Specification Pattern
It's a specification pattern that is used to encapsulate piece of domain knowledge into single unit. So that It's re-usable and easily testable.
https://www.nuget.org/packages/Develoopers.Spector
dotnet add package Develoopers.Spector --version 1.0.0Consider the following example:
public class User
{
public void User(string name, int age)
{
Name = name;
Age = age;
}
public string Name { get; set; }
public int Age { get; set; }
}
public class IsAdultUserSpec : ISpector<User>
{
public bool IsSatisfiedBy(User user) => user.Age >= 18;
}
public class IsValidUserSpec : ISpector<User>
{
public bool IsSatisfiedBy(User obj) => !string.IsNullOrEmpty(obj.Name);
}The usage is as following:
// Simple Usage
var user = new UserModel("John", 20);
var adultUserSpec = new IsAdultUserSpec();
adultUserSpec.IsSatisfiedBy(user)
// And Composition
var adultUserSpec = new IsAdultUserSpec();
var validUserSpec = new IsValidUserSpec();
var andCompositeSpec = isValidUserSpec.And(isAdultUserSpec);
// Or Composition
var adultUserSpec = new IsAdultUserSpec();
var validUserSpec = new IsValidUserSpec();
var orCompositeSpec = isValidUserSpec.Or(isAdultUserSpec);
// Not Composition
var adultUserSpec = new IsAdultUserSpec();
adultUserSpec.Not().IsSatisfiedBy(user)
// Generic Spec Usage
var adultUserSpec = new Spec<User>(x => x.Age >= 18);
adultUserSpec.IsSatisfiedBy(user);