Class: OpenExchangeRatesClient

Inherits:
Object
  • Object
show all
Defined in:
lib/open_exchange_rates_client.rb

Overview

Client for the Open Exchange Rates API (https://openexchangerates.org).

Replaces the unmaintained money-historical-bank git gem, whose
money (~> 6) gemspec pin blocked the money 7.x upgrade. That gem's
Money::Bank surface (exchange_with, import_rates/export_rates,
the in-memory rate store) went entirely unused — ExchangeRate
only ever needed a single historical-rate lookup, which is all this
class provides.

OXR quotes every currency against USD, so an arbitrary pair reduces
to rates[to] / rates[from] with USD pinned at 1.0.

Constant Summary collapse

BASE_URL = 
'https://openexchangerates.org/api'
REQUEST_TIMEOUT = 
15

Instance Method Summary collapse

Constructor Details

#initialize(app_id: ENV.fetch('OPENEXCHANGERATES_APP_ID', nil)) ⇒ OpenExchangeRatesClient

Returns a new instance of OpenExchangeRatesClient.

Parameters:

  • app_id (String, nil) (defaults to: ENV.fetch('OPENEXCHANGERATES_APP_ID', nil)) —

    OXR application id; defaults to the
    OPENEXCHANGERATES_APP_ID env var.



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# File 'lib/open_exchange_rates_client.rb', line 20

def initialize(app_id: ENV.fetch('OPENEXCHANGERATES_APP_ID', nil))
  @app_id = app_id
end

Instance Method Details

#rate(date, from, to) ⇒ Float?

Exchange rate from from to to effective on date.

Parameters:

  • date (Date) —

    rate date; today uses OXR's /latest endpoint,
    earlier dates use /historical.

  • from (String, Symbol) —

    ISO 4217 code to convert from

  • to (String, Symbol) —

    ISO 4217 code to convert to

Returns:

  • (Float, nil) —

    the rate, or nil when OXR has no usable
    data for date (or either currency is absent from the response)



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# File 'lib/open_exchange_rates_client.rb', line 32

def rate(date, from, to)
  from = from.to_s.upcase
  to = to.to_s.upcase
  return 1.0 if from == to

  rates = rates_for(date)
  return nil if rates.blank?

  from_rate = from == 'USD' ? 1.0 : rates[from]
  to_rate   = to == 'USD' ? 1.0 : rates[to]
  return nil unless from_rate && to_rate

  to_rate.to_f / from_rate
end