Several of the standard array methods modify the array itself rather than returning a modified copy of the array.
These methods are marked with a terminating exclamation point, such as sort!, reverse!, flatten!, and compact!.
The << method modifies the array to its left by adding to it the array on its right.
clear method removes all the elements from the given array.
delete and delete_at remove selected elements.
The following table shows some of the more commonly used Array methods.
|&||Returns common elements of two arrays, no duplicates|
|+||Returns array concatenating two arrays|
|-||Returns array with items in second array removed from first|
|<<||Modifies first array by appending items from second array|
|clear||Modifies array by removing all elements|
|compact||Returns array with nil items removed|
|compact!||Modifies array by removing nil items|
|delete( object )||Modifies array by deleting object|
|delete_at( index )||Modifies array by deleting item at index|
|flatten||Unpacks nested array items and returns array|
|flatten!||Modifies array by unpacking nested array items|
|length||Returns number of elements in array|
|reverse||Returns array with elements in reverse order|
|reverse!||Modifies array by reversing element order|
|sort||Returns array sorted using <=>|
|sort!||Modifies array sorted using <=>|
arr1 = [1,1,2,2,3,3] arr2 = [1,2,3,4,5,6,7,8,9] # from ww w. j a v a 2 s . com arr3 = ['h','e','l','l','o',' ',nil,'w','o','r','l','d'] p(arr1&arr2 ) #=> [1, 2, 3] p(arr1+arr2) #=> [1, 1, 2, 2, 3, 3, 1, 2, 3, 4, 5, 6, 7, 8, 9] p(arr1-arr2) #=>  p(arr2-arr1) #=> [4, 5, 6, 7, 8, 9] arr1<<arr2 p(arr1) #=> [1, 1, 2, 2, 3, 3, [1, 2, 3, 4, 5, 6, 7, 8, 9]] arr1.clear p(arr1) #=>
An array is flattened when it contains no subarrays.
So if you have an array like [1,[2,3]], you can call [1,[2,3]].flatten to return this array: [1,2,3].
An array is said to be compacted when it contains no nil items.
So if you have an array like [1,2,nil,3], you can call [1,2,nil,3].compact to return this array: [1,2,3].
The methods of Array can be chained together by placing one method call directly after the other:
p( [1,nil,[2,nil,3]].flatten.compact ) #=> [1,2,3]