Working with predefined lenses

In this recipe, we will work with predefined lenses. We will use a library lens-aeson for dealing with JSON data. The aeson library is a popular library for parsing and writing JSON instances for the user-defined data. Often, we have to deal with JSON, and parse it on the fly to extract the desired data.

Getting ready

In this recipe, we will use the generic JSON parser provided by aeson, and then use lens-aeson to dig through the JSON to extract the data.

How to do it...

1. Create a new project, working-with-aeson-lens, with a simple stack template.

        stack new working-with-aeson-lens simple

2. Add a dependency on the lens library in the build-depends sub-section of the executable section. Also add dependency on aeson and lens-aeson libraries. Also add bytestring and text, as aeson uses bytestring for parsing and text for string values. Add vector, as we need to work with arrays in JSON:

 executable working-with-aeson-lens
   hs-source-dirs:      src
   main-is: ...