How to test if parameters exist in rails

Question

I m using an IF statement in Ruby on Rails to try and test if request parameters are set   Regardless of whether or not both parameters are set  the first part of the following if block gets triggered  How can I make this part ONLY get triggered if both params  one  and params  two  is set   if  defined  params  one    amp  amp   defined  params  two        do something     elsif  defined  params  one        do something     end

User · Answer

if params  one   amp  amp  params  two       do something     elsif params  one       do something     end

User · Answer

You can also do the following   unless params values at  one   two   three   four  includes  nil       excute code    end    I tend to use the above solution when I want to check to more then one or two params     values at returns and array with nil in the place of any undefined param key   i e    some hash    x 3  y 5  some hash values at  x   random   y    will return the following     3 nil 5      includes  nil  then checks the array for any nil values  It will return true is the array includes nil    In some cases you may also want to check that params do not contain and empty string on false value    You can handle those values by adding the following code above the unless statement    params delete if  key value  value blank     all together it would look like this     params delete if  key value  value blank    unless params values at  one   two   three   four  includes  nil         excute code      end   It is important to note that delete if will modify your hash params  so use with caution    The above solution clearly takes a bit more work to set up but is worth it if you are checking more then just one or two params

User · Answer

I just read this on RubyInRails classes http   api rubyonrails org classes Object html method-i-blank-3F  you can use blank  method which is equivalent to params  one  nil     params  one  empty    e g   if params  one  blank       do something if not exist else     do something if exist end

User · Answer

Just pieced this together for the same problem   before filter  validate params  private  def validate params   return head  bad request unless params present  end  def params present      Set new  w one two three    lt    Set new params keys    amp  amp    params values all  end   the first line checks if our target keys are present in the params  keys using the  lt   subset  operator   Enumerable all  without block per default returns false if any value is nil or false

User · Answer

I am a fan of  params  one  present    Just because it keeps the params sym  form so it s easier to read

User · Answer

Simple as pie   if  params  one  nil  and  params  two  nil     do something    elsif  params  one  nil     do something else    elsif  params  two  nil     do something extraordinary    end

User · Answer

You can write it more succinctly like the following   required     one   two   three  if required all    k  params has key  k      here you know params has all the keys defined in required array else       end

User · Answer

You want has key    if params has key   one   amp  amp  params has key   two     Just checking if params  one   will get fooled by a  there but nil  and  there but false  value and you re asking about existence  You might need to differentiate    Not there at all  There but nil  There but false  There but an empty string    as well  Hard to say without more details of your precise situation

User · Answer

Here s what I do   before action  validate presence   and then following methods       def check presence   params  param1  present   amp  amp  params  param2  present   end   def validate presence   if  check presence     render json                           error                                     message   Bad Request  parameters missing                                    status  500                                                         end  end

User · Answer

if params  one   amp  amp  param  two        excute code    end   You can also check if the parameters are empty by using params  two  empty

User · Answer

use blank  http   api rubyonrails org classes Object html method-i-blank-3F  unless params  one  blank   amp  amp  params  two  blank    will return true if its empty or nil  also    that will not work if you are testing boolean values   since   gt  gt  false blank    gt  true   in that case you could use  unless params  one  to s blank   amp  amp  params  two  to s blank

User · Answer

In addition to previous answers  has key  and has value  have shorter alternatives in form of key  and value   Ruby team also suggests using shorter alternatives  but for readability some might still prefer longer versions of these methods   Therefore in your case it would be something like  if params key   one   amp  amp  params key   two        do something     elsif params key   one        do something     end   NB   key  will just check if the key exists and ignores the whatever possible value  For ex   2 3 3  016  gt  a    first  1  second  nil  third          gt    first  gt 1   second  gt nil   third  gt     2 3 3  017  gt  puts    a key   first      a key   second      a key   third     a key   fourth     true  true  true  false

User · Answer

I try a late  but from far sight answer   If you want to know if values in a  any  hash are set  all above answers a true  depending of their point of view   If you want to test your  GET POST    params  you should use something more special to what you expect to be the value of params  one   something like   if params  one         and  params  two     a-z xy    ignoring parameter  GET POST  as if they where not set  if they dont fit like expected    just a if params  one   with or without nil true detection is one step to open your page for hacking  because  it is typically the next step to use something like select      where params  one       if this is intended or not  active or within or after a framework   an answer or just a hint

User · Answer

A very simple way to provide default values to your params  params  foo       default value

[ruby-on-rails] How to test if parameters exist in rails

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