Comments (6)
This is intentional, when querying against a Union you must narrow the type by using a fragment.
{
product {
... on Good {
title
}
}
}
This ensures that your query will be resilient to the evolution of the type schema over time. When this client has shipped, and you introduce a new type into your Product
union, your client can safely ignore those additional typed items. If you were to query a field without first specifying the concrete Object type, then a new type could be added which happens to have a title
field and now your existing client is overfetching and potentially rendering incorrectly.
If title
is a critical part of what a Product
is, such that you want to guarantee that you can always query title
regardless of what concrete Object type is in use, then you should use an Interface instead of a Union.
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Found the solution — GraphQLInterfaceType
should be used to union object types.
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Can you please write an example? I get cannot query field {name}
error no matter what I do when I call on common fields. Should I always call with fragments?
{
product {
title // common fields (all types)
... on Good {
// other fields
}
}
}
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@vslinko Thanks to this I know what you mean now.
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It would be great to be able to opt out of this intentional safety check. In some apps where e.g. the same developer or team works the full stack then the better tradeoff for them might be that they can select on common fields of the union type. Yes it will crash if the union is extended by the server, but the queries are flatter/easier to make. Assuming there is only one right answer here for all apps and teams is not ideal IMO.
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Looks like if all types in a union implement an interface, containing the common fields, you can then query those common fields by narrowing to that interface.
interface CommonFields {
name: String
}
type TypeA implements CommonFields {
name: String
fieldA: String
}
type TypeB implements CommonFields {
name: String
fieldB: String
}
union TypeAll = TypeA | TypeB
Then you can query a field of type TypeAll
like this
{
field {
...on CommonFields {
name
}
}
from graphql-js.
Related Issues (20)
- refactor(src): remove `.js` extension, append it for compiled files
- RangeError: Maximum call stack size exceeded in OverlappingFieldsCanBeMergedRule
- Uncaught SyntaxError: missing name after . operator HOT 1
- FieldResolver performance HOT 1
- Inline fragment from an interface to an interface that extends it is invalid
- Resource exhaustion exploit when parsing queries HOT 7
- In GraphQL how to set WriteOnce functionality in specific property in the collection schema
- Generator generates alias imports not compatible with TypeScript Type-Only Imports and verbatimModuleSyntax HOT 2
- Printing the @oneOf directive HOT 1
- Allow shallow sorting with lexicographicSortSchema HOT 2
- Passing arguments into the resolvers by just using `buildSchema` and `graphql`? HOT 3
- Error after upgrading from 16.6 to 16.8.1 with globalThis.process.env.NODE_ENV HOT 12
- Add: Link to new api docs in the README of this project.
- Introspection result missing interfaces
- Detect subscription successfully started
- Errors thrown when iterating over subscription source event streams (AsyncIterables) should be caught HOT 1
- graphql resolver circular dependency type error (bi-directional relation) HOT 1
- Current main is up to 50% slower than previous major version HOT 10
- Type definition for `DefinitionNode` appears to be wrong HOT 4
- AST: `IntValueNode` and `FloatValueNode` store values as string HOT 2
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