"对于" vs“每个”在Ruby中 [英] "for" vs "each" in Ruby

问题描述

我刚刚在Ruby中有一个关于循环的问题。这两种迭代方式有什么不同？

 ＃way 1 
 @ collection.each do |项目| 
＃做任何
结束
 
＃方式2 
在@collection中的项目
＃做任何
结束
  

只是想知道这些是否完全一样，或者可能存在细微的差异（可能当 @collection 是nil）。


解决方案

这是唯一的区别：



each：



  irb> [1,2,3] .each {| x | } 
 => [1，2，3] 
 irb> x 
 NameError：未定义的局部变量或方法`x'for main：Object $ b $ from（irb）：2 
 from：0 
   
 
 $ b 
  for：  
 $ b 
  irb>对于[1,2,3]中的x;结束
 => [1，2，3] 
 irb> x 
 => 3 
  
通过 for 循环，迭代器变量仍然生活在块完成后。使用每个循环，除非它在循环开始之前已经被定义为局部变量，否则它不会。
 
 
 <除此之外，对于方法来说只是的语法糖。
 
 
 
当 @collection 是 nil 两个循环都抛出一个异常：
 
 
例外：未定义的局部变量或方法`@collection'为main：Object 
 
 
I just had a quick question regarding loops in Ruby. Is there a difference between these two ways of iterating through a collection?
# way 1
@collection.each do |item|
  # do whatever
end

# way 2
for item in @collection
  # do whatever
end
Just wondering if these are exactly the same or if maybe there's a subtle difference (possibly when @collection is nil).
解决方案
This is the only difference:

each:
irb> [1,2,3].each { |x| }
  => [1, 2, 3]
irb> x
NameError: undefined local variable or method `x' for main:Object
    from (irb):2
    from :0
for:
irb> for x in [1,2,3]; end
  => [1, 2, 3]
irb> x
  => 3
With the for loop, the iterator variable still lives after the block is done. With the each loop, it doesn't, unless it was already defined as a local variable before the loop started.

Other than that, for is just syntax sugar for the each method.

When @collection is nil both loops throw an exception:

  
Exception: undefined local variable or method `@collection' for main:Object


                        
这篇关于&QUOT;对于&QUOT; vs“每个”在Ruby中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！