CODEWITHSUNDEEP
rubykoan
mko
mko

Reputation: 22064

File.open with block vs without

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

code 1 

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

code 2

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

Upvotes: 34

Views: 11790

Answers (2)

Arsen7
Arsen7

Reputation: 12830

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 ;-)

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

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

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

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

Upvotes: 33

DarkDust
DarkDust

Reputation: 92335

No, they do not mean the same. In the first example, the file is automatically closed after the block was processed. In the second example, it's your responsibility to manually call newFile.close.

Upvotes: 43

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