ruby​​：如何知道腳本是否在第三次重試？

Question

begin 
#some routine 
rescue 
retry 
#on third retry, output "no dice!" 
end 

我想讓它在「第三次」重試時打印一條消息。

Answer 1

可能不是最好的解決方案，但一個簡單的方法就是製作一個tries變量。

tries = 0 
begin 
    # some routine 
rescue 
    tries += 1 
    retry if tries <= 3 
    puts "no dice!" 
end 

Answer 2

loop do |i| 
    begin 
    do_stuff 
    break 
    rescue 
    raise if i == 2 
    end 
end 

或

k = 0 
begin 
    do_stuff 
rescue  
    k += 1 
    k < 3 ? retry : raise 
end 

Answer 3

class Integer 
    def times_try 
    n = self 
    begin 
     n -= 1 
     yield 
    rescue 
     raise if n < 0 
     retry 
    end 
    end 
end 

begin 
    3.times_try do 
    #some routine 
    end 
rescue 
    puts 'no dice!' 
end 

Answer 4

寶石attempt被設計用於此，並且提供的嘗試之間等待的選項。我自己並沒有使用它，但它似乎是一個好主意。正如其他人已經證明的那樣，這是塊擅長的東西。

Answer 5

begin 
    #your code 
rescue 
    retry if (_r = (_r || 0) + 1) and _r < 4 # Needs parenthesis for the assignment 
    raise 
end 

Answer 6

還有另一個名爲retry-this的寶石，可以幫助這樣的事情。

ruby-1.9.2-p0 > require 'retry-this' 
ruby-1.9.2-p0 > RetryThis.retry_this(:times => 3) do |attempt| 
ruby-1.9.2-p0 >  if attempt == 3 
ruby-1.9.2-p0 ?>  puts "no dice!" 
ruby-1.9.2-p0 ?> else 
ruby-1.9.2-p0 >  puts "trying something..." 
ruby-1.9.2-p0 ?>  raise 'an error happens' # faking a consistent error 
ruby-1.9.2-p0 ?> end 
ruby-1.9.2-p0 ?> end 
trying something... 
trying something... 
no dice! 
=> nil 

這樣一個創業板的好東西，而不是原始begin..rescue..retry的是，我們能夠避免無限循環或引入一個變量只是爲了這個目的。

Answer 7

def method(params={}) 
    tries ||= 3 
    # code to execute 
rescue Exception => e 
    retry unless (tries -= 1).zero? 
    puts "no dice!" 
end 

Answer 8

Proc.class_eval do 
    def rescue number_of_attempts=0 
    @n = number_of_attempts 
     begin 
     self.call 
     rescue => message 
     yield message, @n if block_given? 
     @n -= 1 
     retry if @n > 0 
     end 
    end 
end 

然後你可以使用它作爲：

-> { raise 'hi' }.rescue(3) 
-> { raise 'hi' }.rescue(3) { |m, n| puts "message: #{m}, 
              number of attempts left: #{n}" }