Rails Convert String to Number

Strictly convert string to integer (or nil)

Use Integer(string)

It will raise an ArgumentError error if the string cannot convert to an integer.

Integer('5abc') #=> ArgumentError: invalid value for Integer(): "5abc"
Integer('5') #=> 5

You'd still need your number_or_nil method if you want the behavior to be that nil is returned when a string cannot be converted.

def number_or_nil(string)
  Integer(string || '')
rescue ArgumentError
  nil
end

You should be careful to rescue from a particular exception. A bare rescue (such as "rescue nil") will rescue from any error which inherits from StandardError and may interfere with the execution of your program in ways you don't expect. Integer() will raise an ArgumentError, so specify that.

If you'd rather not deal with exceptions and just prefer a shorter version of your number_or_nil you can take advantage of implicit return values and write it as:

def number_or_nil(string)
  num = string.to_i
  num if num.to_s == string
end

number_or_nil '5' #=> 5
number_or_nil '5abc' #=> nil

This will work the way you expect.

rails convert string to number

.to_f is the right way.

Example:

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?

Added:

If you know that 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.

If you're not sure of the string's content, then using .to_f will 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

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_f behavior may be just what you want, it depends on your problem case.

Depending on what you want to do in various error cases, you can use Kernel::Float as Mark Rushakoff suggests, since it raises an error when it is not perfectly happy with converting the input string.

convert string number with bytes to integer in rails (32MB - 32.megabytes)

There's filesize

It's quite trivial to write your own:
But you can write your own:

def convert_size_to_bytes
  md = match(/^(?<num>\d+)\s?(?<unit>\w+)?$/)
  md[:num].to_i * 
      case md[:unit]
      when 'KB'
        1024
      when 'MB'
        1024**2
      when 'GB'
        1024**3
      when 'TB'
        1024**4
      when 'PB'
        1024**5
      when 'EB'
        1024**6
      when 'ZB'
        1024**7
      when 'YB'
        1024**8
      else
        1
      end
    end

Convert string to number in where clause

ActiveRecord where accepts string as query constructor

OnlineCourseRegistration.where("course_class_id = ? AND status = ? AND score > ?", 681, "Completed", 70).last

Convert field from integer to string in one rails Active Record relation before sending json

All Rails models have an as_json method that gets called when rednering the model to JSON. You can override this method within your models to set up custom JSON formatting. In your case, you may want to add something like this to your Wine model:

def as_json(opts = {})
  json = super(opts)
  json["grape_id"] = self.grape_id.to_s
  json
end

The method gives you the default model JSON when you call the super method and set it to the json variable, then stringifies grape_id and sets it in the JSON, and finally returns the updated JSON.

Now, any time a controller returns a JSON version of single Wine model, or an association of multiple Wine models, the JSON will be formatted through this updated method and the grape_id will be stringified every time.

Convert array of strings to an array of integers

To convert a string to number you have the to_i method.

To convert an array of strings you need to go through the array items and apply to_i on them. You can achieve that with map or map! methods:

> ["", "22", "14", "18"].map(&:to_i)
# Result: [0, 22, 14, 18]

Since don't want the 0 - just as @Sebastian Palma said in the comment, you will need to use an extra operation to remove the empty strings: (The following is his answer! Vote for his comment instead :D)

> ["", "22", "14", "18"].reject(&:empty?).map(&:to_i)
# Result: [22, 14, 18]

the difference between map and map! is that map will return a new array, while map! will change the original array.

Convert string to int array in Ruby

A simple one liner would be:

s.each_char.map(&:to_i)
#=> [2, 3, 5, 3, 4]

If you want it to be error explicit if the string is not contained of just integers, you could do:

s.each_char.map { |c| Integer(c) }

This would raise an ArgumentError: invalid value for Integer(): if your string contained something else than integers. Otherwise for .to_i you would see zeros for characters.

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