There are many methods for manipulating the elements of ruby's array. After all, I tried to compare which one behaves and which one is the most efficient.
| Method | Return value | behavior |
|---|---|---|
| each | Array of receivers | Iterate over the elements of the array one by one in the block |
| each_slice | nil | Iterate over multiple units of array elements in a block |
| each_with_index | Array of receivers | Iterate over array elements and index numbers within a block |
| map | Changed array | Change elements as they are in an array |
| select | Changed array | Keep the array and narrow down the elements for which the conditional expression is true |
| reject | Changed array | Keep the array and narrow down to the elements whose conditional expression is false |
| find | element | elementの中で、最初にヒットしたelementを取り出す |
each Loop the element in the singular
array = ["Apple", "Orange", "watermelon", "melon"]
array.each do |obj|
p obj
end
Return value
Apple
Orange
watermelon
melon
=> ["Apple", "Orange", "watermelon", "melon"]
each_slice Loop multiple elements
array.each_slice(2) do |a|
p a
p a
end
Return value
["Apple", "Orange"]
["watermelon", "melon"]
=> nil
each_with_index You can retrieve the index along with the element
array.each_with_index do |obj,index|
p obj
p index
end
Return value
"Apple"
0
"Orange"
1
"watermelon"
2
"melon"
3
=> ["Apple", "Orange", "watermelon", "melon"]
map Tweak the elements and return as an array
array = [1, 2, 3, 4, 5]
array_new = array.map{ |i| i*2 }
Return value
[2, 4, 6, 8, 10]
select Returns an array with elements whose conditional expression return value is true
array = [1, 2, 3, 4, 5]
array_new = array.select{ |i| i > 3 }
Return value
[4, 5]
reject Returns an array with an element whose conditional expression return value is false
array = [1, 2, 3, 4, 5]
array_new = array.reject{ |i| i % 2 == 0 }
Return value
[1, 3, 5]
find Find and retrieve the first element that is true in the conditional expression
array = [1, 2, 3, 4, 5]
array_new = array.find{ |i| i > 3 }
Return value
4
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