Since you are using array in your values.yaml file, please see related issue

Alternative solution

• Your values.yaml is missing values for args and env. I've set them in my example, as well as changed indent to 14

• Your cronjob.yaml server: "{{ $job.image.server }}" value is null, and I've changed it to .image.nfsserver

Instead of using array, just separate your services like in example below:

values.yaml

jobs:
  myservice:
    namespace: default
    image:
      repository: xxx.com/myservice
      tag: fe4544
      pullPolicy: Always
      secret: xxx
      nfslogpath: "/var/logs/"
      nfsserver: "xxx"
      nfspath: "/nfs/xxx/cronjobs/"
      nfsreadonly: false
      env:
        key: val
    schedule: "*/5 * * * *"
    args:
      key: val
    failedJobsHistoryLimit: 1
    successfulJobsHistoryLimit: 3
    concurrencyPolicy: Forbid
    suspend: false

  myservice2:
    namespace: default
    image:
      repository: xxxx/myservice2
      tag: 1dff39a
      pullPolicy: IfNotPresent
      secret: xxxx
      nfslogpath: "/var/logs/"
      nfsserver: "xxxx"
      nfspath: "/nfs/xxx/cronjobs/"
      nfsreadonly: false
      env:
        key: val
    schedule: "*/30 * * * *"
    args:
      key: val
    failedJobsHistoryLimit: 1
    successfulJobsHistoryLimit: 2
    concurrencyPolicy: Forbid
    suspend: false

In your cronjob.yaml use {{- range $job, $val := .Values.jobs }} to iterate over values.

Use $job where you used {{ $job.name }}.

Access values like suspend with {{ .suspend }} instead of {{ $job.suspend }}

cronjob.yaml

{{- $chart_name := .Chart.Name }}
{{- $chart_version := .Chart.Version | replace "+" "_" }}
{{- $release_name := .Release.Name }}

{{- range $job, $val := .Values.jobs }}
---
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  namespace: {{ .namespace }} 
  name: "{{ $release_name }}-{{ $job }}"
  labels:
    chart: "{{ $chart_name }}-{{ $chart_version }}"
spec:
  concurrencyPolicy: {{ .concurrencyPolicy }}
  failedJobsHistoryLimit: {{ .failedJobsHistoryLimit }}
  suspend: {{ .suspend }}
  jobTemplate:
    spec:
      template:
        metadata:
          labels:
            app: {{ $release_name }}
            cron: {{ $job }}
        spec:
          containers:
          - image: "{{ .image.repository }}:{{ .image.tag }}"
            imagePullPolicy: {{ .image.imagePullPolicy }}
            ports:
              - name: http
                containerPort: 80
                protocol: TCP
            name: {{ $job }}
            args:
{{ toYaml .args | indent 14 }}
            env:
{{ toYaml .image.env | indent 14 }}
            volumeMounts:
            - name: nfs
              mountPath: "{{ .image.nfslogpath }}"
          restartPolicy: OnFailure
          imagePullSecrets:
            - name: {{ .image.secret }}
          volumes:
            - name: nfs
              nfs:
                server: "{{ .image.nfsserver }}"
                path: "{{ .image.nfspath }}"
                readOnly: false
  schedule: {{ .schedule | quote }}
  successfulJobsHistoryLimit: {{ .successfulJobsHistoryLimit }}
{{- end }}

Passing values using --set :

helm upgrade cronjobs cronjobs/ --wait --set jobs.myservice.image.tag=b70d744

Example:

helm install --debug --dry-run --set jobs.myservice.image.tag=my123tag .

...
HOOKS:
MANIFEST:

---
# Source: foo/templates/cronjob.yaml
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  namespace: default
  name: "illmannered-iguana-myservice"
  labels:
    chart: "foo-0.1.0"
spec:
  concurrencyPolicy: Forbid
  failedJobsHistoryLimit: 1
  suspend: false
  jobTemplate:
    spec:
      template:
        metadata:
          labels:
            app: illmannered-iguana
            cron: myservice
        spec:
          containers:
          - image: "xxx.com/myservice:my123tag"
            imagePullPolicy:
            ports:
              - name: http
                containerPort: 80
                protocol: TCP
            name: myservice
            args:
              key: val

            env:
              key: val

            volumeMounts:
            - name: nfs
              mountPath: "/var/logs/"
          restartPolicy: OnFailure
          imagePullSecrets:
            - name: xxx
          volumes:
            - name: nfs
              nfs:
                server: "xxx"
                path: "/nfs/xxx/cronjobs/"
                readOnly: false
  schedule: "*/5 * * * *"
  successfulJobsHistoryLimit: 3
---
# Source: foo/templates/cronjob.yaml
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  namespace: default
  name: "illmannered-iguana-myservice2"
  labels:
    chart: "foo-0.1.0"
spec:
  concurrencyPolicy: Forbid
  failedJobsHistoryLimit: 1
  suspend: false
  jobTemplate:
    spec:
      template:
        metadata:
          labels:
            app: illmannered-iguana
            cron: myservice2
        spec:
          containers:
          - image: "xxxx/myservice2:1dff39a"
            imagePullPolicy:
            ports:
              - name: http
                containerPort: 80
                protocol: TCP
            name: myservice2
            args:
              key: val

            env:
              key: val

            volumeMounts:
            - name: nfs
              mountPath: "/var/logs/"
          restartPolicy: OnFailure
          imagePullSecrets:
            - name: xxxx
          volumes:
            - name: nfs
              nfs:
                server: "xxxx"
                path: "/nfs/xxx/cronjobs/"
                readOnly: false
  schedule: "*/30 * * * *"
  successfulJobsHistoryLimit: 2

Hope that helps!