Ruby on Rails turn each iteration into an array

Question

I feel like this is such an easy question

<% @state.cities.each do |city| %>
   <%= city.id %>
<% end %>

puts the ids as follows:

1
2
3 etc...

How do I turn the iteration into an array?

so it outputs as follows:

[1,2,3,4,etc...] 

Answer 1

There is a method that does just that!

What you are looking for is the map method.

Creates a new array containing the values returned by the block.

http://apidock.com/ruby/Array/map

The documentation states, creates an array containing the values returned by a block.

@state.map do |state|
  state.id
end
=> [1,2,3,...]

Which is the same as:

@state.map(&:id)
=> [1,2,3,...]

But uses the Ruby Enumerable shorthand.

Answer 2

您可以使用map ：

<%= @state.map(&:id) %>

Answer 3

@state.map(&:id)会给您相同的结果！