“中”红宝石方法有什么作用？

Question

It's a bit hard to search for it. This might actually be a Rails method.

Answer 1

If you want to know what any method does, just do "ri the_method" from the shell. In this case, "ri in" reveals Date#in . "ri Date.in" gives:

Alias for #since

In turn, "ri Date.since" gives:

Converts Date to a Time (or DateTime if necessary) with the time portion set to the beginning of the day (0:00) and then adds the specified number of seconds

And yes, it's in ActiveSupport.

Answer 2

"in" is used as an alternative to the array.each do |a| syntax

array = [1,2,3,4]

for a in array
 puts a
end

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