问题
Here's the line of code I'm trying to wrap my head around:
Category.all.map(&:id).each { |id| Category.reset_counters(id, :products) }
Hoping someone can help me understand what (&:id) is doing and how it impacts the rest of the line? I believe it turns the symbol :id into a proc that'll respond to id?!? But then it gets confusing...
Thanks in advance!
回答1:
Category.all.map(&:id)
is shorthand for
Category.all.map { |a| a.id }
as for how it affects the rest of the line, the above section returns all id values as a single Array. This Array of ids is then passed into another call to each, which iteratively passes each id into reset_counters.
来源：https://stackoverflow.com/questions/18523675/what-exactly-does-id-do-in-product-all-mapid