I'm trying to solve this assignment:

Create a proc that will check whether a given array of elements are nil or not. Use .nil? to evaluate elements. Print 'true' if the elements are nil and 'false' if the elements has a value?

This is my attempt:

   def check_nill(array1)
      p = Proc.new {|x| x.nil?}
      res= p.call(array1)
      if res == true
        return "true"  
      else  
        return "false"  
      end 
   end
   
   array1=[{},nil,[]]
   result=check_nill(array1)
   puts "#{result}"

Here actually, the output should be "true". But this code gives "false" as output. Can someone tell, what is the reason?

CodePudding user response：

Your method currently checks whether the given object is nil:

check_nill(nil) #=> "true"
check_nill([])  #=> "false"
check_nill(123) #=> "false"

Note that this object can be anything, so your argument name array1 is somehow misleading for this use case. (you might also want to rename the method to check_nil, i.e. with one l)

Here actually, the output should be "true" [...]

I assume that you actually want to check whether any of the array's elements meets a condition, i.e. if the array contains nil. You can use any? with a block for this. From within the block, you can call your proc:

prc = Proc.new { |x| x.nil? }
[{}, nil, []].any? { |element| prc.call(element) }
#=> true

Which can be shortened by converting the proc to a block:

prc = Proc.new { |x| x.nil? }
[{}, nil, []].any?(&prc)
#=> true

You can even get rid of your custom proc and use Symbol#to_proc instead:

[{}, nil, []].any?(&:nil?)
#=> true

There's also all? which checks whether all elements meet the condition, e.g.:

[{}, nil, []].all?(&:nil?)
#=> false

[nil, nil, nil].all?(&:nil?)
#=> true

CodePudding user response：

If I understand the question correctly, you are trying to check whether all the array elements are nil/blank/false or not. If there is any non-nil value present in the array, you want to return true, else false. Here is how you can determine this:

array1 = [{}, nil, []]
array1.all?(&:blank?) # this returns true

array2 = [{}, nil, [], 1]
array1.all?(&:blank?) # this returns false

CodePudding user response：

[nil,nil,nil].all? nil No proc.