How to check if params[:some][:field] is nil?

Question

I tried code, that plused a lot of people - How to test if parameters exist in rails, but it didn't work():

     if ( params.has_key?([:start_date]) && params.has_key?([:end_date]) )

I think, that is because of complicated params and if I write this:

       if ( params.has_key?([:report][:start_date]) && params.has_key?([:report][:end_date]) )

gives me error

        can't convert Symbol into Integer

this doesn't work too:

           if ( params[:report][:start_date] && params[:report][:end_date] )

gives me error:

        undefined method `[]' for nil:NilClass

It always go into else statement.

Here are my params:

    report: 
    start_date: 01/08/2012
    end_date: 10/08/2012

Can someone help me ?

Possible duplicate of [How to avoid NoMethodError for missing elements in nested hashes, without repeated nil checks?](http://stackoverflow.com/questions/4371716/how-to-avoid-nomethoderror-for-missing-elements-in-nested-hashes-without-repeat) — user513951, Jan 06 '16 at 05:22

score 13 · Accepted Answer · answered Aug 07 '12 at 12:47

13

 if params[:report] && params[:report][:start_date] && params[:report][:end_date]

answered Aug 07 '12 at 12:47

Mikhail Nikalyukin

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Mikhail Nikalyukin, hello from Lutsk, zemelya) – Denys Medynskyi Aug 07 '12 at 12:54
3

Isn't there a more brief and elegant way of doing this? – Magne Nov 25 '15 at 15:33

score 12 · Answer 2 · edited May 23 '17 at 11:47

12

Cross-post answer from here:

Ruby 2.3.0 makes this very easy to do with #dig.

h = { foo: {bar: {baz: 1}}}

h.dig(:foo, :bar, :baz)           #=> 1
h.dig(:foo, :zot, :baz)           #=> nil

edited May 23 '17 at 11:47

Community

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answered Dec 31 '15 at 19:26

steel

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score 7 · Answer 3 · edited May 23 '17 at 11:33

7

I have been looking for a better solution too. I found this one:

Is there a clean way to avoid calling a method on nil in a nested params hash?

params[:some].try(:[], :field)

You get the value or nil if it does not exist.

So I figured let's use try a different way:

params[:some].try(:has_key?, :field)

It's not bad. You get nil vs. false if it's not set. You also get true if the param is set to nil.

edited May 23 '17 at 11:33

Community

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answered Nov 27 '15 at 04:48

Dan Tappin

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Note: `try` is a Rails method, not a Ruby method. – steel Dec 12 '16 at 22:13

score 6 · Answer 4 · answered Aug 07 '12 at 12:47

6

It would seem you need the following

    params[:report].present?

or

    params[:report].nil?

or

    params[:report].empty?

depending on what you are trying to check for

answered Aug 07 '12 at 12:47

Purple Hexagon

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score 1 · Answer 5 · answered Dec 09 '16 at 10:56

1

This works to:

if params[:report].has_key?(:start_date)

And maybe add this so you also check if it is not empty:

&& !params[:report][:start_date].empty?

answered Dec 09 '16 at 10:56

Jelle Hoffman

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How to check if params[:some][:field] is nil?

5 Answers5

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