Hi
Could you please tell me when to use .nil? , .empty?, .blank? .What
are the difference between them… For example I have
params[:company][:whichCompany]
And to check for it is null I first attempted all these and finally the
following worked
if !params[:company][:whichCompany].empty?
So now really i am confused .Please tell me the differnce
Could you please tell me when to use .nil? , .empty?, .blank? .What
are the difference between them… For example I have
params[:company][:whichCompany]
And to check for it is null I first attempted all these and finally the
following worked
if !params[:company][:whichCompany].empty?
So now really i am confused .Please tell me the differnce
nil? tests whether the object is exactly nil, that is whether it is
the one and only want instance of NilClass.
empty? is a method some objects respond to. You need to check the
documentation for each case. For example, and empty array is one that
is not nil (it is an array right?) and has no elements. An empty
string is one that is not nil (it is a string right?) and has no
bytes, nothing.
The blank? method you ask for does not belong to Ruby, it is a Rails
extension: Peak Obsession.
.nil? tests whether the receiver is the nil object, that is the only
instance
of class NilClass, which is often used to indicate an invalid value.
This
method is defined in class Object, and thus is availlable for every
object.
The other two methods, instead, are defined only for specific classes,
so the
answer depends. Usually, empty? is used to test whether an object is
“empty”,
for some class-depending meaning of empty. For example, String#empty?
returns
true if the string contains no characters, Array#empty? and Hash#empty?
returns true if the array or hash has no entries. Other classes may
define an
empty? method in other ways. Note that, unlike nil?, empty? isn’t
defined for
all classes.
Regarding blank?, I never heard of it, so I can’t help you. You should
look at
the documentation of the class defining it.
Here are some examples about nil? and empty?
nil.nil?
=> true
false.nil?
=> false
1.nil?
=> false
0.nil?
=> false
“”.nil?
=> false
[].nil?
=> false
“”.empty?
=> true
“abc”.empty?
=> false
[].empty?
=> true
[1, 2, 3].empty?
=> false
1.empty?
=> NoMethodError
The last example means that the empty? method is not defined for class
Fixnum
Isn’t .nil? and .empty? in a way testing for a very similar
situation?
Not in Ruby. empty? is true for a String of length 0. The value of the
String is not Nil. It turns out that Nil is very important in
evaluations
since it’s one of the two items in Ruby that evaluates to false.
irb(main):001:0> str = String.new
=> “”
irb(main):002:0> str.length
=> 0
irb(main):003:0> if str then puts ‘a zero-length string is still a
string’
end
a zero-length string is still a string
=> nil
irb(main):004:0> str = nil
=> nil
irb(main):005:0> if str.nil? then puts ‘assigning a nil value
essentially
kills
the object’ end
assigning a nil value essentially kills the object
=> nil.
Could you please tell me when to use .nil? , .empty?, .blank? .What
are the difference between them… For example I have
params[:company][:whichCompany]
And to check for it is null I first attempted all these and finally the
following worked
if !params[:company][:whichCompany].empty?
So now really i am confused .Please tell me the differnce
nil? tests whether the object is exactly nil, that is whether it is
the one and only want instance of NilClass.
empty? is a method some objects respond to. You need to check the
documentation for each case. For example, and empty array is one that
is not nil (it is an array right?) and has no elements. An empty
string is one that is not nil (it is a string right?) and has no
bytes, nothing.
The blank? method you ask for does not belong to Ruby, it is a Rails
extension: Peak Obsession.
if I populated a[:real] with false, why does ‘.blank?’ return true?
That’s confusing. But hey, if you can’t win them, join them. I love Ruby
and Rails!
On Thu, Jul 15, 2010 at 7:45 AM, Michael N. [email protected]
wrote:
I personally find this confusing:
a[:real]=false
a[:real] Â Â => false
a[:real].blank?   => true   ??
if I populated a[:real] with false, why does ‘.blank?’ return true?
That’s confusing. But hey, if you can’t win them, join them. I love Ruby
and Rails!
It should work
$ script/console
Loading development environment (Rails 2.3.2)