问题
Is there some difference between Time.now and Time.new (without parameters)? May be difference in memory management or some small details?
回答1:
now is an alias for new. There's no difference between them. Jeff price's get to answer(and his answer is also correct, please up vote his answer if you like this) first, because I was writing and running this benchmark:
Ruby 2.1.2(MRI):
Rehearsal ----------------------------------------------------------------------------
Time.new 0.670000 0.000000 0.670000 ( 0.679709)
Time.now 0.880000 0.010000 0.890000 ( 0.881899)
------------------------------------------------------------------- total: 1.560000sec
user system total real
Time.new 0.720000 0.000000 0.720000 ( 0.719453)
Time.now 0.740000 0.010000 0.750000 ( 0.742711)
Rehearsal ----------------------------------------------------------------------------
Time.new 0.810000 0.000000 0.810000 ( 0.811874)
Time.now 0.830000 0.000000 0.830000 ( 0.831346)
------------------------------------------------------------------- total: 1.640000sec
user system total real
Time.new 0.790000 0.010000 0.800000 ( 0.800082)
Time.now 0.740000 0.000000 0.740000 ( 0.749995)
Rehearsal ----------------------------------------------------------------------------
Time.new 0.680000 0.010000 0.690000 ( 0.690337)
Time.now 0.850000 0.000000 0.850000 ( 0.856800)
------------------------------------------------------------------- total: 1.540000sec
user system total real
Time.new 0.790000 0.010000 0.800000 ( 0.792666)
Time.now 0.770000 0.000000 0.770000 ( 0.777414)
Rehearsal ----------------------------------------------------------------------------
Time.new 0.590000 0.010000 0.600000 ( 0.594650)
Time.now 0.710000 0.010000 0.720000 ( 0.717067)
------------------------------------------------------------------- total: 1.320000sec
user system total real
Time.new 0.870000 0.000000 0.870000 ( 0.872646)
Time.now 0.680000 0.010000 0.690000 ( 0.687092)
Rehearsal ----------------------------------------------------------------------------
Time.new 0.780000 0.010000 0.790000 ( 0.786419)
Time.now 0.780000 0.000000 0.780000 ( 0.789049)
------------------------------------------------------------------- total: 1.570000sec
user system total real
Time.new 0.760000 0.010000 0.770000 ( 0.768194)
Time.now 0.790000 0.010000 0.800000 ( 0.790981)
Run benchmark yourself:
n = 1000000
5.times do
Benchmark.bmbm(40) do |x|
x.report("Time.new"){ n.times { Time.new } }
x.report("Time.now"){ n.times { Time.now } }
end
end
回答2:
There is no difference.
Time.now is an alias for ::new. Returns a Time object initialized to the current system time.
http://www.ruby-doc.org/core-2.1.4/Time.html#method-c-now
回答3:
Using Ruby 2.4.1 and Rails 5.0.3 When using travel_to in tests Time.new does not get affected by it but Time.now does change because of it
来源：https://stackoverflow.com/questions/26719216/time-now-vs-time-new-in-ruby