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Mixins

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Define a set of fields to be shared across content types.

Introduction

Horizontal inheritance is a programming concept where fields can be reused across different objects. Mixins make it possible to dynamically extend existing existing content types with additional fields.

A Mixin may be added to all, or a specified list of content types. For instance, the SEO Meta fields application makes use of this, so editors may fine-tune SEO settings across all different content they produce. Also, Mixins may be explicitly enabled or made optional, so the editors may ensable or disable the mixin on a per content item basis.

In Content Studio, mixins are visualized as a separate tabs in the content editor.

Usage

The file with mixin schema must be placed in the folder cms/mixins/[name] and called [name].yaml. For example, site/mixins/address/address.yaml.

address.yaml
kind: "Mixin"
title: "Full address"
form:
  - type: "TextLine"
    name: "addressLine"
    label: "Street address"
    occurrences:
      min: 0
      max: 2
  - type: "TextLine"
    name: "city"
    label: "City"
    occurrences:
      min: 1
      max: 1
  - type: "TextLine"
    name: "zipCode"
    label: "Zip code"
    occurrences:
      min: 1
      max: 1
  - type: "TextLine"
    name: "country"
    label: "Country"
    occurrences:
      min: 1
      max: 1

Activation

A mixin schema on its own is dormant — it must be registered in the application’s CMS descriptor (cms.yaml) before it is applied to content. The descriptor controls whether the mixin is mandatory or editor-toggleable, and whether it is restricted to specific content types via regex.

Output

Mixin content is stored in the content under the key x (short for miXin).

To avoid conflict between mixins from different namespaces, the namespace is used as a prefix. For example, if you have the namespace com.company, with a mixin called address containing a field city, the value of that field will be stored and searchable x.com-company.address.city.

The JSON structure of the mixin content will look like this:

{
  "x": {
    "com-company": {
        "address": {
            "city": "Oslo"
        }
    }
  }
}
Namespaces are transformed by replacing dots with dashes. So com.company becomes com-company. This is done to ensure that the keys are valid for content querying.

GraphQL

When querying content with mixins via the GraphQL API, the mixin fields are available under the x field. For example, to query the JSON structure shown above, you would use the following GraphQL query:

{
  guillotine {
    query(key: "contentid") {
      x {
      	com_company {
          address {
          	city
          }
        }
      }
    }
  }
}
Due to GraphQL field naming restrictions (- and . are not allowed), dots are replaced with underscores. So com.company becomes com_company.

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