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Guarded Assignment in Ruby
written by Steven Bristol on December 16th, 2008
Most people familiar with Ruby are familiar with the Ruby operator ||=. What it does is assign the value of the right to the variable on the left if left is nil (or false). Here is an example:
Most people however are not familiar with the corollary operator &&=. What it does is assign the value of the right to the variable on the left if left is not nil (or false). Here is an example:
Here is an example of how one might use &&=. The idea is that you have an array of something and you only really care if they all completed or not. I used AR::Base.save to show a poor man’s transactions.
5 Responses to “Guarded Assignment in Ruby”
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Ow, my head! You are correct, I’d never thought there was a corollary to ||=. Examples of where this might be useful are escaping me at the moment, but thanks.
I saw this a couple of weeks ago and didn’t know what it was… I also couldn’t figure out how to google for what it was. So… thanks!
Can anyone show me a small example where this might come in handy?
I didn’t know of it, but it seems kind of nifty. Thanks for yet another ruby tip to make my code less readable to others. Yay :)
I added an example.
Yeah, finding good places to use &&= can be tricky.
One way I’ll often use it is for string manipulation.
foo &&= foo.squeeze
If you end up doing more than one of these in a row, you’d probably want to make it an if block.