today checking some of the amplify documentation (I know this one says it is a preview in the iOS scenario) but I have ran into a road block.
Assumptions
- Amplify is correctly configured in my iOS project. I can push data to
Personand query theAmplify.API - The schema has been defined as:
type Person @model {
id: ID!
name: String!
possessions: [Thing] # list of things this person owns.
@connection(keyName: "byPerson", fields: ["id"])
}
type Thing @model
@key(name: "byPerson", fields: ["personId"]) {
id: ID!
name: String!
personId: ID!
ownerOfThings: Person # defining the 'belongsTo' property.
@connection(fields: ["personId"])
}
This generates the following code:
public struct Person: Model {
public let id: String
public var name: String
public var possessions: List<Thing>?
public init(id: String = UUID().uuidString,
name: String,
possessions: List<Thing>? = []) {
self.id = id
self.name = name
self.possessions = possessions
}
}
public struct Person: Model {
public let id: String
public var name: String
public var ownerOfThings: Person?
public init(id: String = UUID().uuidString,
name: String,
ownerOfThings: Person? = nil) {
self.id = id
self.name = name
self.ownerOfThings = ownerOfThings
}
}
Here is where I ran into trouble. Amplify.API doesn't seem be saving my object and its associated data in a single mutation. I have to call it as nested operations to have an effect.
// sample on how I am trying to save data.
var thing = Thing(name: "Long Claw")
let person = Person(
name: "Jon Snow",
possessions: List([ thing ])
)
Amplify.API.mutate(of: person, type: .create) { ev in
// doing something with the event.
print(String(describing: ev)) // this works. It saves the instance to DynamoDB
// unfortunately, it did not save the instance of thing... let's try to correct this.
thing.ownerOfThings = person
Amplify.API.mutate(of: thing, type: .create) { ev2 in
// do something else with this...
print(String(describing: ev2))
// this ^ crashes badly...
}
}
The code above will generate an output similar to:
Result.success(Person(id: "EC4BEEE1-C1A1-4831-AB86-EA1E22D8AD48", name: "Jon Snow", possessions: nil))
GraphQLResponseError<Thing>: GraphQL service returned a successful response containing errors: [Amplify.GraphQLError(message: "Variable \'input\' has coerced Null value for NonNull type \'ID!\'", locations: Optional([Amplify.GraphQLError.Location(line: 1, column: 26)]), path: nil, extensions: nil)]
I've tried declaring the relationship as:
type Person @model {
id: ID!
name: String!
possessions: [Thing] # list of things this person owns.
@connection(keyName: "byPerson", fields: ["id"])
}
type Thing @model
@key(name: "byPerson", fields: ["personId"]) {
id: ID!
name: String!
personId: ID!
# ownerOfThings: Person
# @connection(fields: ["personId"]) # Not belongsTo for you!
}
Or a variation of this, defining the possessions as possessions: [Thing] @connection.
All of them generate various (although some what related) errors, preventing me from storing my data.
So, the question is: How do you specify the relationship in iOS to save it?
