Clean Code_Note6_Decrease the Number of Parameters

 
一個method若有太多參數通常容易讓人不好呼叫和使用,因此需要來減少傳入參數。

以下為參數過多的範例

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using System;
using System.Collections.Generic;
using System.IO;

namespace CleanUpMethods
{
    public class DecreaseNumberOfParameters
    {
        public DecreaseNumberOfParameters(string name, string homeAddress, string country, string email, string telephone, string fileLocation)
        {
            SaveHomeAddress(name, homeAddress, email, country, fileLocation, telephone);
        }

        public void SaveHomeAddress(string name, string homeAddress, string country, string email, string fileLocation, string telephone)
        {

            if (string.IsNullOrEmpty(name) || string.IsNullOrEmpty(homeAddress)
                || string.IsNullOrEmpty(fileLocation) || string.IsNullOrEmpty(telephone))
            {
                Console.WriteLine("Input parameters are empty");
            }
            else
            {
                using FileStream fileStream = new FileStream(fileLocation, FileMode.Append);
                using StreamWriter writer = new StreamWriter(fileStream);
                List<string> aPersonRecod = new List<string>
                {
                    name,
                    homeAddress,
                    country,
                    email,
                    telephone
                };
                writer.WriteLine(aPersonRecod);
            }
        }
    }
}


通常建議可以利用新建一個DTO Class (Data Transfer Object)
PersonRecord.cs



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using System;
using System.Collections.Generic;
using System.IO;

namespace CleanUpMethods
{
    public class PersonRecord
    {
        public string Name { get; set; }
        public string HomeAddress { get; set; }
        public string Country { get; set; }
        public string Email { get; set; }
        public string FileLocation { get; set; }
    }

    public class DecreaseNumberOfParameters
    {
        public DecreaseNumberOfParameters(string name, string homeAddress, string country, string email, string telephone, string fileLocation)
        {
            SaveHomeAddress(name, homeAddress, email, country, fileLocation, telephone);
        }

        public void SaveHomeAddress(string name, string homeAddress, string country, string email, string fileLocation, string telephone)
        {

            if (string.IsNullOrEmpty(name) || string.IsNullOrEmpty(homeAddress)
                || string.IsNullOrEmpty(fileLocation) || string.IsNullOrEmpty(telephone))
            {
                Console.WriteLine("Input parameters are empty");
            }
            else
            {
                using FileStream fileStream = new FileStream(fileLocation, FileMode.Append);
                using StreamWriter writer = new StreamWriter(fileStream);
                List<string> aPersonRecod = new List<string>
                {
                    name,
                    homeAddress,
                    country,
                    email,
                    telephone
                };
                writer.WriteLine(aPersonRecod);
            }
        }
    }
}







參數經過化簡為傳入一個物件後就比較容易維護了

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using System;
using System.Collections.Generic;
using System.IO;

namespace CleanUpMethods
{
    public class PersonRecord
    {
        public string Name { get; set; }
        public string HomeAddress { get; set; }
        public string Country { get; set; }
        public string Email { get; set; }
        public string FileLocation { get; set; }
    }

    public class DecreaseNumberOfParameters
    {
        public DecreaseNumberOfParameters(string name, string homeAddress, string country, string email, string telephone, string fileLocation)
        {
            PersonRecord personRecord = new PersonRecord
            {
                Name = name,
                HomeAddress = homeAddress,
                Email = email,
                Country = country,
                FileLocation = fileLocation
            };
            SaveHomeAddress(telephone, personRecord);
        }

        public void SaveHomeAddress(string telephone, PersonRecord personRecord)
        {

            if (string.IsNullOrEmpty(personRecord.Name) || string.IsNullOrEmpty(personRecord.HomeAddress)
                || string.IsNullOrEmpty(personRecord.FileLocation) || string.IsNullOrEmpty(telephone))
            {
                Console.WriteLine("Input parameters are empty");
            }
            else
            {
                using FileStream fileStream = new FileStream(personRecord.FileLocation, FileMode.Append);
                using StreamWriter writer = new StreamWriter(fileStream);
                List<string> aPersonRecod = new List<string>
                {
                    personRecord.Name,
                    personRecord.HomeAddress,
                    personRecord.Country,
                    personRecord.Email,
                    telephone
                };
                writer.WriteLine(aPersonRecod);
            }
        }
    }
}


另外還有一種情況是一個object能傳到底就傳到底
不要中途又變成很多參數傳入
一個實際案例RegisterUser方法傳入的是一個UserModel納在當中又有去呼叫到
AuthService物件中的CreateUser這裡其實就是可以直接改為model傳入的部分
不需要用這麼多參數分開

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using System;

namespace CleanUpMethods
{
    public class PreserveWholeObject
    {
        public interface Database
        {
            void SaveUser(string userName, string password, string email);
        }

        public class UserModel
        {
            public string UserName { get; set; }
            public string Email { get; set; }
            public string Password { get; set; }
            public string ConfirmPassword { get; set; }
        }

        public class User
        {
            public string UserName { get; set; }
            public string Email { get; set; }
        }

        public class AuthService
        {
            private static Database _database;

            public static User CreateUser(string userName, string password, string email)
            {
                _database.SaveUser(userName, password, email);
                return new User { Email = email, UserName = password };
            }
        }

        public User RegisterUser(UserModel model)
        {
            User newUser = null;

            try
            {
                newUser = AuthService.CreateUser(model.UserName, model.Password, model.Email);
            }
            catch(InsufficientMemoryException)
            {
                throw;
            }
            catch(Exception ex)
            {
                LogError(ex);
            }
            return newUser;
        }

        #region Other methods
        private void LogError(Exception ex)
        {
            throw new NotImplementedException();
        }
        #endregion
    }
}








經調整後最終一個程式

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using System;

namespace CleanUpMethods
{
    public class PreserveWholeObject
    {
        public interface Database
        {
            void SaveUser(string userName, string password, string email);
        }

        public class UserModel
        {
            public string UserName { get; set; }
            public string Email { get; set; }
            public string Password { get; set; }
            public string ConfirmPassword { get; set; }
        }

        public class User
        {
            public string UserName { get; set; }
            public string Email { get; set; }
        }

        public class AuthService
        {
            private static Database _database;

            public static User CreateUser(UserModel model)
            {
                _database.SaveUser(model.UserName, model.Password, model.Email);
                return new User { Email = model.Email, UserName = model.UserName };
            }
        }

        public User RegisterUser(UserModel model)
        {
            User newUser = null;

            try
            {
                newUser = AuthService.CreateUser(model);
            }
            catch(InsufficientMemoryException)
            {
                throw;
            }
            catch(Exception ex)
            {
                LogError(ex);
            }
            return newUser;
        }

        #region Other methods
        private void LogError(Exception ex)
        {
            throw new NotImplementedException();
        }
        #endregion
    }
}


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