Conditional fields

Use a field condition when one authoring control should appear only after another value makes it relevant. Conditions react immediately in the admin. They do not remove data, reject API input, or grant access.

field.Sibling creates one typed condition. Attach it to the field being shown with field.ShowWhenCondition:

field.Text(
  "videoURL",
  field.ShowWhenCondition(
    field.Sibling("format", field.ConditionEquals, "video"),
  ),
)

Read that expression as: “show videoURL when the format field beside it equals video.”

Start with string equality

field.ShowWhen(path, value) is the concise form for one sibling string equality. This complete collection reveals videoURL when an author chooses the Video format:

package content

import (
  "github.com/riducms/ridu"
  "github.com/riducms/ridu/field"
)

var Posts = ridu.Collection{
  Slug: "posts",
  Fields: []field.Definition{
    field.Text("title", field.Required()),
    field.Select(
      "format",
      field.OneOf("article", "video"),
      field.Default("article"),
    ),
    field.Text(
      "videoURL",
      field.ShowWhen("format", "video"),
    ),
  },
}

Use ShowWhen for this common string case. Use Sibling with ShowWhenCondition for booleans, numbers, several accepted values, negation, or combined rules.

Understand sibling scope

A sibling path starts at the parent of the field being shown:

• A root field reads another root field.
• A field inside a Group reads from that Group.
• A field inside an Array or Block reads from its own row, not another row.
• A sibling path can descend through non-repeating Groups, such as settings.kind.
• It cannot cross through an Array or Blocks field. Ridu rejects that path while resolving the configuration.

The following condition is attached to answers.explanation. For the third answer row, field.Sibling("settings.kind", ...) reads answers.2.settings.kind. The separate field.Document("archived", ...) predicate always reads the root archived field:

package content

import (
  "github.com/riducms/ridu"
  "github.com/riducms/ridu/field"
)

var Questions = ridu.Collection{
  Slug: "questions",
  Fields: []field.Definition{
    field.Checkbox("archived", field.Default(false)),
    field.Array("answers", field.Fields(
      field.Group("settings", field.Fields(
        field.Select("kind", field.OneOf("lesson", "question", "note")),
      )),
      field.Textarea(
        "explanation",
        field.ShowWhenCondition(field.All(
          field.Sibling("settings.kind", field.ConditionOneOf, "lesson", "question"),
          field.Not(field.Document("archived", field.ConditionEquals, true)),
        )),
      ),
    )),
  },
}

At the document root, Sibling("status", ...) and Document("status", ...) read the same value. Prefer Sibling when the rule should remain relative if those fields later move together into a Group or repeated row. Use Document when the rule intentionally depends on a root setting.

Choose an operator

The comparison value must have the same scalar type as the referenced field. Ridu checks paths, types, and operand counts before the application starts.

Strings, booleans, and numbers are supported. For example:

field.Sibling("featured", field.ConditionEquals, true)
field.Sibling("score", field.ConditionNotEquals, 0)
field.Sibling("status", field.ConditionOneOf, "draft", "review")

Combine predicates with field.All, field.Any, and field.Not. All and Any require at least two children; Not wraps exactly one.

Conditions are presentation only

A hidden field keeps its current form value and can still be submitted through REST, the SDK, or the Local API. This prevents toggling a controller field from silently deleting work, but it also means a condition is never a security or validation rule.

Use the corresponding server contract when behavior must be enforced:

See reading sibling values for those contexts and the complete row-scoped field access example.

Troubleshooting

• If a nested condition reads the wrong value, confirm that the controlling field shares the same Group, Array row, or Block with the field being shown. Use field.Document for a root value.
• If a condition never matches, check that the comparison type matches the referenced field. The boolean true is different from the string "true".
• If ShowWhen cannot express the comparison, switch to ShowWhenCondition and a typed Sibling predicate.
• If an API caller can still write the hidden field, add field access or a hook. That behavior is intentional.

See field.Sibling, field.Document, field.ShowWhenCondition, and field.ShowWhen for their exact signatures.