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world-money/Modules/`world-common`/Formatting

Formatting

The world.format.Formatter trait provides a generic interface for converting types to string representations.

The Formatter Trait

trait Formatter[A]:
  extension (a: A)
    def formatted: String

Overview

The world.format.Formatter trait defines an extension method formatted for any type A, providing a consistent interface for string conversion.

Using Formatters

Types that implement world.format.Formatter can be formatted using the formatted extension method:

import world.format.Formatter
import world.money.*
import world.money.currency.Currencies

val amount = Money[Currencies.KES.type](1000.50)
val text = amount.formatted  // Uses Formatter[Money[Currencies.KES.type]]

Note: The method is formatted, not format.

Built-in Formatter Instances

The library provides world.format.Formatter instances for standard types:

  • Formatter[String]
  • Formatter[Int]
  • Formatter[Long]
  • Formatter[BigDecimal]
  • Formatter[Double]
  • Formatter[Float]
  • Formatter[Boolean]

Additional instances are provided for domain types, including:

Implementing Custom Formatters

Implement world.format.Formatter for your own types:

import world.format.Formatter
import world.money.*
import world.money.currency.Currencies

case class Product(id: String, name: String, price: Money[Currencies.GBP.type])

given Formatter[Product] with
  extension (product: Product)
    def formatted: String =
      s"${product.id}: ${product.name} - £${product.price.value.unwrap}"

val product = Product("WIDGET-1", "Premium Widget", Money[Currencies.GBP.type](29.99))
product.formatted  // "WIDGET-1: Premium Widget - £29.99"

Formatter Composition

Formatters compose naturally:

import world.format.Formatter
import world.money.*
import world.money.currency.Currencies

case class Invoice(items: List[Money[Currencies.KES.type]], total: Money[Currencies.KES.type])

given Formatter[Invoice] with
  extension (invoice: Invoice)
    def formatted: String =
      val itemsStr = invoice.items.map(_.formatted).mkString(", ")
      s"Items: [$itemsStr] Total: ${invoice.total.formatted}"

Formatting vs. toString

The formatted method is distinct from toString:

  • toString - Provides a debug-friendly representation
  • formatted - Provides a user-facing representation
import world.money.*
import world.money.currency.Currencies

val amount = Money[Currencies.GBP.type](100)

amount.toString   // "Money(CurrencyValue(100))"
amount.formatted  // User-facing format

Locale-Aware Formatting

The world.format.Formatter abstraction is not locale-aware. This is a major limitation for locale-specific formatting requirements it is highly likely that this will be moved to world-locale in a later release.

API Reference

See world.format.Formatter for the complete API.

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