mnachury/solidexercices

Some exercices around some principles of SOLID

Solid Exercices

The goal is to implement a digital calculator from strings.

WARNING: do not change naming of classes, it would break the code at some point.

Here are the proposed exercices:

• First we want to implement the Calculator that can calculate simple operations: sums, products, substractions and divisions
  • A first test is given for sum, don't forget to write some for additional cases and other operations
  • Try to avoid exceptions with explicit messages if impossible to calculate
  • Q1: what can you do to avoid lots of ifs or a switch?
• If it is not the case, remove any conditions about the operation to apply
  • Q2: what is the core concept of object-oriented programmation you are using?
• If it is not the case, make your calculator not aware of concrete operations it supports
  • Q3: what is the principles you are applying in this case?
• Then, we have a CalculatorTrainer class (and a console application using it) that run several operations stored in an array against Calculator
  • NB: you need to include the CalculatorTrainer class in the SolidExercices project and add the project SolidExercices.Console
  • Q4: what are the issues with this class?
• Make your Calculator implementation able to give a result for these operations (for impossible cases, return a standard ArgumentException with an explicit message => caught by CalculatorTrainer)
  • Don't forget tests!
• Extract operations in a class
  • Q5: what is the principle you are applying in this case?
• Make the trainer independent from this class with an abstraction + extract instanciation of any classes out of the trainer class
  • Q6: what is the principle you are applying in this case?
• Now we would like to access a list of operations from a link (URL) => implement the previous abstraction to access this URL
  • Format returned by the URL will be JSON, i.e [ {operation: ""}, { ...}, ...]
  • Adapt the console application to take URL as first parameter, and when URL given, use it to retrieve operations
• For now, trainer is just a command line, create a Web API to expose the following contract:
  • POST /calculate { operation: "...an operation..." }
  • POST /train { from: "...some URL..."}