From: Farrel Lifson <farrel.lifson@...>
Date: 2006-07-27T17:18:03+09:00
Subject: Re: ||= in an expression

On 27/07/06, rejoc <rejoc@freefree.fr> wrote:
> Hello,
>
> I new to Ruby and curious about this language I do use (yeet).
>
> I was browsing through some libraries/modules and I found a line looking
> like
>
> a[:i] ||= "a string"
>
> I could not find this syntax in any manual online (and googling "||=" is
> not of much help :-( )
>
> Can anyone tell me what it means
>
> TiA
>
>

In Ruby

nil || anObject

will return anObject and

anotherObject || anObject

will return anotherObject (assuming it's value isn't nil)

The expression

a[:i] ||= "a string"

is equivalent to

a[:i] = a[:i] || "a string"

(sort of like 'num+= 1' is the same as 'num = num + 1')If a[:i] is not
nil then it will remain unchanged. If it is nil then it will be set to
"a string".

Farrel