Loops with Maps

tip

We recommend reviewing Go Templates documentation before attempting to create a template.

If you're new to YAML we also recommend reviewing the YAML 1.2 spec for validation on syntax.

Overview

From Go template range:

{{range pipeline}}
  T1
{{end}}

The value of the pipeline must be an array, slice, map, or channel. If the value of the pipeline has length zero, nothing is output; otherwise, dot is set to the successive elements of the array, slice, or map and T1 is executed. If the value is a map and the keys are of basic type with a defined order, the elements will be visited in sorted key order.

tip

For information on range/else statements see conditional docs

Sample

Let's take a look at ranging over a map for a template:

metadata:
  template: true

steps:

  {{ range $key, $value := .images }}

  - name: test{{ $key }}
    commands:
      - go test ./...
    image: {{ $value }}
    {{ .pull_policy }}
    ruleset:
      event: [ push, pull_request ]

  {{ end }}

  - name: build
    commands:
      - go build
    environment:
      CGO_ENABLED: '0'
      GOOS: linux
    image: golang:latest
    {{ .pull_policy }}
    ruleset:
      event: [ push, pull_request ]

The caller of this template could look like:

version: "1"
templates:
  - name: sample
    source: github.com/<org>/<repo>/path/to/file/<template>.yml
    type: github

steps:
  - name: golang
    template:
      name: sample
      vars:
        pull_policy: "pull: always"
        images:
          _latest: golang:latest
          _1.13: golang:1.13
          _1.12: golang:1.13

Which means the compiled pipeline for execution on a worker is:

warning

Go does not guarantee order with maps. If you need the steps to always be outputted in the same order use the loops with slice implementation.

version: "1"
steps:
  - name: sample_test_latest
    commands:
      - go test ./...
    image: golang:latest
    pull: always
    ruleset:
      event: [ push, pull_request ]

  - name: sample_test_1.13
    commands:
      - go test ./...
    image: golang:1.13
    pull: always
    ruleset:
      event: [ push, pull_request ]

  - name: sample_test_1.12
    commands:
      - go test ./...
    image: golang:1.12
    pull: always
    ruleset:
      event: [ push, pull_request ]

  - name: sample_build
    commands:
      - go build
    environment:
      CGO_ENABLED: '0'
      GOOS: linux
    image: golang:latest
    pull: always
    ruleset:
      event: [ push, pull_request ]