Helm pass single string to a template
there are multiple stackoverflow answers regarding passing multiple variables to a template in Helm, using dictionary.
However, I want to pass a single variable to a template. For example, I want to define template such as below, receiving input (a string to be exact).
{{- define "blahblah" $var }}
{{- if .Values.nameOverride }}
name: {{ .Values.nameOverride }}-$var
{{- else }}
name: $var
{{- end }}
{{- end }}
Thus, writing like below, I expect the result to be name: myname-whatever
or name:whatever
(assuming .Values.nameOverride
was defined as 'myname')
{{- include "blahblah" "whatever" }}
How can I let helm know which is the input variable to the template? Thank you!
Solution 1:
A Go text/template
template only accepts one parameter, and its value inside the template is the special variable .
. So you could, for example:
{{- define "name" -}}
name: {{ . }}
{{ end -}}
{{- template "name" "foo" -}}
name: foo
Or, you can pass in the Helm top-level object
{{- define "name-override" -}}
name: {{ .Values.nameOverride }}
{{ end -}}
{{- template "name-override" . -}}
Notice in this case that, inside the define
d template, we're referring to the Values
field of .
, and when we call it via template
, we're explicitly passing down .
as the parameter. Again, though, you only get one parameter.
Here you need two parameters: the Helm root value plus the additional value you're trying to pass in. I tend to use a list
to package the two parameters together into one value:
{{- define "blahblah" -}}
{{- $top := index . 0 -}}
{{- $var := index . 1 -}}
{{- if $top.Values.nameOverride -}}
name: {{- $top.Values.nameOverride -}}-{{ $var }}
{{ else -}}
name: {{ $var }}
{{ end -}}
{{- end -}}
{{ include "blahblah" (list . "whatever") | indent 2 }}
So the parameter to the template, when you call it, is a list; index . 0
is the first item out of .
, or the top-level Helm value, and index . 1
is the second item. The reverse of this is, since .
is a list, you need to qualify values that actually are part of the top-level Helm value with the variable name $top
that holds that value.