The following code snippet fully describes the problem, but I have to type all these extra words in to get SO to let me post it.
some_var ||= some_other_var do
# Does this run every time, or only sometimes?
stuff
end
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Throw Away Account
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1Did it occur to you to use the length requirement to ask a question? – Josh Lee May 09 '17 at 21:38
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@JoshLee The question is right there in the title. Did you not see it? – Throw Away Account May 09 '17 at 22:23
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There's nothing *to* search. Google does not accept `||=` as a search term. – Throw Away Account May 09 '17 at 22:24
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Titles aren't questions, instead they introduce the subject. Your question is poorly asked and shows very little effort. "[ask]" and the linked pages would be good reading. – the Tin Man May 09 '17 at 22:24
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1Google does if you put it in quotes. https://www.google.com/search?q=site:stackoverflow.com+ruby+%2B+%22%7C%7C=%22+block – the Tin Man May 09 '17 at 22:28
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The search returns nothing relevant, so apparently nobody has documented this usage. – Throw Away Account May 09 '17 at 22:32
1 Answers
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Such code will be evaluated just like any other with a ||= operator. If some_var is nil or false the function will run and return value will be assigned to some_var; otherwise the value of some_var will be returned. See What does ||= (or-equals) mean in Ruby? for reference.
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But what about the block? I found some code that puts a block after the assignment (as shown in my example), which makes absolutely no sense and isn't documented in any place that I know of. AFAIK, it should be a syntax error. In fact, the question you linked to has no answers that discuss putting a block after the `||=` assignment. – Throw Away Account May 09 '17 at 22:28
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The block is simply a "special type of argument" passed to a method (in your example the method is `some_other_var`); you don't pass a block to a variable. The method with a passed block will be evaluated and its return value will be assigned to `some_var`. – xlts May 09 '17 at 22:37
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Damn Ruby and its confusing syntax! I failed to remember that `some_other_var` can actually be a method call. Thanks. – Throw Away Account May 09 '17 at 22:41