pg 81 why is there 2 constructors with paramaters flipped?

mikezx10 · February 11th, 2012, 09:44 AM

public ApplicationBankAccountService(
IBankAccountRepository bankRepository,
BankAccountService bankAccountService)
{
_bankRepository = bankRepository;
_bankAccountService = bankAccountService;
}
public ApplicationBankAccountService(
BankAccountService bankAccountService,
IBankAccountRepository bankRepository)
{
_bankAccountService = bankAccountService;
_bankRepository = bankRepository;
}

irProject · February 12th, 2012, 03:31 PM

maybe because of flexibility and easy to use

mikezx10 · February 24th, 2012, 09:53 AM

the parameters are both of the same types making it no more flexible and more confusing.

irProject · February 25th, 2012, 01:40 AM

Hi there

imagine you are writing a function named Add that adds two float and int values. how do you write it?

float Add(float a, int b){

}

or maybe

float Add(int a, float b){

}

or maybe overloaded and coupled choice:

Code:

float Add(float a, int b){
 return a+b;
}

float Add(int a, float b){
 return a+b;
}

I think the complete choice is the best. so user is not limited to pass numbers in a special order.

float x = Add(2, 2.564);
float y = Add(345.9374, 17);

elbandit · February 25th, 2012, 05:49 AM

Hi guys, this is a typo I'm afraid - sorry.

Although you do touch on a topic that I will be covering in my new book. That of primitive obsession. Take this code...

Code:

decimal apply_vat(decimal price, decimal vat_rare)
{
     //logic ....
}

It would be easy to get the parameters confused when calling...

Code:

decimal price_after_vat = apply_vat(1.23, 199.99); // Whoops!

Better to use value types and make things explicit...

Code:

Money apply_vat(Money price, VatRate vat)
{
  .....
}

Or better still...

Code:

Public Class Money
{
     Money apply(VatRate vat)
     {
          // return new Money with vat applied
      }
}

This way you avoid confusion, you make the concepts of money and vat more explicit and you enable them to encapsulate behaviour.

Thoughts?

Cheers
Scott