to_d 总是在 ruby 中返回 2 个小数位
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to_d to always return 2 decimals places in ruby
提问by ed1t
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.
我正在处理货币，我想将数字四舍五入到小数点后两位。即使数字是 500.0，我也希望它是 500.00 以保持一致。当我执行 "500.00".to_d 时，它会将其转换为 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.
什么是改变这种行为的好方法？我也使用这种方法向下舍入到 2 位数字，并确保它始终有 2 位小数。
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 << '0' : s : s << '.00'
s.to_f
end
回答by jvnill
In addition to mcfinnigan's answer, you can also use the following to get 2 decimal places
除了 mcfinnigan 的答案，您还可以使用以下方法获得 2 位小数
'%.2f' % 500 # "500.00"
This use case is known as the string format operator
此用例称为字符串格式运算符
回答by Stefan
Since you are using Rails and this seems to be related to a view, there's number_with_precision:
由于您使用的是 Rails 并且这似乎与视图有关，因此有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:
对于货币，我建议number_to_currency：
number_to_currency(500)
#=> "0.00"
回答by mcfinnigan
Here's a hint. 500.00 is a representation of the number 500.0
这是一个提示。500.00 是数字 500.0 的表示
Specifically, sprintf will help you:
具体来说，sprintf 将帮助您：
irb(main):004:0> sprintf "%.2f", 500.0
=> "500.00"
回答by Lars Haugseth
Do not use floating point numbers to represent money. See this questionfor a good overview of why this is a bad idea.
不要使用浮点数来表示金钱。请参阅此问题以很好地概述为什么这是一个坏主意。
Instead, store monetary values as integers (representing cents), or have a look at the moneygem that provides lots of useful functionality for dealing with such values.
相反，将货币值存储为整数（代表美分），或者查看提供许多有用功能来处理此类值的货币宝石。
回答by webaholik
There was a requirement to round DOWN.
需要四舍五入。
Most other answers round 500.016 UP to 500.02
大多数其他答案将 500.016 UP 到 500.02
Try:
尝试：
def self.round_down(x, n = 2)
"%.#{n}f" % x.to_d.truncate(n)
end
irb(main):024:0> x=500.0; '%.2f' % x.to_d.truncate(2)
=> "500.00"
irb(main):025:0> x=500.016; '%.2f' % x.to_d.truncate(2)
=> "500.01"
