{"id":1900,"date":"2020-09-16T10:36:34","date_gmt":"2020-09-16T08:36:34","guid":{"rendered":"http:\/\/web.evertop.pl\/understanding-solid-principles-interface-segregation\/"},"modified":"2021-06-17T12:51:28","modified_gmt":"2021-06-17T10:51:28","slug":"understanding-solid-principles-interface-segregation","status":"publish","type":"post","link":"https:\/\/www.evertop.pl\/en\/understanding-solid-principles-interface-segregation\/","title":{"rendered":"SOLID: Interface Segregation Principle (ISP)"},"content":{"rendered":"

Have you ever seen a class method in your project, the core of which would be one line only: throw new NotImplementedException()?
\nIs this the right solution? Could such a code cause an issue?<\/p>\n

Not Implemented Exception<\/h3>\n

Amongst all the rules SOLID ISP is the easiest one. However, even that rule is often being infringed. The above method helps to create good interfaces. This means \u2013 interfaces which define the contract to so many coherent functions that there is no chance the class occurs, which implements only part of the contract. Let\u2019s take a look at a simple example of the interface for geometric figures.<\/p>\n

\"class<\/p>\n

Does the Circle need to have the HowManySides method?NoImplementedException?
\nSuch a solution is always incorrect. The above exception should only suggest that there is still a method to be implemented. It is not to indicate that a specific object doesn\u2019t have the functionality described by the interface. In this simple example the setup of the interfaces is presented in the picture below:<\/p>\n

\"class<\/p>\n

When creating the interfaces we should always consider them to be a certain definition of functionality, which will be provided by the implementing classes. This functionality (the only one), according to SRP, can be divided into several public methods. However, they should define one fixed indivisible combination. ICollection<T> from the .NET environment is a good example here, it has \u2018111\u2019 methods. It classifies the object as a collection providing it fulfills certain rules:<\/p>\n