# Assignment if key\_exist? in Hash

**URL:** <https://www.ruby-forum.com/t/assignment-if-key-exist-in-hash/133503>\
**Category:** Ruby\
**Created:** [April 1, 2008, 5:06am UTC](https://www.ruby-forum.com/t/assignment-if-key-exist-in-hash/133503 "2008-04-01T05:06:34Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [April 1, 2008, 5:06am UTC](https://www.ruby-forum.com/t/assignment-if-key-exist-in-hash/133503/1 "2008-04-01T05:06:34Z")

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Hi all,

I have a bunch of lines like:

> foo = some\_hash[“some\_key”] if some\_hash.has\_key?(“some\_key”)

This feels awkward and cumbersome, so I would imagine there is a more  
idiomatic way to write it.

Thanks,  
-d

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**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [April 1, 2008, 5:31am UTC](https://www.ruby-forum.com/t/assignment-if-key-exist-in-hash/133503/2 "2008-04-01T05:31:10Z")

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From: darren kirby [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]

# \> foo = some\_hash[“some\_key”] if some\_hash.has\_key?(“some\_key”)

try,

foo = some\_hash[“some\_key”] || foo

kind regards -botp

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**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [April 1, 2008, 5:57am UTC](https://www.ruby-forum.com/t/assignment-if-key-exist-in-hash/133503/3 "2008-04-01T05:57:31Z")

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On Mar 31, 2008, at 9:30 PM, Peña, Botp wrote:

> foo = some\_hash[“some\_key”] || foo

that replaces even if the key is set to ‘false’, ‘nil’, or if the has  
does not have the key… but prolly what OP wants…

regards.

a @ [http://codeforpeople.com/](http://codeforpeople.com/)

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<div class="post-metadata">

**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [April 1, 2008, 5:45am UTC](https://www.ruby-forum.com/t/assignment-if-key-exist-in-hash/133503/4 "2008-04-01T05:45:48Z")

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quoth the Peña, Botp:

> From: darren kirby [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)]
> 
> # \> foo = some\_hash[“some\_key”] if some\_hash.has\_key?(“some\_key”)
> 
> try,
> 
> foo = some\_hash[“some\_key”] || foo
> 
> kind regards -botp

That’s the one.  
Thanks botp,

-d

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**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [April 1, 2008, 6:16am UTC](https://www.ruby-forum.com/t/assignment-if-key-exist-in-hash/133503/5 "2008-04-01T06:16:16Z")

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quoth the ara.t.howard:

> On Mar 31, 2008, at 9:30 PM, Peña, Botp wrote:
> 
> > foo = some\_hash[“some\_key”] || foo
> 
> that replaces even if the key is set to ‘false’, ‘nil’, or if the hash  
> does not have the key…

I don’t understand…If the hash key doesn’t exist then foo retains its  
original value. That is the behaviour I require:

> foo = “Some String”  
> h = {}  
> foo = h[“none\_such”] || foo  
> =\> “Some String”  
> h = {“some\_key”=\>“some value”}  
> foo = h[“some\_key”] || foo  
> =\> “some value”

-d

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<div class="post-metadata">

**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [April 1, 2008, 6:26am UTC](https://www.ruby-forum.com/t/assignment-if-key-exist-in-hash/133503/6 "2008-04-01T06:26:14Z")

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What he’s saying is if you want to retain the value of “false” or  
“nil”, that won’t work too well

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**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [April 1, 2008, 6:36am UTC](https://www.ruby-forum.com/t/assignment-if-key-exist-in-hash/133503/7 "2008-04-01T06:36:46Z")

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quoth the Julian L.:

> What he’s saying is if you want to retain the value of “false” or  
> “nil”, that won’t work too well

Ahh, OK.

Not a prob. In my use case the hash key will be set to a string or it  
will not  
exist.

Thanks all,  
-d

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<div class="post-metadata">

**Author:** ![darren\_kirby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/ed8c4c/32.png) [@darren\_kirby](https://www.ruby-forum.com/u/darren_kirby)\
**Post date:** [April 1, 2008, 8:29am UTC](https://www.ruby-forum.com/t/assignment-if-key-exist-in-hash/133503/8 "2008-04-01T08:29:26Z")

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darren kirby wrote:

> quoth the Julian L.:
> 
> > What he’s saying is if you want to retain the value of “false” or  
> > “nil”, that won’t work too well
> 
> Ahh, OK.
> 
> Not a prob. In my use case the hash key will be set to a string or it will not  
> exist.

You could also use  
foo = hash.fetch(“some\_key”, foo)