I'm new to Helm.

I have a default value in parent chart. I want to use this value in each subchart by default, but also to have a possibility to override the value for a specific subchart.

Example:

# Parent-chart values.yaml

global:
  schedule: 10m

All the subcharts will use this value by default. But if I run something like this:

helm install --set subchart-A.schedule="20m"

Subchart-A will use value "20m".

I'm thinking about two possibilities:

1. Maybe I can somehow link subchart-value to global value:

# Subchart values.yaml

schedule: {{ .Values.global.schedule }} # it doesn't work

In that case, it would be possible to override a specific value for the single subchart.

2. Maybe I can write a function

# Pseudocode:

if subchart.schedule is null
  printf global.schedule
else
  printf subchart.schedule

What would you do and what is generally possible?