implement sql.Scanner and driver.Value for graphql.ID type

[nicksrandall]

This makes graphql.ID type implement sql.Scanner and driver.Valuer. This simplifies the data structures that I'm using so that they can implement the types that graphql likes but can also be marshaled into the DB.

[nicksrandall]

@neelance @bsr203 What do you think of this small change? Do you think it would be useful to others?

[bsr203]

@nicksrandall sorry, I don't use sql backend but could see it may useful for others.

[neelance]

What about this: Have your own type ID string and give it those methods. Use it in your struct. Then cast to graphql.ID in the resolver of the id field.

[nicksrandall]

Having to always cast to graphql.ID is what I'm trying to avoid. Currently my structs use strings for ID prop and I have to cast to graphql.ID in resolvers. I use strings for the DB. This change would allow me to not have to worry about casting in all the right places.

This also allows me to use the same struct for resolvers as input type because input type requires ID type (to be idiomatic).

I imagine that anybody using this lib with a SQL backend would find this helpful. Am I wrong?

What are your concerns with adding this?

[dmitshur]

I imagine that anybody using this lib with a SQL backend would find this helpful. Am I wrong?

Would everyone who uses this library and a SQL backend want this exact implementation, or would their needs differ slightly?

[nicksrandall]

Anybody using the sql package in the standard lib would need this exact implementation.

EDIT: I can't say that definitively. My guess is that this would cover a large majority of people using the standard sql package.

[neelance]

I still think that it is beneficial to have a clear separation between resolver API and underlying data structures. The resolvers are a view/projection on the underlying data. To me it feels like your change would mix this up a bit.

On the other hand I see that there currently is a strict 1-to-1 coupling between the GraphQL type ID and the Go type graphql.ID. This is inflexible and contradicts the freedom you have with resolver types.

One option would be to accept any named string type as a GraphQL ID. But that would also allow a pure string, which I dislike.

There might be some good solution around custom resolvers. You could use any type as the result type for ID, but that type would need to provide a method to turn the value into something GraphQL understands. The type would also check at startup if it is compatible with the given GraphQL type. The same method could be used for Time and for custom behavior like #28 and #17. I have to think about it some more.

[nicksrandall]

What I have ended up doing is adding my own custom scalar type ID that is a named string that implements the sql methods that I need.

[neelance]

@nicksrandall Please take a look at 2b513d7 and #3 (comment). This should be a proper solution here.

[nicksrandall]

I like it! Thanks @neelance. I close this PR

[binajmen]

@nicksrandall Please take a look at 2b513d7 and #3 (comment). This should be a proper solution here.

@nicksrandall @neelance First of all, thank you for your work!!

Sorry to dig in the past, but could you please explain me how I can apply the proposed solution to my case? I'm using SQL with IDs defined as integers.

As a new gopher, It's not clear where and how I should implement this..

[binajmen]

I ran into the same situation regarding the scalar Time. I solved it at the moment by editing graphql-go/time.go (BUT this should be avoided of course!!):

// Value implements the driver Valuer interface
func (t Time) Value() (driver.Value, error) {
	return t.Time, nil
}

// Scan implements the Scanner interface.
func (t *Time) Scan(src interface{}) error {
	return t.UnmarshalGraphQL(src)
}

This offers me the possibility to use this same struct for GraphQL and GORM:

type Question struct {
	ID       int32  `gorm:"primary_key"`
	Question string `gorm:"not null"`
	...
	CreatedAt graphql.Time
}

However, I'd really like to apply your proposition (using UnmarshalGraphQL I suppose?), but I don't understand how to do so..