Ruby 数组注入(inject)

Question

我正在尝试使用注入(inject)方法记录 10 个线程的平均运行时间，但它给了我这个错误:

undefined method `+' for #<Thread:0x10b211590 dead> (NoMethodError)
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/open-uri.rb:301:in `inject'
    from client_test.rb:13:in `each'
    from client_test.rb:13:in `inject'
    from client_test.rb:13

代码如下:

require 'open-uri'
program_start_time = Time.now
threads = 10.times.map do
  Thread.new do
    time = Time.now
    open('http://ca.yahoo.com/?p=us').read.length
    Time.now-time
  end
end

threads.map &:join
puts threads.inject() { |sum, e| sum + e.value}.to_f / threads.size
puts Time.now - program_start_time

Answer 1

在这种情况下，您需要为 inject 提供一个初始值，因为如果您不这样做，则初始值只是数组中的第一个元素:

puts threads.inject(0) { |sum, e| sum + e.value}.to_f / threads.size