Learning Ruby, Looking for Possible Refactoring for If Statement

Question

I've got a few ideas but wanted to get a few other options. Here is the ugly:

def normal_balance
  if type.to_s == 'Asset' or type.to_s == 'Expense'
    if contra
      "Credit"
    else
      "Debit"
    end
  else
    if contra
      "Debit"
    else
      "Credit"
    end
  end
end

What type of value is type? (Why are you calling to_s on it?) — Phrogz
– Phrogz, Commented Apr 22, 2012 at 15:28

Niklas B. · Accepted Answer · 2012-04-22 15:34:02Z

2

Not exactly a ruby-specific method, but since you're just inverting a boolean if a value in a given set, you can represent the boolean as a variable and then just use one condition to obtainin the 'debit' or 'credit' string.

def normal_balance
  debit = %w[Asset Expense].include?(type.to_s) ? !contra : contra
  debit ? "Debit" : "Credit"
end

edited Apr 22, 2012 at 15:34

Niklas B.

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answered Apr 22, 2012 at 15:03

d11wtq

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2 Comments

Matt Walston Over a year ago

Thanks. Big thing I've taken away here is the ? operator. I remember reading about it but application didn't come to mind.

Matt Walston Over a year ago

Yeah, it is a discriminator due to the model using datamapper.

Niklas B. · Accepted Answer · 2012-04-22 15:31:13Z

1

%w[Asset Expense].include?(type.to_s) == !!contra ? "Credit" : "Debit"

The !! is just there to force contra into a boolean, so we can compare it using ==. It could also be written as

%w[Asset Expense].include?(type.to_s) ^ contra ? "Debit" : "Credit"

But that's less readable, IMHO.

edited Apr 22, 2012 at 15:31

answered Apr 22, 2012 at 15:24

Niklas B.

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4 Comments

Matt Walston Over a year ago

Thanks. Certainly most concise. Took some reading to refresh my self on a few of the operators.

Andrew Marshall Over a year ago

Isn't ^ going to return the opposite of ==? It's XOR, so true ^ true == false whereas (true == true) == true. Perhaps you meant &?

Niklas B. Over a year ago

@Andrew: That's why I swapped the strings. Boolean a ^ b is equivalent to !!a != !!b. & has different semantics, by the way.

Andrew Marshall Over a year ago

@NiklasB. Ahhhh did not see that, my fault.

SwiftMango · Accepted Answer · 2012-04-22 15:31:46Z

0

def normal_balance(type,con)
  contra = {:yes => 'Debit'}
  contra.default= 'Credit'
  card_type = {:Asset => contra, :Expense => contra}
  card_type.default = contra

  card_type[type.to_sym][con.to_sym]
end

This is mostly used for replacing if that you use a hash.

I don't know what is the possible value for contra so you should replace that in the first hash.

Actually in your case you only test for contra_type. Maybe you should test that only.

edited Apr 22, 2012 at 15:31

answered Apr 22, 2012 at 15:18

SwiftMango

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1 Comment

Matt Walston Over a year ago

Thanks. I see that now on the original IF statement

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