Add suffix to each list member in helm template - kubernetes

Question

I'm trying to iterate over a list in a helm template, and add a suffix to each member.
I currently have this block of code that does exactly that:
{{- range $host := .Values.ingress.hosts }}
{{- $subdomain := initial (initial (splitList "." $host)) | join "." }}
{{- $topLevelDomain := last (splitList "." $host) }}
{{- $secondLevelDomain := last (initial (splitList "." $host)) }}
- host: {{- printf " %s-%s.%s.%s" $subdomain $environment $secondLevelDomain $topLevelDomain | trimSuffix "-" }}
{{- end }}
Since I need to do the exact same manipulation twice in the same file, I want to create a new list, called $host-with-env, that will contain the suffix I'm looking for. That way I can only perform this operation once.
Problem is - I've no idea how to create an empty list in helm - so I can't append items from the existing list into the new one.
Any idea how can I achieve this?
I'm also fine with altering the existing list but every manipulation I apply to the list seems to apply to the scope of the foreach I apply to it.
Any ideas how to go about this?

Answer 1

It might not be quite clear what result are you trying to achieve, it will be helpful to add your input, like your values.yaml and the desired output. However, I added an example that answers your question.
Inspired by this answer, you can use dictionary.
This code will add suffix to all .Values.ingress.hosts and put them into $hostsWithEnv dictionary into a list, which can be accessed by myhosts key
values.yaml
ingress:
hosts:
- one
- two
configmap.yaml
{{- $hostsWithEnv := dict "myhosts" (list) -}}
{{- range $host := .Values.ingress.hosts -}}
{{- $var := printf "%s.domain.com" $host | append $hostsWithEnv.myhosts | set $hostsWithEnv "myhosts" -}}
{{- end }}
apiVersion: v1
kind: ConfigMap
metadata:
name: my-configmap
data:
{{- range $hostsWithEnv.myhosts}}
- host: {{- printf " %s" . | trimSuffix "-" }}
{{- end }}
output
$ helm install --debug --dry-run .
[debug] Created tunnel using local port: '62742'
...
# Source: mychart/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: my-configmap
data:
- host: one.domain.com
- host: two.domain.com