How can I delete some elements from an array and select them?
For example:
class Foo
def initialize
@a = [1,2,3,4,5,6,7,8,9]
end
def get_a
return @a
end
end
foo = Foo.new
b = foo.get_a.sth{ |e| e < 4 }
p b # => [1,2,3]
p foo.get_a # => [4,5,6,7,8,9,10]
What I can use instead of foo.get_a.sth?
If you don't need to retain the object id of a:
a = [1,2,3,4,5,6,7,8,9,10]
b, a = a.partition{|e| e < 4}
b # => [1, 2, 3]
a # => [4, 5, 6, 7, 8, 9, 10]
If you do need to retain the object id of a, then use a temporal array c:
a = [1,2,3,4,5,6,7,8,9,10]
b, c = a.partition{|e| e < 4}
a.replace(c)
a. a is result of a some_object.get_some_array function
a.select { |e| e < 4 } in that case? This will return the elements that pass the test.some_object.set_some_array c instead of a.replace c.Rails 6 now has this:
a = [1, 2, 3]
#=> [1, 2, 3]
a.extract! { |n| n.even? }
#=> [2]
a
#=> [1, 3]
If you were only deleting one item, this doesn't require duplicating the array, etc:
array = [{ id: 1 }, { id: 2 }, {id: 3 }]
array.delete_at(array.find_index { |element| element[:id] == 1 })
#=> {:id=>1}
a = [1, 2, 3, 4]
a.dup - (a.delete_if(&:even?))
#=> [2, 4]
a
#=> [1, 3]
a = [1, 2, 3, 4]
b = a.dup - (a.delete_if { |e| e < 4 })
a
#=> [4]
b
#=> [1, 2, 3]
Edit: It sounds like you are just after #select...
a = [1, 2, 3, 4]
a.select { |e| e < 3 }
#=> [1, 2]
I still don't believe ruby doesn't have something for this in its default libraries. There should be #drop method equivalent for this. Surely there's a gem available that would add the functionality to the array class. But who needs gems when you can just break out your own scripts:
#in initializer somewhere
class Array
def exclude(obj)
x = self
x.delete(obj)
x
end
end
I may submit a pull request to the ruby github project for this method. This superman-patch works very well so far.
@aon the classFoois not doing anything. You should remove it.@a = [1,2,3,4,5,6,7,8,9]is the result of a some process.