Styjun

Let me preface this by saying I am not a javascript developer, so I'm probably missing something very obvious. I'm a data warehouse developer and creating a graphql server that can communicate with our DW got dropped in my lap.

I've been trying to get dataloaders to work on my graphql server by using a single object in the context, containing multiple dataloaders. I'm then trying to call the appropriate dataloader in the resolver. However, I've been unable to get this to work correctly. The consolidated dataloader object only works if I individually reference the dataloaders in the server context.

I'm trying to follow a similar pattern with the loaders as I have with my models, which is each broken out into a separate file, then consolidated for use as a single object via recursion through the file structure.

Example is I have an object called loaders which contains two loaders: countryLoader and marketsectorLoader, each of which is defined in a separate file under the "loaders" directory. In my server context, the following works

import * as loaders from "./loaders" 
graphQLServer.use('/graphql', bodyParser.json(), 
graphqlExpress({ 
schema,
context: { 
 countryLoader: loaders.countryLoader()

I can then call this in my resolver:

 StateProvince: 
Country: (parent, args, countryLoader) => 
 countryLoader.load(parent.Country_fkey) ,

This functions correctly, batching and returning the correct query result, but I'd prefer not to have to declare each specific dataloader from the loaders object as part of the context. However, I've been unable to figure out the syntax to use the loaders object in the context and call the appropriate
individual dataloader in the appropriate resolver.

I've tried several variants of the following example:
https://github.com/relay-tools/react-relay-network-layer/blob/master/examples/dataLoaderPerBatchRequest.js

which seems to be using the type of technique I'm trying to leverage:

//context snippet:
 context: 
request: req, // just for example, pass request to context
dataLoaders: initDataLoaders(),
 ,

However, no luck. I suspect the issue is with my resolver syntax, but I'm not sure, and I haven't been able to find working examples with multiple dataloaders.

If I'm reading your code correctly, importing your loaders using a wildcard import like this:

import * as loaders from './loaders'

results in an object wherein each property is a function that creates an instance of a particular DataLoader. So we just need to iterate through each property. For example:

// Using forEach
const dataLoaders = 
Object.keys(loaders).forEach(loaderName => 
 dataLoaders[loaderName] = loaders[loaderName]()
)

// Or using reduce
const dataLoaders = Object.keys(loaders).reduce((result, loaderName) => 
 result[loaderName] = loaders[loaderName]()
 return result
, )

Using lodash, you can also just do something like:

const dataLoaders = _.mapValues(loaders, loader => loader())