[ruby] Find value in an array

In Ruby, how can I find a value in an array?

If you want find one value from array, use Array#find:

arr = [1,2,6,4,9] 
arr.find {|e| e % 3 == 0}   #=>  6

See also:

arr.select {|e| e % 3 == 0} #=> [ 6, 9 ]
e.include? 6              #=> true

To find if a value exists in an Array you can also use #in? when using ActiveSupport. #in? works for any object that responds to #include?:

arr = [1, 6]
6.in? arr                 #=> true

You can go for array methods.

To see all array methods use methods function with array. For Example,

a = ["name", "surname"] 
a.methods

By the way you can use different method for checking value in array You can use a.include?("name").

Like this?

a = [ "a", "b", "c", "d", "e" ]
a[2] +  a[0] + a[1]    #=> "cab"
a[6]                   #=> nil
a[1, 2]                #=> [ "b", "c" ]
a[1..3]                #=> [ "b", "c", "d" ]
a[4..7]                #=> [ "e" ]
a[6..10]               #=> nil
a[-3, 3]               #=> [ "c", "d", "e" ]
# special cases
a[5]                   #=> nil
a[5, 1]                #=> []
a[5..10]               #=> []

or like this?

a = [ "a", "b", "c" ]
a.index("b")   #=> 1
a.index("z")   #=> nil

See the manual.

This answer is for everyone that realizes the accepted answer does not address the question as it currently written.

The question asks how to find a value in an array. The accepted answer shows how to check whether a value exists in an array.

There is already an example using index, so I am providing an example using the select method.

1.9.3-p327 :012 > x = [1,2,3,4,5]
  => [1, 2, 3, 4, 5] 
1.9.3-p327 :013 > x.select {|y| y == 1}
  => [1]

Using Array#select will give you an array of elements that meet the criteria. But if you're looking for a way of getting the element out of the array that meets your criteria, Enumerable#detect would be a better way to go:

array = [1,2,3]
found = array.select {|e| e == 3} #=> [3]
found = array.detect {|e| e == 3} #=> 3

Otherwise you'd have to do something awkward like:

found = array.select {|e| e == 3}.first

you can use Array.select or Array.index to do that.

I know this question has already been answered, but I came here looking for a way to filter elements in an Array based on some criteria. So here is my solution example: using select, I find all constants in Class that start with "RUBY_"

Class.constants.select {|c| c.to_s =~ /^RUBY_/ }

UPDATE: In the meantime I have discovered that Array#grep works much better. For the above example,

Class.constants.grep /^RUBY_/

did the trick.

Use:

myarray.index "valuetoFind"

That will return you the index of the element you want or nil if your array doesn't contain the value.

Thanks for replies.

I did like this:

puts 'find' if array.include?(value)