Join field

Show related documents that link to the current document, such as the posts in a category.

Use field.Join to show documents that link to the document being read. For example, a category can list all posts whose category relationship points to it. Ridu finds these posts when you read the category, so you do not have to maintain a second list of IDs.

In the admin

A populated Articles in this category Join field in the Ridu admin showing the related article row.

The category shows the posts that currently link to it.

List the posts in a category

content/categories.go

var Categories = ridu.Collection{
  Slug: "categories",
  Fields: field.Fields{
    field.Text("name").Required(),
    field.Join("posts", "posts", "category"),
  },
}

var Posts = ridu.Collection{
  Slug: "posts",
  Fields: field.Fields{
    field.Text("title").Required(),
    field.Relationship("category", "categories"),
  },
}

The three arguments are the field name to return (posts), the collection to search (posts), and the relationship to follow (category). That relationship must point to one document in the current collection; relationships to several documents or collection types are not supported.

Configuration

Constructor or method	What it controls
`field.Join(name, collection, on)`	Finds target documents whose `on` relationship points back to the current document.
`.Limit(n)`	Bounds rows returned and shown for this join.
`.DefaultColumns(paths...)`	Chooses the target fields shown in the admin table.
`.DefaultSort(path)`	Sets the initial target sort; prefix the path with `-` for descending order.
`.AllowCreate(true)`	Lets an author create and link a target document from the join UI.
`.Access(...)` / `.RestrictAccess(...)`	Controls whether the computed join appears in a response.
`.AfterRead(...)`	Transforms the returned join output without adding stored data.

Join is computed from the target relationship. It has no default, requiredness, write hook, or stored column on the current document.

Configure the admin view

content/categories.go

field.Join("posts", "posts", "category").
  Limit(20).
  DefaultColumns("title", "status", "updatedAt").
  DefaultSort("-updatedAt").
  AllowCreate(true)

Limit accepts 1 through 100. Use DefaultColumns and DefaultSort to configure the table, and AllowCreate to let authors create a related document from it. DefaultSort must name a sortable path of the target collection; a group, list, has-many, JSON or plugin field fails configuration with invalid_join_sort. Authors still need read or create access to the target collection. Joins must live at a collection root and are not supported on globals.

The value appears in generated output but never in create/update input. Reads apply target access, hooks, localization, and field redaction. Select output fields to omit an expensive join when a consumer does not need it. Use SDK mutateJoin for an explicit atomic addition/removal; it updates the target documents’ forward relationships through validation and access.

Common mistakes

Do not create and manually synchronize a second forward relationship.
AllowCreate(true) shows a create button; it does not grant create permission.
Changing the collection or relationship path changes which documents the Join returns.

See field.Join and Relationships and joins.