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Is there another example than the one you provided? What I see in OutputExists/OutputNotExists is actually a Maybe/Option type. doSomething<Maybe<Output>>

by ljm 5y ago

Is there another example than the one you provided? What I see in OutputExists/OutputNotExists is actually a Maybe/Option type. doSomething<Maybe<Output>>(someObj) .map(({ url }) => url) .getOr(null) // value could either be url or null

015a 5y ago
Yeah my example was really just an Option type. A better example: think of Kubernetes API objects. In short, expressed as typescript interfaces: type KubeObject = Pod | Service; interface Pod { kind: "Pod", metadata: Metadata, spec: { containers: Container[] } }; interface Service { kind: "Service", metadata: Metadata, spec: { selector: ServiceSelector } }; const f = ({ kind, spec: { containers, selector } }: KubeObject) => {} So, the ability to destructure both 'spec.containers' and 'spec.selector' given just a KubeObject, and have the compiler use control flow analysis on 'kind' to mark one as 'never' or 'undefined' when its destructured on a type where it doesn't make sense.