From: Robert Dober <robert.dober@...>
Date: 2006-07-27T17:34:33+09:00
Subject: Re: ||= in an expression

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On 7/27/06, 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] ||=3D "a string"
>
> I could not find this syntax in any manual online (and googling "||=3D" i=
s
> not of much help :-( )
>
> Can anyone tell me what it means
>
> TiA
>
>
It is very useful as

var ||=3D expr

is a shortcut for

var =3D expr unless defined? var and var

which means if var is defined and evaluates to true it is left alone
however if var is not defined or evaluates to false it is assigned expr.
That means also that
var ||=3D expr
will overwrite nil *and* false values in var, a fact which seems to be
overseen sometimes.

Cheers
Robert

--=20
Deux choses sont infinies : l'univers et la b=EAtise humaine ; en ce qui
concerne l'univers, je n'en ai pas acquis la certitude absolue.

- Albert Einstein

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