# Passing only a hash key, with no value, as an option **URL:** \ **Category:** Ruby\ **Created:** [March 12, 2008, 1:08pm UTC](https://www.ruby-forum.com/t/passing-only-a-hash-key-with-no-value-as-an-option/131677 "2008-03-12T13:08:58Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [March 12, 2008, 1:08pm UTC](https://www.ruby-forum.com/t/passing-only-a-hash-key-with-no-value-as-an-option/131677/1 "2008-03-12T13:08:58Z")
I’m using the method of parameter passing where i have one ‘regular’ parameter and then a hash of options: def chunkify(something, options = {}) … end I want to have it so that the user can just pass a key through without having to set it to anything, eg dinner = chunkify(bacon, :extra\_fine) However, ‘extra\_fine’ is just being treated as a symbol, rather than a hash key, and so ‘options’ is simply the symbol :extra\_fine, rather than the hash {:extra\_fine =\> nil}. I can fix this by passing :extra\_fine =\> true to the method, but can i set up the method so it will just take the hash key, and maybe some other hash\_keys, some with and some without values? thanks max ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [March 12, 2008, 1:20pm UTC](https://www.ruby-forum.com/t/passing-only-a-hash-key-with-no-value-as-an-option/131677/2 "2008-03-12T13:20:35Z")
2008/3/12, Max W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > dinner = chunkify(bacon, :extra\_fine) > > However, ‘extra\_fine’ is just being treated as a symbol, rather than a > hash key, and so ‘options’ is simply the symbol :extra\_fine, rather than > the hash {:extra\_fine =\> nil}. > > I can fix this by passing :extra\_fine =\> true to the method, but can i > set up the method so it will just take the hash key, and maybe some > other hash\_keys, some with and some without values? Nope. You will have to use chunkify(something, \*options) and do the processing yourself. Note that in no case can you mix Hash entries with and without values. But you can do irb(main):006:0\> def x(\*a)p a end =\> nil irb(main):007:0\> x(:foo, :bar =\> 2) [:foo, {:bar=\>2}] =\> nil irb(main):008:0\> Kind regards robert ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [March 12, 2008, 1:22pm UTC](https://www.ruby-forum.com/t/passing-only-a-hash-key-with-no-value-as-an-option/131677/3 "2008-03-12T13:22:57Z")
Hi – On Wed, 12 Mar 2008, Max W. wrote: > dinner = chunkify(bacon, :extra\_fine) > > However, ‘extra\_fine’ is just being treated as a symbol, rather than a > hash key, and so ‘options’ is simply the symbol :extra\_fine, rather than > the hash {:extra\_fine =\> nil}. > > I can fix this by passing :extra\_fine =\> true to the method, but can i > set up the method so it will just take the hash key, and maybe some > other hash\_keys, some with and some without values? You’re over-thinking this a bit. :extra\_fine isn’t any more a hash key than 100 is in this: ``` do_something(100) ``` The only thing that tells Ruby that you want a hash as the last argument, in the absence of curly braces, is the hash separator (=\>). ``` do_something(100 => "C") ``` There’s also no such thing as a hash key that isn’t part of a hash. It sounds like what you want to do is pass multiple objects to your method and create a hash from them inside the method. David ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [March 12, 2008, 1:43pm UTC](https://www.ruby-forum.com/t/passing-only-a-hash-key-with-no-value-as-an-option/131677/4 "2008-03-12T13:43:06Z")
2008/3/12, Max W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > I know what you’re saying, it is a bit clumsy. Pardon me, but it seems David’s words did not sink in since you are still talking about a Hash key where you mean “symbol”. > presence of a hash key acts like a switch which i can test with > > if options.has\_key? :foo > do\_extra\_stuff > end > > I thought i’d seen this functionality in rails, where we can pass just a > hash key without bothering to set it, if we want to switch something on > or off. If you need a set of boolean flags then you can just use an array irb(main):008:0\> def x(\*opts) irb(main):009:1\> settings = opts.inject({}){|h,o| h[o]=true;h} irb(main):010:1\> end =\> nil irb(main):011:0\> x(:foo, :lazy) =\> {:lazy=\>true, :foo=\>true} irb(main):012:0\> Kind regards robert ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [March 12, 2008, 2:25pm UTC](https://www.ruby-forum.com/t/passing-only-a-hash-key-with-no-value-as-an-option/131677/5 "2008-03-12T14:25:58Z")
Max W. wrote: > I’m using the method of parameter passing where i have one ‘regular’ > parameter and then a hash of options: > > def chunkify(something, options = {}) > … > end > > I want to have it so that the user can just pass a key through without > having to set it to anything, eg > > dinner = chunkify(bacon, :extra\_fine) > > However, ‘extra\_fine’ is just being treated as a symbol, rather than a > hash key, and so ‘options’ is simply the symbol :extra\_fine, rather than > the hash {:extra\_fine =\> nil}. extra\_fine is a symbol, as other people pointed out. If that’s the only concern, then how about def chunkify(something, options={}) options={options=\>true} unless options.kind\_of(Hash) … end options=:extra\_fine ;=\> :extra\_fine options={options=\>true} unless options.kind\_of?(Hash) ;=\>{:extra\_fine=\>true} Then your normal processing can continue. ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [March 12, 2008, 2:30pm UTC](https://www.ruby-forum.com/t/passing-only-a-hash-key-with-no-value-as-an-option/131677/6 "2008-03-12T14:30:42Z")
> options=:extra\_fine ;=\> :extra\_fine > options={options=\>true} unless options.kind\_of?(Hash) > ;=\>{:extra\_fine=\>true} > > Then your normal processing can continue. OK, point taken 🙂 That’s a nice snippet, thanks. cheers all max ---
**Author:** ![cmaxvv](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/85f322/32.png) [@cmaxvv](https://www.ruby-forum.com/u/cmaxvv)\ **Post date:** [March 12, 2008, 1:35pm UTC](https://www.ruby-forum.com/t/passing-only-a-hash-key-with-no-value-as-an-option/131677/7 "2008-03-12T13:35:50Z")
> There’s also no such thing as a hash key that isn’t part of a hash. It > sounds like what you want to do is pass multiple objects to your > method and create a hash from them inside the method. > > David Hi David I know what you’re saying, it is a bit clumsy. Where i’m coming from is that i often use a lot of options that are set to true by the user of the method if they want to use them, which does work nicely due to options[:foo] evaluating to nil if the user didn’t set it, allowing me to have tests like if options[:foo] #missing key equivalent to :foo =\> false do\_extra\_stuff end I just thought it would be even nicer to have the user just be able to pass the hash key, rather than have to keep adding “=\> true”. So the presence of a hash key acts like a switch which i can test with if options.has\_key? :foo do\_extra\_stuff end I thought i’d seen this functionality in rails, where we can pass just a hash key without bothering to set it, if we want to switch something on or off.