2020-12-15 12:27:38 +00:00
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*****
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Usage
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*****
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In order to perform conversions between currencies exchange rates must be
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defined.
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.. _Setting currency exchange rates:
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Setting currency exchange rates
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===============================
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All the `Currency <model-currency.currency>` values are relative.
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Best practice is to define which currency you want to use as the base currency
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by setting its exchange `Rate <model-currency.currency.rate>` to 1 for the
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date when it is first used.
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Then the rates of all other currencies are set as a multiplier of the base
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currency.
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In order to set an exchange rate of ``1.0 EUR = 1.1222 USD`` for the 1st of
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January the following records should be created:
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* A rate of ``1.0`` for the :abbr:`EUR (Euro)` currency with the 1st of
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January as the date.
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* A rate of ``1.1222`` for the :abbr:`USD (US Dollar)` currency with the 1st
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of January as the date.
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If you then wanted to update the exchange rate to ``1.0 EUR = 1.1034 USD`` for
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the 15th of January you just need to set the rate on the USD currency to
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``1.1034`` for that date.
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.. note::
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In this example, as there isn't any rate set for the dates between the 2nd
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and 14th of January the last available rate will be used.
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Here this rate would be ``1.1222`` as this was the rate set for the 1st of
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January.
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2021-02-21 19:31:10 +01:00
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.. _Scheduling rate updates:
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Scheduling rate updates
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=======================
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You may want to define some `Scheduled Rate Updates <model-currency.cron>` to
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keep the `Exchange Rates <model-currency.currency.rate>` up to date.
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When doing this you have to pick a source, the base `currency
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<model-currency.currency>` and a frequency.
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Then for each required date since the last update, a rate of ``1.0`` will be
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set for the base currency and the corresponding rate will be set for each of
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the selected currencies.
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.. warning::
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It is strongly advised to use the same base currency for all *Scheduled Rate
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Updates*.
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.. note::
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The currency module only supports the rates provided by the `European
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Central Bank`_, but third party modules can add additional sources for
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exchange rates.
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.. _European Central Bank: https://www.ecb.europa.eu/stats/policy_and_exchange_rates/euro_reference_exchange_rates/html/index.en.html
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