如何使用#{variable} 在 Ruby 中格式化带有浮点数的字符串？
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How to format a string with floats in Ruby using #{variable}?
提问by marcotama
I would like to format a string containing float variables including them with a fixed amount of decimals, and I would like to do it with this kind of formatting syntax:
我想格式化一个包含浮点变量的字符串，其中包括固定数量的小数，我想用这种格式语法来做：
amount = Math::PI
puts "Current amount: #{amount}"
and I would like to obtain Current amount: 3.14.
我想获得Current amount: 3.14.
I know I can do it with
我知道我可以做到
amount = Math::PI
puts "Current amount %.2f" % [amount]
but I am asking if it is possible to do it in the #{}way.
但我在问是否有可能以这种#{}方式做到这一点。
回答by Spajus
You can use "#{'%.2f' % var}":
您可以使用"#{'%.2f' % var}"：
irb(main):048:0> num = 3.1415
=> 3.1415
irb(main):049:0> "Pi is: #{'%.2f' % num}"
=> "Pi is: 3.14"
回答by Michael Kohl
You can do this, but I prefer the String#%version:
你可以这样做，但我更喜欢这个String#%版本：
puts "Current amount: #{format("%.2f", amount)}"
As @Bjoernsen pointed out, roundis the most straightforward approach and it also works with standard Ruby (1.9), not only Rails:
正如@Bjoernsen 指出的那样，round是最直接的方法，它也适用于标准 Ruby (1.9)，而不仅仅是 Rails：
http://www.ruby-doc.org/core-1.9.3/Float.html#method-i-round
http://www.ruby-doc.org/core-1.9.3/Float.html#method-i-round
回答by Lukas Stejskal
Yes, it's possible:
是的，这是可能的：
puts "Current amount: #{sprintf('%.2f', amount)}"
