collectype / factory/objects/objectInstanceType / objectInstanceTypeFactory
objectInstanceTypeFactory<
T,C>(ctx,oper): <K>(field) =>C
Defined in: factory/objects/objectInstanceType.ts:40
Creates a predicate filter for object instance types using PredicType.object.instanceType.
T
The item type in the collection.
C extends Wherable<T, C>
The Wherable context type (must extend Wherable<T, C>).
C
The context (usually a collection) supporting the where method.
ObjectInstanceTypeOper
The instance type operation to perform (see PredicType.object.instanceType).
Returns a function that takes a field (of type object on T) and applies the object instance type predicate to filter the context.
<
K>(field):C
K extends string | number | symbol
K
C
// Example: Composing an object instance type filter as a property, homogeneous model
import { BaseFunctions } from 'collectype';
import { objectInstanceTypeFactory } from 'collectype';
type Person = { name: string; meta: object };
class PersonFunctions extends BaseFunctions<Person> {
objectIsType = objectInstanceTypeFactory<Person, this>(this, 'Date');
}
// Usage:
const people: Person[] = [
{ name: 'Alice', meta: new Date() },
{ name: 'Bob', meta: {} },
{ name: 'Eve', meta: [] }
];
const fn = new PersonFunctions(people);
const filtered = fn.objectIsType('meta');
// filtered contains the items where 'meta' is of type Date
PredicType.object.instanceType for type checks on object fields.