PropertyAccessor

PropertyAccessor<T> describes a callback that reads a value from an instance of T. Use it when an API accepts a property-selection function instead of a property name string.

The generic parameter checks the callback’s input: with PropertyAccessor<Customer>, TypeScript knows which properties a customer has. It does not constrain the result to a particular property type, because the return type is any. Specify T rather than relying on the default object when you need member completion and property-name checking.

export type PropertyAccessor<T = object> = (instance: T) => any;

Use this type when you need strongly-typed property-selection callbacks.

Example

import { PropertyAccessor } from '@cratis/fundamentals';

type Customer = {
    id: string;
    name: string;
};

const getName: PropertyAccessor<Customer> = customer => customer.name;

const value = getName({ id: '1', name: 'Sample customer' });

Common Usage

This is a type alias, not a runtime wrapper. Calling the accessor executes your function against the instance you supply; it does not create an instance, check incoming data, or handle missing nested objects. For an optional nested value, put the required guard or optional chaining in the callback itself.

PropertyAccessorDescriptor pairs an accessor with an explicit array of path segments. Its path property joins those segments with dots; the descriptor does not infer them from the callback. Keep the segments consistent with the property your callback reads when constructing a descriptor.

For an API that must retain the selected value’s type, use a more specific callback signature such as (instance: Customer) => string rather than expecting this alias to preserve that result type.

See also

• Constructor — accept a runtime class rather than an instance callback
• Field decorator — describe runtime field types for serialization