Basic methods of Ruby arrays

I will make a note of the basic methods used in Ruby arrays.

version ruby 2.6.5p114

Add / remove to array

First, prepare an appropriate array

$ animals = ["dog", "cat", "rabbit"]
=> ["dog", "cat", "rabbit"]

• ** push ** Add element to the end of the array
• ** unshift ** Add element to the beginning of the array

$ animals.push('bear')
=> ["dog", "cat", "rabbit", "bear"]
$ animals.unshift('monkey')
=> ["monkey", "dog", "cat", "rabbit", "bear"]

• ** pop ** Delete one element from the end of the array
• ** shift ** Delete one element from the beginning of the array

$ animals
=> ["monkey", "dog", "cat", "rabbit", "bear"]
$ animals.pop
=> "bear"
$ animals.shift
=> "monkey"
$ animals
=> ["dog", "cat", "rabbit"]

Array formatting

• ** compact ** Delete only nil from the array

['dog',nil, 0, false,''].compact
=> ["dog", 0, false, ""]

• ** uniq ** Delete duplicate elements from the array

["dog", "cat", "rabbit", "dog"].uniq
=> ["dog", "cat", "rabbit"]

• ** flatten ** Returns a multidimensional array in one dimension

$ animals = ["dog", ["cat",["rabbit, bear"]]]
=> ["dog", ["cat", ["rabbit, bear"]]]
$ animals.flatten
=> ["dog", "cat", "rabbit, bear"]

• ** transpose ** Think of a two-dimensional array as a matrix and swap rows and columns

$ animals = [[1,2,3],["dog","cat","rabbit"]]
=> [[1, 2, 3], ["dog", "cat", "rabbit"]]
$ animals.transpose
=> [[1, "dog"], [2, "cat"], [3, "rabbit"]]

• ** zip ** Combine two arrays after swapping rows and columns

$ num = [1,2,3]
=> [1, 2, 3]
$ animals = ["dog","cat","rabbit"]
=> ["dog", "cat", "rabbit"]
$ num.zip(animals)
=> [[1, "dog"], [2, "cat"], [3, "rabbit"]]

Other useful methods

• ** size ** Returns the number of elements in the array

["dog", "cat", "rabbit"].size
=> 3

• ** sum ** Returns the value obtained by adding the elements of the array

[1,2,3].sum
=> 6

• ** sort ** Sort the elements of the array in order

[3,1,2].sort
=> [1, 2, 3]

• ** reverse ** Rearrange the elements of the array in reverse order

[1,2,3].reverse
=> [3, 2, 1]

• ** shuffle ** Randomly sort the elements of the array

[1,2,3].shuffle
=> [2, 1, 3]

• ** sample ** Get array elements randomly

[1,2,3].sample
=> 3
[1,2,3].sample
=> 1

• ** join ** Concatenate the character strings in the array

["dog", "cat", "rabbit"].join
=> "dogcatrabbit"
["dog", "cat", "rabbit"].join('When')
=> "dog, cat and rabbit"

• ** select ** Get the element that meets the conditions from the array and return it as a new array

num = [1,2,3,4,5,6]
=> [1, 2, 3, 4, 5, 6]
num.select {|n| n % 2 == 0}
=> [2, 4, 6]

• ** reject ** Deletes the elements that meet the conditions from the array and returns it as a new array

> num
=> [1, 2, 3, 4, 5, 6]
num.reject { |n| n % 2 == 0 }
=> [1, 3, 5]