Convert String to Decimal Number in Ruby

Convert string to decimal number in ruby

You call to_i, you get integer.

Try calling to_f, you should get a float.

For more string conversion methods, look here.

Ruby convert 2 decimal string into a number and keep the two decimals

Float

You can convert "5565.80" to a float :

value = "5565.80".to_f
# 5565.8

And then display the value with two decimals :

'%.2f' % value
# "5565.80"

A float has double-precision in Ruby, so your value will actually be :

5565.800000000000181898940354...

As a float, you cannot save exactly 5565.80.

Exact values

Integer

If you want exact values (e.g. for currency), you could use integers for cents :

"5565.80".delete('.').to_i
# 556580

When you need the corresponding float, you could divide it by 100.0.

Decimal

If you're working with a database, you could use decimal(20,2) or something equivalent.

BigDecimal

You could also use BigDecimal :

require 'bigdecimal'
BigDecimal.new("5565.80")

It will save the exact value but will be much slower than int or float.

Ruby Convert String to Decimal

It's maybe not the best way to do it but here is something that works :

"$ 10.80".match(/[0-9|\.]+/)[0].to_f

Ruby on Rails Migration Convert From String To Decimal

What you do is an atomic operation, where first delete the column that you will not use. Then create the column of type decimal. Finally update the table and assign values. If you do not want to lose the information then you should support it through a SQL update procedure converting types. I hope you have served as an orientation. Greetings.

Lo que debes hacer es una operación atómica, donde primero elimines la columna que no vas a utilizar. Luego crear la columna de tipo decimal. Por último actualizar la tabla y asignarle valores. En caso de que no quieras perder la información deberías respaldarla para luego a través de un procedimiento SQL actualicen convirtiendo los tipos. Espero que te haya servido como una orientación. Saludos.

class ChangeOddsAndUnitsColumn < ActiveRecord::Migration
  def up
    change_table :bets do |t|
      t.decimal :units_placed, precision: 16, scale: 2
    end
    Bets.update_all ["units_placed = ?", 0.0]
  end

  def down
    remove_column :bets, :units_placed
  end
end

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.

How to convert a scientific notation string to decimal notation?

Just use string conversion. The necessary coercion to float will be done automatically:

"%f" % "1.0e-05"
=> "0.000010"

# Which, behind the scenes is the same as:
"%f" % "1.0e-05".to_f
=> "0.000010"

Adjust as necessary to get more or less accuracy. For example:

"%.5f" % "1.0e-05"
=> "0.00001"

If you want to get real fancy and chop off unnecessary zeros at the end, here's one way. (Hopefully someone will suggest something more elegant; I couldn't think of anything):

("%.20f" % "1.0e-05").sub(/\.?0*$/, "")
=> "0.00001"

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