Definitions
In CUE, schemas are typically written as Definitions.
A definition is a field which identifier starts with
#
or _#
.
This tells CUE that they are to be used for validation and should
not be output as data; it is okay for them to remain unspecified.
A definition also tells CUE the full set of allowed fields.
In other words, definitions define “closed” structs.
Including a ...
in struct keeps it open.
schema.cue
#Conn: {
address: string
port: int
protocol: string
// ... // uncomment this to allow any field
}
lossy: #Conn & {
address: "1.2.3.4"
port: 8888
protocol: "udp"
// foo: 2 // uncomment this to get an error
}
$ cue export schema.cue
{
"lossy": {
"address": "1.2.3.4",
"port": 8888,
"protocol": "udp"
}
}