Passthrough Custom Scalars?

[AlexaderDNT]

Is it possible to use custom scalars for Graphql? Is it activated in the project

[nerdsupremacist]

Hi! Yes it is supported to some extent. It's not been tested very heavily though. Custom scalars right now are always mapped to String.

If you want to use a custom type for it there's a GraphQLScalar protocol you can use. But make sure to make the Scalar typealias to String. Otherwise it won't work.

Here's for example how it works with URL:

extension URL: GraphQLScalar {
    typealias Scalar = String

    static let placeholder: URL = URL(string: "https://graphaello.dev/assets/logo.png")!

    private struct URLScalarDecodingError: Error {
        let string: String
    }

    init(from string: Scalar) throws {
        guard let url = URL(string: string) else {
            throw URLScalarDecodingError(string: string)
        }
        self = url
    }
}

And in your structs you will have to specify that it's the type that you want:

struct MyStuct {
    @GraphQL(MyAPI.path.to.url)
    var url: URL
}

If you try this out, please let me know how it goes. I would love to improve this feature.

I have considered having some config files (yaml or json) to make this work better, but it felt like a weird addition that didn't fit in with the rest. It would make it easier to enforce that all urls are treated equally, though

[AlexaderDNT]

Getting this error

[nerdsupremacist]

Alright. So this Scalar is definitely not encoded as a string. Not to worry. I'll come up with something for it ;)

I think the best way to configure this is to include the scalar mappings in the API.json and use the CLI to configure it.

Something like:

# Outputs Scalars and Compatible Swift Types (Checking for Conformance to GraphQLScalar)
graphaello scalars list
# Sets Scalar of Point to always be interpreted as a Coordinate 
graphaello scalars set --api MyApi --graphql Point --swift Coordinate

[AlexaderDNT]

Sounds good :)