Clean Code: Classes

• Class name should be noun, meaninful and in the title case with the first letter of each separate word capitalised.

class FileEntity {
}
class FileRepository {
}
class FileUploadService {
}
class FileResource {
}

• A class is a conceptual representation of entity in your application and contains only functions whatever entity needs to do.

class UserService {
    public UserEntity fetchUserByEmail(String Email) {
    }
    public List<UserEntity> fetchAllUsers() {
    }
    public List<UserEntity> fetchSubscribedUsers() {
    }
    
    public UserEntity updateUser(String id, UpdateUserRequest request) {
    }
   
    public UserEntity updateUserSubscription(String id, UpdateSubscriptionRequest request) {
    }
    public void deleteUserById(String id) {
    }
    public boolean isValidUser(String id) {
    }
    public boolean isSubscibedUser(String id) {
    }
    public void logoutUser(String id) {
    }
 }

• Define functions are tightly focused and do them well.
• It’s okay to have functions doing same thing but taking different parameters.

class UserService {
    public UserEntity fetchUsers() {
    }
    public List<UserEntity> fetchUsers(boolean isSubscribed) {
    }
    public List<UserEntity> fetchUsers(FilterUserRequest request){
    }
}

• Class should small and contains average of fewer than 30 functions and 600 lines of code [each function has 20 lines of code].
• Keep the utility methods and variables are private except some for testing.
• To write clean functions inside class, please check my previous post https://vignesh-satya.medium.com/clean-code-functions-f3cb17b691e2

I kept this story short on purpose, because I don’t want to explain it all in a story. I’ll see you in another story.