slint-ui/slint · error · TypeError

setRowData is not implemented on this model

Error message

setRowData is not implemented on this model

What it means

Base Model's default setRowData throws because a generic model has no way to store data; subclasses must override it to support mutation. The runtime calls this when .slint code assigns to a model row. Throwing rejects the modification loudly instead of silently dropping it.

Solutions

  1. Override setRowData(row, data) in your Model subclass to persist the new value.
  2. If the model must be read-only, change the .slint usage so rows are not assigned to.
  3. Switch to ReadOnlyModel/ArrayModel, which implements setRowData over its backing array.

Example fix

// before
class MyModel extends slint.Model { rowCount() { return 1; } rowData(i) { return 'x'; } }
// after
class MyModel extends slint.Model {
  rowCount() { return 1; }
  rowData(i) { return 'x'; }
  setRowData(row, data) { this.data[row] = data; }
}
Defensive patterns

Strategy: try-catch

Validate before calling

if (model.setRowData === slint.Model.prototype.setRowData) throw new Error('model is read-only');

Type guard

function isEditableModel<T>(m: slint.Model<T>): boolean {
  return m.setRowData !== slint.Model.prototype.setRowData;
}

Try / catch

try {
  model.setRowData(row, value);
} catch (e) {
  if (e instanceof TypeError && /setRowData is not implemented/.test(e.message)) {
    console.warn('model is read-only; change ignored');
  } else throw e;
}

Prevention

When it happens

Trigger: Slint code (e.g. property assignment on a model row) or JS code calls setRowData(row, data) on a model instance that did not override setRowData.

Common situations: Using a read-only custom Model subclass in an editable context (text input bound to model data), forgetting to implement setRowData when making a model two-way editable.

Related errors

AI-assisted analysis of slint-ui/slint@bb937076de (2026-09-16). Data as JSON: /api/errors/bb3a8a1d4ad0ef10. Report an issue: GitHub.

Appendix: source

Thrown at api/node/typescript/models.ts:134

     * Implementations of this function must return the current number of rows.
     */
    abstract rowCount(): number;
    /**
     * Implementations of this function must return the data at the specified row.
     * @param row index in range 0..(rowCount() - 1).
     * @returns undefined if row is out of range otherwise the data.
     */
    abstract rowData(row: number): T | undefined;

    /**
     * Implementations of this function must store the provided data parameter
     * in the model at the specified row.
     * The default implementation throws, rejecting the modification.
     * @param _row index in range 0..(rowCount() - 1).
     * @param _data new data item to store on the given row index
     */
    setRowData(_row: number, _data: T): void {
        throw new TypeError("setRowData is not implemented on this model");
    }

    /**
     * Adds a line to the model with the provided data.
     * Throws when the model rejects the modification.
     * The default implementation calls {@link Model.insertRow} with the row count.
     * @param data new data item to store in a new row.
     */
    pushRow(data: T): void {
        this.insertRow(this.rowCount(), data);
    }

    /**
     * Implementations of this function must remove the row at the specified index.
     * Throws when the model rejects the modification; the default implementation
     * always throws.
     * @param _index index of the row to remove.
     */

View on GitHub (pinned to bb937076de)