Ruby-on-rails rails 将字符串转换为数字
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rails convert string to number
提问by Yang
I am wondering what is a convenient function in Rails to convert a string with a negative sign into a number. e.g. -1005.32
我想知道 Rails 中有什么方便的函数可以将带有负号的字符串转换为数字。例如-1005.32
When I use the .to_fmethod, the number becomes 1005with the negative sign and decimal part being ignored.
当我使用该.to_f方法时，数字变为1005负号和小数部分被忽略。
回答by Larry K
.to_fis the right way.
.to_f是正确的方法。
Example:
例子：
irb(main):001:0> "-10".to_f
=> -10.0
irb(main):002:0> "-10.33".to_f
=> -10.33
Maybe your string does not include a regular "-" (dash)? Or is there a space between the dash and the first numeral?
也许您的字符串不包含常规的“-”（破折号）？还是破折号和第一个数字之间有空格？
Added:
添加：
If you knowthat your input string is a string version of a floating number, eg, "10.2", then .to_f is the best/simplest way to do the conversion.
如果您知道您的输入字符串是浮点数的字符串版本，例如“10.2”，那么 .to_f 是进行转换的最佳/最简单的方法。
If you're not sure of the string's content, then using .to_fwill give 0 in the case where you don't have any numbers in the string. It will give various other values depending on your input string too. Eg
如果您不确定字符串的内容，则.to_f在字符串中没有任何数字的情况下，使用将给出 0。它也会根据您的输入字符串提供各种其他值。例如
irb(main):001:0> "".to_f
=> 0.0
irb(main):002:0> "hi!".to_f
=> 0.0
irb(main):003:0> "4 you!".to_f
=> 4.0
The above .to_fbehavior may be just what you want, it depends on your problem case.
上述.to_f行为可能正是您想要的，这取决于您的问题案例。
Depending on what you want to do in various error cases, you can use Kernel::Floatas Mark Rushakoff suggests, since it raises an error when it is not perfectly happy with converting the input string.
根据您在各种错误情况下要执行的操作，您可以Kernel::Float按照 Mark Rushakoff 的建议使用，因为当它对转换输入字符串不满意时会引发错误。
回答by Mark Rushakoff
You should be using Kernel::Floatto convert the number; on invalid input, this will raise an error instead of just "trying" to convert it.
您应该使用Kernel::Float来转换数字；在无效输入上，这将引发错误，而不仅仅是“尝试”转换它。
>> "10.5".to_f
=> 10.5
>> "asdf".to_f # do you *really* want a zero for this?
=> 0.0
>> Float("asdf")
ArgumentError: invalid value for Float(): "asdf"
from (irb):11:in `Float'
from (irb):11
>> Float("10.5")
=> 10.5
