PrimaryKey

The PrimaryKey module defines a small protocol for values that can expose a stable, string-based identifier. A value participates by implementing a method at symbol; consumers can check unknown values with isPrimaryKey and read the key with value.

4 exports Since v2.0.0 Source

Getters

value

Since v2.0.0

Extracts the string value from a PrimaryKey.

When to use

Use to read the stable string identifier from a value that implements PrimaryKey.

Signature

declare function value(self: PrimaryKey): string

Example Reading primary key values

import { PrimaryKey } from "effect"

class OrderId implements PrimaryKey.PrimaryKey {
  constructor(private timestamp: number, private sequence: number) {}

  [PrimaryKey.symbol](): string {
    return `order_${this.timestamp}_${this.sequence}`
  }
}

const orderId = new OrderId(1640995200000, 1)
PrimaryKey.value(orderId) // => "order_1640995200000_1"

// Can also be used with simple string-based implementations
const simpleKey = {
  [PrimaryKey.symbol]: () => "simple-key-123"
}
PrimaryKey.value(simpleKey) // => "simple-key-123"

Guards

isPrimaryKey

Since v4.0.0

Checks whether a value implements the PrimaryKey protocol.

When to use

Use to narrow an unknown value before treating it as a PrimaryKey.

Details

This is a structural guard for the PrimaryKey.symbol property.

Gotchas

This guard does not call the method or verify that it returns a string.

See

PrimaryKey for the protocol being checked
value for extracting the string value after narrowing

Signature

declare function isPrimaryKey(u: unknown): u is PrimaryKey

Models

PrimaryKey

interface

Since v2.0.0

An interface for objects that can provide a string-based primary key.

When to use

Use to define values that expose a stable string identifier for equality, hashing, caching, or persistence.

Details

Objects implementing this interface must provide a method that returns a unique string identifier.

Signature

interface PrimaryKey {
  "~effect/PrimaryKey"(): string;
}

Example Implementing a primary key

import { PrimaryKey } from "effect"

class ProductId implements PrimaryKey.PrimaryKey {
  constructor(private category: string, private id: number) {}

  [PrimaryKey.symbol](): string {
    return `${this.category}-${this.id}`
  }
}

const productId = new ProductId("electronics", 42)
PrimaryKey.value(productId) // => "electronics-42"

Symbols

symbol

Since v2.0.0

Defines the unique identifier used to identify objects that implement the PrimaryKey interface.

When to use

Use to implement the PrimaryKey protocol as a computed property key on classes or object literals that expose a stable string identifier.

See

PrimaryKey for the protocol interface that declares the method keyed by this symbol
value for reading the string key from a PrimaryKey value
isPrimaryKey for checking whether an unknown value carries this method

Signature

declare const symbol: "~effect/PrimaryKey"