Helm3 Using Lookup Function to Load a Variable

I am currently attempting to use the lookup function via Helm 3.1 to load a variable during installation.

{{ $ingress := (lookup "v1" "Ingress" "mynamespace" "ingressname").status.loadBalancer.ingress[0].hostname }}

Of course, this returns, "bad character [." If I remove it, it returns "nil pointer evaluating interface {}.loadBalancer".

Is what I am attempting to do even possible?

Thanks

You are attempting to use "normal" array indexing syntax, but helm charts use "golang templates" and thus array indexing is done via the index function

{{ $ingress := (index (lookup "v1" "Ingress" "mynamespace" "ingressname").status.loadBalancer.ingress 0).hostname }}

after further thought, I can easily imagine that nil pointer error happening during helm template runs, since lookup returns map[] when running offline

In that case, you'd want to use the index function for every path navigation:

{{ $ingress := (index (index (index (index (index (lookup "v1" "Ingress" "mynamespace" "ingressname") "status") "loadBalancer")  "ingress") 0) "hostname") }}

or, assert the lookup is in "offline" mode and work around it:

      {{ $ingress := "fake.example.com" }}
      {{ $maybeLookup := (lookup "v1" "Ingress" "mynamespace" "ingressname") }}
      {{ if $maybeLookup }}
      {{   $ingress = (index $maybeLookup.status.loadBalancer.ingress 0).hostname }}
      {{ end }}