如何正确定义要创建的不同对象的数量？

Question

I have this class with these two methods and a list:

public class Example
{
    protected List<Person> ExampleList = new List<Person>();

    public Example()
    {
        CreatePersonInstances();

        foreach (Person personToInitialize in ExampleList)
            personToInitialize.Initialize();
    }

    protected void CreatePersonInstances()
    {
        ExampleList.Add(new Employee());
        ExampleList.Add(new Manager());
        ExampleList.Add(new Recruiter());                                                                            
    }
}

How can I create properly a specific number of items from a user defined quantity?

For example, if the user decides to create two employees, a manager and zero recruiters, I have to be able to create the defined quantity of objects in CreatePersonInstaces();

Answer 1

You could begin by adding 3 parameters in the constructor, - a parameter each signifying number of Employee/Manager/Recruiter to create.

public Example(int employee,int manager,int Recruiter)
{
   // Rest of code
}

You could also make your CreatePersonInstances method generic that accepts a parameter type which inherits from Person along with number of instances to create.

protected void CreatePersonInstances<T>(int count) where T:Person,new()
{
    EmployeeList.AddRange(IEnumerable.Range(1,count).Select(x=>new T()));
}

You could now change your constructor definition as

public Example(int employeeCount,int managerCount,int recruiterCount)
{
    CreatePersonInstances<Employee>(employeeCount);
    CreatePersonInstances<Manager>(managerCount);
    CreatePersonInstances<Recruiter>(recruiterCount);
    
    foreach (Person personToInitialize in ExampleList)
            personToInitialize.Initialize();
}

Answer 2

    protected void CreatePersonInstances(int employeeCount, int managerCount, int recruiterCount)
    {
        //some validation to check count number not negative

        ExampleList.AddRange(Enumerable.Range(0, employeeCount).Select(x => new Employee()));
        ExampleList.AddRange(Enumerable.Range(0, managerCount).Select(x => new Manager()));
        ExampleList.AddRange(Enumerable.Range(0, recruiterCount).Select(x => new Recruiter()));
    }

where Employee, Manager and recruiter inherit from Person entity

    public class Person
    {
        public string Name { get; set; }
    }

    public class Employee : Person
    {
        public int EmployeeId { get; set; }
    }

    public class Manager : Person
    {
        public int ManagerId { get; set; }
    }

    public class Recruiter : Person
    {
        public int RecruiterId { get; set; }
    }

Besides the scope of the question, this whole model is a good use case for the Factory Design Pattern. If you havent, check it out 👍