller: sellerData, 
userId: "4d146299-a219-4bde-9874-bed936dda129", uploads: "avatar"), files: [file]) {
       res in
       switch (res) {
       case .success(let graphQLResult):
            print("success")
       case .failure(let error):
            print("error: \(error)")
       }
}

```

But on my NestJS server, I only receive a single string “avatar” for my uploads field instead of file content. Please help me out, thank you.

---

<div class="post-metadata">

**Author:** ![hwillson](https://sea1.discourse-cdn.com/flex019/user_avatar/community.apollographql.com/hwillson/32/9_2.png) [@hwillson](https://community.apollographql.com/u/hwillson)\
**Post date:** [August 18, 2021, 12:26pm UTC](https://community.apollographql.com/t/ios-client-cannot-upload-file-to-back-end-server/1128/2 "2021-08-18T12:26:52Z")

</div>

It looks like you’re passing the string “avatar” to your mutation for the `uploads` argument, which explains why you’re getting that on the server. You probably want to pass your `file` object in as `uploads` instead.

> [@pie\_nguyen](#):
>
> ```auto
> CreateSellerProfileMutation(seller: sellerData, 
> userId: "4d146299-a219-4bde-9874-bed936dda129", uploads: "avatar")
> 
> ```

For more details see: [https://www.apollographql.com/docs/ios/mutations/#uploading-directly-with-apollo](https://www.apollographql.com/docs/ios/mutations/#uploading-directly-with-apollo)

---

<div class="post-metadata">

**Author:** ![pie\_nguyen](https://sea1.discourse-cdn.com/flex019/user_avatar/community.apollographql.com/pie_nguyen/32/750_2.png) [@pie\_nguyen](https://community.apollographql.com/u/pie_nguyen)\
**Post date:** [August 18, 2021, 1:55pm UTC](https://community.apollographql.com/t/ios-client-cannot-upload-file-to-back-end-server/1128/4 "2021-08-18T13:55:42Z")

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> **[Performing mutations](https://www.apollographql.com/docs/ios/mutations/)**

I followed the guide here and the example as well. It says the Upload is underhood the string param. But it doesnt seem to work idk why

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**Author:** ![designatednerd](https://sea1.discourse-cdn.com/flex019/user_avatar/community.apollographql.com/designatednerd/32/28_2.png) [@designatednerd](https://community.apollographql.com/u/designatednerd)\
**Post date:** [August 18, 2021, 2:59pm UTC](https://community.apollographql.com/t/ios-client-cannot-upload-file-to-back-end-server/1128/5 "2021-08-18T14:59:26Z")

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Hugh, unfortunately this is correct for Web but not for iOS.

TL;DR - you need to make the `fieldName` be `"uploads"` when you create the `GraphQLFile` rather than `"avatar"` because it has to match the name of the field name in the `createSellerProfile` mutation in GQL.

The long version:

This is something that is unfortunate about generating type-safe code: You can’t just pass in the different type when it actually makes sense to do so.

In this case, `Upload` is defined as a custom scalar, whose underlying value is `String`. That means all the parameters in Swift that want an `Upload` actually take a `String`, and all the parameters that want an `[Upload]` want an array of `String`. You can’t just hand a `GraphQLFile` in when a parameter is expecting a `String`, because it won’t compile.

The way we work around this is to hand the actual files you want to upload over to the networking client via the `files` parameter of the `upload` operation. Then, using each file’s `fieldName` property, we set up a multipart-form request that actually uploads each of the files for the appropriate field.

This is why the `fieldName` has to match the name of the GraphQL field it’s being uploaded for in the schema: So that particularly in circumstances where we have several files being passed in, we know which file(s) are for which field(s) and we can map them properly.

Is this more complicated than it should be for developers? Oh yes! The problem is that “fixing” it would involve special-casing code generation for `Upload` scalars, which would be very, very difficult in our current codegen (and frankly would still probably be difficult in our forthcoming Swift-based codegen, which is still under construction).

This is why in the docs [we actually recommend using a purpose-built uploader](https://www.apollographql.com/docs/ios/mutations/#an-important-caveat-about-file-uploads) if you can, and only passing the URL string of the location where the file was uploaded via GraphQL.

It’s a lot easier to hide all this detail under the covers in Javascript, where there isn’t a type system being enforced. I think that’s where @hwilson got caught up, as that’s his area of expertise.

Hope that all helps!

---

<div class="post-metadata">

**Author:** ![hwillson](https://sea1.discourse-cdn.com/flex019/user_avatar/community.apollographql.com/hwillson/32/9_2.png) [@hwillson](https://community.apollographql.com/u/hwillson)\
**Post date:** [August 18, 2021, 3:04pm UTC](https://community.apollographql.com/t/ios-client-cannot-upload-file-to-back-end-server/1128/6 "2021-08-18T15:04:53Z")

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Haha - in my case I just misread the docs that I even included in my response! 🤦‍♂️ Thanks for the correction @designatednerd!

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<div class="post-metadata">

**Author:** ![pie\_nguyen](https://sea1.discourse-cdn.com/flex019/user_avatar/community.apollographql.com/pie_nguyen/32/750_2.png) [@pie\_nguyen](https://community.apollographql.com/u/pie_nguyen)\
**Post date:** [August 18, 2021, 3:29pm UTC](https://community.apollographql.com/t/ios-client-cannot-upload-file-to-back-end-server/1128/7 "2021-08-18T15:29:31Z")

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worked beautifully, thank you so much

---

<div class="post-metadata">

**Author:** ![hwillson](https://sea1.discourse-cdn.com/flex019/user_avatar/community.apollographql.com/hwillson/32/9_2.png) [@hwillson](https://community.apollographql.com/u/hwillson)\
**Post date:** [August 18, 2021, 3:31pm UTC](https://community.apollographql.com/t/ios-client-cannot-upload-file-to-back-end-server/1128/8 "2021-08-18T15:31:15Z")

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Closed on August 18, 2021, 3:31pm UTC

Solved.