File.open 带块 vs 不带 [英] File.open with block vs without

问题描述

我有一个关于 Block 的问题，这两个代码的意思一样吗?

I have a question about Block, do the two codes mean the same?

代码 1

File::open('yozloy.txt','w') do |f|
  f << 'Some contains'
end

代码 2

newFile = File::open('yozloy.txt','w')
newFile << 'Some contains'

推荐答案

DarkDust 已经说过，这些方法是不同的.我会再解释一下这些块，因为我想我能猜到你问这个问题的原因;-)

DarkDust already said that these methods are different. I'll explain you the blocks a little more, as I suppose that I can guess why you asked this question ;-)

ruby 中的块只是某些方法的参数.这不仅仅是一种不同的语法.

The block in ruby is just a parameter for some method. It's not just a different syntax.

接受(可选)块的方法通常有一个条件来测试它们是否被块调用.

Methods which accept (optional) blocks usually have a condition to test whether they have been called with block, or without.

考虑这个非常简单的例子:(真正的 File.open 是类似的，但它确保文件关闭，即使你的块引发错误，例如)

Consider this very simplified example: (the real File.open is similar, but it ensures the file is closed even if your block raises an error, for example)

def open(fname)
  self.do_open(fname)
  if block_given?
    yield(self) # This will 'run' the block with given parameter
    self.close
  else
    return self # This will just return some value
  end
end

一般来说，每种方法在有块或没有块的情况下工作(工作)可能不同.应始终在方法文档中说明.

In general, every method may work (works) differently with a block or without a block. It should be always stated in the method documentation.

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