[Ruby] Extract only the elements that match the conditions and create a new array. filter and select
This is a personal memo.
There are select and filter as methods to extract only the elements that match the conditions and create a new array.
This is the same for both. Looking at the official page of ruby, select is used in the example of the filter method.
## range object For range objects from 1 to 3, only the numerical values ​​corresponding to 2 or less are extracted and an array is created.
select
range = 1..3 #[1,2,3]
range2 = range.select{|x| x<=2}
p range2
#output
[1, 2]
filter
range = 1..3 #[1,2,3]
range2 = range.filter{|x| x<=2}
p range2
#output
[1, 2]
The result is the same for both filter and select.
## Array
select
arr = [1,2,3]
arr2 = arr.select{|x| x<=2}
p arr2
#output
[1, 2]
## object For objects, set two variables. The first variable is the key and the second variable is the value.
- If there is only one variable, a KV pair will be entered.
python
obj = {:a=>1, :b=>2, :c=>3}
obj2 = obj.select{|x, y| y<=2}
p obj2
#output
{:a=>1, :b=>2}
Unlike the map method, the processing result is returned as an object. (In the case of map, an array is returned)