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one

$one​

A constraint that checks whether exactly one of the provided processors returns a defined value.

Returns the single defined value, or throws if zero or more than one succeed. Be careful to not use this in a situation where the provided processors may require late-resolved values! This works best in finalizers, validators, or in opaque schema transformers.

See $exclusive if you want to check for truthiness instead of a defined value.

Parameters​

  • processors (Array<ProcessorSpec>, required): Array of processor specifications, exactly one of which must return a defined value.

Example​

// Exactly one authentication method must be configured
new Schema('object').validator({
  $one: [
    {$property: 'apiKey'},
    {$property: 'oauth'},
    {$property: 'basicAuth'},
  ]
})