How I can check if an object is null in ruby on rails 2

Question

I want to check when my object  objectname is not equal to null to show the values of the  objectname else to show that no values found    I tried this    lt   if   objectname    null  then   gt    but I m getting an error

User · Answer

You can use the simple not flag to validate that. Example

if !@objectname

This will return true if @objectname is nil. You should not use dot operator or a nil value, else it will throw

*** NoMethodError Exception: undefined method `isNil?' for nil:NilClass

An ideal nil check would be like:

!@objectname || @objectname.nil? || @objectname.empty?

User · Answer

In your example  you can simply replace null with  nil and it will work fine   require  erb   template    lt  lt EOS  lt   if   objectname    nil  then   gt     objectname is not nil  lt   else   gt     objectname is nil  lt   end   gt  EOS   objectname   nil ERB new template  nil    gt    result     gt      objectname is nil n    objectname    some name  ERB new template  nil    gt    result     gt      objectname is not nil n    Contrary to what the other poster said  you can see above that then works fine in Ruby  It s not common  but it is fine    blank  and  present  have other implications  Specifically  if the object responds to  empty   they will check whether it is empty  If you go to http   api rubyonrails org  and search for  blank    you will see what objects it is defined on and how it works  Looking at the definition on Object  we see  An object is blank if it   s false  empty  or a whitespace string  For example                   nil      and    are all blank   You should make sure that this is what you want   Also  nil is considered false  and anything other than false and nil is considered true  This means you can directly place the object in the if statement  so a more canonical way of writing the above would be  require  erb   template    lt  lt EOS  lt   if  objectname   gt     objectname is not nil  lt   else   gt     objectname is nil  lt   end   gt  EOS   objectname   nil ERB new template  nil    gt    result     gt      objectname is nil n    objectname    some name  ERB new template  nil    gt    result     gt      objectname is not nil n    If you explicitly need to check nil and not false  you can use the  nil  method  for which nil is the only object that will cause this to return true   nil nil               gt  true false nil             gt  false Object new nil        gt  false

User · Answer

You can check if an object is nil  null  by calling present  or blank      object present    this will return false if the project is an empty string or nil    or you can use   object blank    this is the same as present  with a bang and you can use it if you don t like  unless   this will return true for an empty string or nil

User · Answer

it s nilin Ruby  not null  And it s enough to say if  objectname to test whether it s not nil  And no then  You can find more on if syntax here   http   en wikibooks org wiki Ruby Programming Syntax Control Structures if

User · Answer

Now with Ruby 2 3 you can use  amp   operator   lonely operator   to check for nil at the same time as accessing a value    person amp  spouse amp  name   https   en wikibooks org wiki Ruby Programming Syntax Operators Other operators    Use  try instead so you don t have to keep checking for nil    http   api rubyonrails org classes Object html method-i-try   person try  spouse  try  name    instead of   person spouse name if  person  amp  amp   person spouse

[ruby-on-rails] How I can check if an object is null in ruby on rails 2?

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