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How it works...

Let's open the project CurrencyRatesCalculator.dproj. The GUI is quite simple and is shown here:

Figure 5.8: CurrencyRatesCalculator GUI

The first problem we have to cope with is: how many, and which currency types, will be available in the combo? Well, we'll use a nice, free RESTful service to get the conversion rates available at https://exchangeratesapi.io/, and this service has a set of APIs to interact with. For instance, to get the latest foreign exchange reference rates in JSON format, we can call the following request:

GET https://exchangeratesapi.io/api/latest

This obtains the following response (rates are quoted against ...

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