Add a Computed Column - Nextedy Documentation

A computed column derives its content from a value expression instead of reading a stored property directly. Powersheet computes it in the browser every time the sheet renders. There are two kinds, and one character in the binding decides which you get:

a stored computed column writes its result back to the property it binds to, and
a display-only computed column stores nothing — it exists in the sheet and nowhere else.

Prerequisites

A working sheet configuration YAML file
A data model whose properties you want to compute from
Familiarity with dynamic value expressions (() => syntax)

Decide Whether the Value Should Be Stored

The binding key decides. A key prefixed with $ is unbound: it names a column, not a property.

Binding	`value`	Result
`total`	not set	Ordinary stored column — the user edits it
`total`	set	Computed and stored — the result is written to `total`, marks the row modified, and persists on save. Read-only to the user
`$total`	set	Computed and displayed only — nothing is stored, nothing is saved. Read-only to the user
`$total`	not set	Configuration error — an unbound column has nothing to derive its content from

value is about data; render and display are about appearance.Do not reach for render to avoid writing data — render styles whatever the cell already holds. If the value should never be stored, make the column unbound with $. If it should be stored, bind it to a real property.

Add a Stored Computed Column

Bind the column to a real property and give it a value expression. The result is written to that property, so it saves with the rest of the row:

columns:
  total:
    title: Total
    value: "() => context.entity.count * context.entity.rate"
    format: "c0$"

The user cannot type into the column — a computed column is read-only, because its content comes from the expression rather than from input. Editing count or rate recomputes it, marks the row modified, and the new total persists on the next save.

Add a Display-Only Computed Column

Prefix the binding key with $ to name a column that has no property behind it:

columns:
  $riskScore:
    title: Risk Score
    value: "() => context.entity.Probability * context.entity.Severity"
    valueType: number

Nothing is written anywhere. The column appears in the sheet, is read-only, and leaves the work item untouched — saving the row does not create or update a riskScore field.The $ marker belongs on the last segment only. Everything before it is an ordinary path that must resolve in the data model, and it decides which entity the column reads from:

columns:
  # derives from the root entity
  $riskScore:
    value: "() => context.entity.Probability * context.entity.Severity"

  # derives from the expanded system requirement
  systemRequirements.systemRequirement.$coverage:
    value: "() => context.entity.verifiedCount + ' / ' + context.entity.totalCount"

$total and total can coexist.The marker stays part of the column’s internal identity, so a display-only $total does not collide with a real total property in the same sheet. Give them different title values so readers can tell them apart.

If you leave title out, the header shows the name without the marker — $riskScore displays as riskScore.

Choose the Result Type

A display-only column has no metadata to take its type from, so declare it with valueType:

`valueType`	Use for	Notes
`string`	Text, labels, concatenations	The default when `valueType` is omitted
`number`	Scores, counts, sums, prices	Enables `format` and `aggregate`
`date`	Dates and date-times	Formats as `MMM dd, yyyy` unless `format` says otherwise

columns:
  $riskScore:
    title: Risk Score
    value: "() => context.entity.Probability * context.entity.Severity"
    valueType: number
    format: "n0"

  $reviewDue:
    title: Review Due
    value: "() => context.entity.approvedOn"
    valueType: date
    format: "yyyy-MM-dd"

valueType is for unbound columns only.A bound column takes its type from the data model, so declaring valueType on one is rejected. And because there is no metadata to consult, valueType: date cannot distinguish a date from a date-time — set format if you need the time part shown or hidden.

Total a Numeric Column in Group Rows

A numeric display-only column can be aggregated into group rows like any other numeric column:

columns:
  $riskScore:
    title: Risk Score
    value: "() => context.entity.Probability * context.entity.Severity"
    valueType: number
    aggregate: sum
    groupBy: true

aggregate requires valueType: number — declaring it on a text or date column is rejected.

Read the Row and the Level Above

Inside an unbound column’s value expression you can reach past the current entity:

Expression	Gives you
`context.entity`	The entity at the column’s own level — the one the binding path resolves to
`context.source`	The entity one level up, the one this level was navigated from
`context.row`	The whole row, as `context.row.entities[<level>]` across every level

columns:
  systemRequirements.systemRequirement.$origin:
    title: Origin
    value: "() => `${context.source.id} → ${context.entity.id}`"

context.value is empty in a value expression.A computed column has no stored cell value to start from, so context.value is undefined. Read the properties you need from context.entity instead.

What a Display-Only Column Cannot Do

A display-only column stores nothing and resolves no metadata, so several column properties do not apply to it. Each one is rejected outright rather than ignored:

Property	Why it is rejected
`isRequired`	The column is read-only and holds no stored data
`multiItem`	It binds no navigation property
`list`	The stages that resolve enumerations and references never run for it
`valueType` on a bound column	A bound column takes its type from the data model
`aggregate` without `valueType: number`	Only numeric derived values aggregate meaningfully

render, renderers, format, groupBy, sort, filter, columnGroup, and the styling properties all work normally.

Verify

After saving the configuration, do a full browser reload or re-open the document — the in-sheet refresh button reloads data, not the configuration. You should now see:

The computed column shows its derived value on every row
Clicking a cell does not enter edit mode, and pasting into the column changes nothing
Editing a property the expression reads updates the derived cell immediately
For a stored computed column, the row is marked modified and the value persists after save
For a display-only column, saving leaves the work item untouched
Grouping, sorting, filtering, sheet search, and Excel export all use the derived value

Grouping and sorting keep the keys they were built with.A derived cell repaints as soon as a property it reads changes, but an active grouping or sort is not rebuilt from the new values. Reload the sheet to regroup or resort on the updated keys.

Troubleshooting

Message	Cause
`The '$' marker is only allowed on the last segment.`	The marker is on a path segment other than the leaf
`The '$' marker needs a name (eg. '$riskScore').`	The binding is a bare `$` with nothing after it
`The path before '$<name>' does not resolve.`	The segments preceding the marker are not a valid path in the data model
`has no 'value' expression to derive its content from`	A `$`-prefixed column without a `value` expression
Column is blank on some rows	The row has no entity at that level. The expression still runs, but `context.entity` is `undefined` — guard with `?.`

​Prerequisites

​Decide Whether the Value Should Be Stored

​What a Display-Only Column Cannot Do

​Verify

​Troubleshooting

​See Also

Prerequisites

Decide Whether the Value Should Be Stored

What a Display-Only Column Cannot Do

Verify

Troubleshooting

See Also