Dependents

Dependent properties are resolved automatically from other properties. Any external attempt to change their value is ignored; their value is solely modifiable through their resolver function.

Defining a dependent

A dependent field requires three rules:

• default: a value or function used as (or to generate) the default value
• dependsOn: at least one other property or virtual the field depends on
• resolver: a sync/async function that produces the new value when a dependency changes

import { Schema, type IvoSummary } from "ivo";

type Input = {
  firstName: string;
  lastName: string;
};

type Output = {
  firstName: string;
  fullName: string;
  lastName: string;
};

const userSchema = new Schema<Input, Output>({
  firstName: { required: true, validator: validateName },
  lastName: { required: true, validator: validateName },
  fullName: {
    default: "",
    dependsOn: ["firstName", "lastName"],
    resolver({ ctx: { firstName, lastName } }) {
      return `${firstName} ${lastName}`;
    },
  },
});

Note: The resolver runs after post-validation and virtual sanitizers. If the resolver throws during creation, the value becomes null; during an update, the property is ignored.

Default values

Dependent properties must have a default value. This value is used when the resolver has not yet run or when no dependencies are provided.

const schema = new Schema({
  total: {
    default: 0,
    dependsOn: ["price", "quantity"],
    resolver({ ctx }) {
      return ctx.price * ctx.quantity;
    },
  },
});

Readonly

Dependent properties can be made readonly with readonly: true. Once resolved, their value cannot be changed externally.

const schema = new Schema({
  completedAt: {
    default: "",
    readonly: true,
    dependsOn: "isComplete",
    resolver({ ctx }) {
      return ctx.isComplete ? new Date() : "";
    },
  },
});

Limitations

• Dependent properties cannot be required.
• They cannot have their own validator; validation should happen on the properties they depend on.

API summary

Option	Type	Required	Description
default	any | function	Yes	Default value or resolver for the property.
dependsOn	string | string[]	Yes	Property or properties the field depends on.
resolver	function	Yes	Function that computes the value when dependencies change.
readonly	true	No	Prevents external updates after the value is resolved.
onDelete	function | function[]	No	Handler(s) invoked when the model instance is deleted.
onSuccess	function | function[]	No	Handler(s) invoked after a successful create or update operation.