Update MLXChatExample for iOS Sandboxing

[rudrankriyam]

On iOS, due to sandboxing, using the default hub gives an error along the line because it cannot store in the downloads directory:

You do not have permission to save the file "model-name" in the folder "mlx-community"

We can directly use the default parameter of HubApi() that stores under the documents directory, accessible on both iOS and macOS.

Also, I wonder the need for the default static value then?

/// Extension providing a default HubApi instance for downloading model files
extension HubApi {
    /// Default HubApi instance configured to download models to the user's Downloads directory
    /// under a 'huggingface' subdirectory.
    static let `default` = HubApi(
        downloadBase: URL.downloadsDirectory.appending(path: "huggingface"))
}

Thank you creating this example @ibrahimcetin!

[rudrankriyam]

On second thoughts, would you prefer a OS dependent approach? Keep desired behavior of downloads folder on macOS, while documents for the rest OSes.

[ibrahimcetin]

I’ve added this because my Documents directory syncs with iCloud, which caused all Hugging Face models to sync to my iCloud account. I didn’t test this on iOS, so I didn’t notice the issue earlier.

For now, using this workaround might be a better approach:

#if(os(macOS))
static let `default` = HubApi(
        downloadBase: URL.downloadsDirectory.appending(path: "huggingface"))
#elseif(os(iOS))
static let `default` = HubApi()
#endif

Later, we can improve the handling of this in HubApi for a more robust solution.

[rudrankriyam]

Let's do it #else only so it takes care of visionOS as well

[ibrahimcetin]

Thank you.

I think HubApi should use HF_HOME if configured or default huggingface path as a default on macOS. What do you think @rudrankriyam?

[rudrankriyam]

I think the HF_HOME is for the token, and not the path to store the download? For a sample project, I would prefer keeping it to default and let the developers update the path according to their needs. What do you say?