to_d to always return 2 decimals places in ruby

问题:

I'm dealing with currencies and I want to round down the number to 2 decimal places. Even if the number is 500.0, I would like it to be 500.00 to be consistent. When I do "500.00".to_d it converts it to 500.0.

Whats a good way of changing this behavior? I also use this method to round down to 2 digits and make sure it always has 2 decimals.

def self.round_down(x, n=2)     s = x.to_s           l = s.index('.') ? s.index('.') + 1 + n : s.length     s = s[0, l]     s =  s.index('.') ? s.length - (s.index('.') + 1) == 1 ? s 

回答1:

In addition to mcfinnigan's answer, you can also use the following to get 2 decimal places

'%.2f' % 500 # "500.00"

This use case is known as the string format operator

回答2:

Here's a hint. 500.00 is a representation of the number 500.0

Specifically, sprintf will help you:

irb(main):004:0> sprintf "%.2f", 500.0 => "500.00"

回答3:

Since you are using Rails and this seems to be related to a view, there's number_with_precision:

number_with_precision(500, precision: 2) #=> "500.00"  I18n.locale = :de number_with_precision(500, precision: 2) #=> "500,00"

For currencies I'd suggest number_to_currency:

number_to_currency(500) #=> "$500.00"

回答4:

Do not use floating point numbers to represent money. See this question for a good overview of why this is a bad idea.

Instead, store monetary values as integers (representing cents), or have a look at the money gem that provides lots of useful functionality for dealing with such values.

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