Ruby - Convert Integer to String

`to_s` isn't converting an integer to a string

When you call puts on an array, it outputs each element of the array separately with a newline after each element. To confirm that your to_s methods are converting the number to a string, try using print instead of puts.

As for the nil that's output, that is the return value of your function. Unless there is an explicit return, the return value of a function will be the evaluation of the last line, which in your case is: puts number. The return value of puts number is nil; printing the value of number is a side effect, not the return value.

I'm curious as to why the output was indeed an array in your first lines of code (not within the function):

$  num = 233
$  number = num.to_s.split(//)
$  puts number
=> ['2', '3', '3']

I suspect that you actually saw that output after the num.to_s.split(//) line, not the puts number line.

Ruby - Convert Integer to String

Or you can convert the integer to its character value:

a[0].chr

How can I convert a string into an integer in RUBY?

To convert string to integer: my_str.to_i, for example

"foo".to_i       # 0
"132".to_i       # 132
"132.4".to_i     # 132
"foo132".to_i    # 0
"132foo".to_i    # 132

To find if a string has an odd or even number of characters: my_str.length.odd? or my_str.length.even?, for example:

"foo".length.odd?    # true
"132".length.odd?    # true
"foo".length.even?   # false
"132".length.even?   # false

SEE ALSO:

to_i

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.

Format integer to string with fixed length in Ruby

How about getting the last three digits using % 1000 instead of doing string manipulations?

[1, 12, 123, 1234].map { |e| format('%03d', e % 1000) }

Update:

As suggested by the Tin Man in the comments, the original version is better in terms of readability and only abount 1.05x slower than this one, so in most cases it probably makes sense to use that.

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.

In Ruby, why do I need to convert an integer into a string to print it?

print and puts do not require you to convert a number to a string. In this case, the problem is that you're trying to add a number to a string. This expression:

'I think you really mean ' + newnumber + ' right?'

has to be evaluated before puts can receive its argument. You can't add numbers to strings, for the reason stated in the error you'll get when you try:

TypeError: no implicit conversion of Fixnum into String

You can do this, though:

puts newnumber

If you want to get implicit type conversion while outputting, use interpolation:

puts "I think you really mean #{newnumber} right?"

Ruby will call to_s on newnumber automatically.

Note that you must use " double-quotes " around your string, because interpolation won't occur in single-quoted strings.

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