How to sum array of numbers in Ruby?

I have an array of integers.

For example:

array = [123,321,12389]

Is there any nice way to get the sum of them?

I know, that

sum = 0
array.each { |a| sum+=a }


would work.

Alternatively (just for comparison), if you have Rails installed (actually just ActiveSupport):

require 'activesupport'
array.sum

ruby 1.8.7 way is the following:

array.inject(0, &:+)

Also allows for `[1,2].sum{|x| x * 2 } == 6`:

#

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class Array
def sum(method = nil, &block)
if block_given?
raise ArgumentError, "You cannot pass a block and a method!" if method
inject(0) { |sum, i| sum + yield(i) }
elsif method
inject(0) { |sum, i| sum + i.send(method) }
else
inject(0) { |sum, i| sum + i }
end
end
end

Just for the sake of diversity, you can also do this if your array is not an array of numbers, but rather an array of objects that have properties that are numbers (e.g. amount):

array.inject(0){|sum,x| sum + x.amount}

You can also do it in easy way

def sum(numbers)
return 0 if numbers.length < 1
result = 0
numbers.each { |num| result += num }
result
end

You can use *.map* and *.sum* like:

array.map { |e| e }.sum

array.reduce(0, :+)

While equivalent to `array.inject(0, :+)`, the term **reduce** is entering a more common vernacular with the rise of [MapReduce programming models][1].

**inject**, **reduce**, **fold**, **accumulate**, and **compress** are all synonymous as a class of [folding functions][2]. I find consistency across your code base most important, but since various communities tend to prefer one word over another, it’s nonetheless useful to know the alternatives.

To emphasize the map-reduce verbiage, here’s a version that is a little bit more forgiving on what ends up in that array.

array.map(&:to_i).reduce(0, :+)

Some additional relevant reading:

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[1]:

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[2]:

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Ruby 2.4.0 is released, and it has an [Enumerable#sum][1] method. So you can do

array.sum

Examples from the docs:

{ 1 => 10, 2 => 20 }.sum {|k, v| k * v } #=> 50
(1..10).sum #=> 55
(1..10).sum {|v| v * 2 } #=> 110


[1]:

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# New for Ruby 2.4.0

You can use the aptly named method `Enumerable#sum`. It has a lot of advantages over `inject(:+)` but there are some important notes to read at the end as well.

## Examples

### Ranges

(1..100).sum
#=> 5050

### Arrays

[1, 2, 4, 9, 2, 3].sum
#=> 21

[1.9, 6.3, 20.3, 49.2].sum
#=> 77.7

## Important note
This method is not equivalent to `#inject(:+)`. For example

%w(a b c).inject(:+)
#=> "abc"
%w(a b c).sum
#=> TypeError: String can't be coerced into Integer

Also,


(1..1000000000).sum
#=> 500000000500000000 (execution time: less than 1s)
(1..1000000000).inject(:+)
#=> 500000000500000000 (execution time: upwards of a minute)

See [this answer](

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) for more information on why `sum` is like this.