Now I’m really confused:
irb(main):001:0> o = Object.new
=> #Object:0x2838c08
irb(main):002:0> o.class == Object
=> true
irb(main):003:0> o.class === Object
=> true
irb(main):004:0> o = Array.new
=> []
irb(main):005:0> o.class == Array
=> true
irb(main):006:0> o.class === Array
=> false
What’s going on here? Why is o.class === Array false?
Ruby version 1.8.0.
John W. Long wrote:
irb(main):004:0> o = Array.new
=>
irb(main):006:0> o.class === Array
=> false
What’s going on here? Why is o.class === Array false?
I think you want this:
irb(main):007:0> Array === o
=> true
See “ri Class#===” for further details.
Regards,
Florian Gross
‘===’ is asking if the rhs is an instance of lhs so:
~ > irb
irb(main):001:0> Array.instance_of? Array
=> false
irb(main):002:0> Array === Array
=> false
irb(main):003:0> Array == Array
=> true
irb(main):004:0> .instance_of? Array
=> true
irb(main):005:0> Array ===
=> true
-a
On Thu, 1 Jan 2004, John W. Long wrote:
Date: Thu, 1 Jan 2004 04:03:39 +0900
From: John W. Long ws@johnwlong.com
Newsgroups: comp.lang.ruby
Subject: Array #== and #===Now I’m really confused:
irb(main):001:0> o = Object.new
=> #Object:0x2838c08
irb(main):002:0> o.class == Object
=> true
irb(main):003:0> o.class === Object
=> true
irb(main):004:0> o = Array.new
=>
irb(main):005:0> o.class == Array
=> true
irb(main):006:0> o.class === Array
=> falseWhat’s going on here? Why is o.class === Array false?
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What’s going on here? Why is o.class === Array false?
I think you want this:
irb(main):007:0> Array === o
=> trueSee “ri Class#===” for further details.
ri Class#=== doesn’t exist for 1.8.0 (I’m on windows). Could you explain
what you mean in further detail?
I’m actually trying to do a case statement:
case o.class
case Array
puts “Array”
…
else
puts “Something Else”
end
–
John Long
http://wiseheartdesign.com
ri Class#=== doesn’t exist for 1.8.0 (I’m on windows).
Try Module#=== instead.
Could you explain
what you mean in further detail?I’m actually trying to do a case statement:
case o.class
case Array
puts “Array”
…
else
puts “Something Else”
end
#=== is really all about case statements, so it’s already optimized for
what you’re trying to do. It’ll do what you want if you just drop the
call to #class:
case o
when Array
puts “Array”
else
puts “Something Else”
end
HTH,
Nathaniel
<:((><
On Dec 31, 2003, at 15:25, John W. Long wrote:
ri Class#=== doesn’t exist for 1.8.0 (I’m on windows).
Try Module#=== instead.
That worked. Thanks.
#=== is really all about case statements, so it’s already optimized for
what you’re trying to do. It’ll do what you want if you just drop the
call to #class:case o
when Array
puts “Array”
else
puts “Something Else”
end
That clears things up. I was confused as to which #=== was called. A little
code to demonstrate your point:
irb(main):005:0> obj = Object.new
=> #Object:0x282d2c8
irb(main):006:0> def obj.===(other)
irb(main):007:1> puts “called”
irb(main):008:1> end
=> nil
irb(main):009:0> case obj
irb(main):010:1> when 1
irb(main):011:1> end
=> nil
irb(main):012:0> case 1
irb(main):013:1> when obj
irb(main):014:1> end
called
=> nil
This explains half of my question. Why does Object.new.class === Object
return true (instead of false like Array.new.class === Array)?
–
John Long
http://wiseheartdesign.com
Because the class Object is an instance of an Object (as is everything
in Ruby), but the class Array is not an instance of an Array.
Basically, Module#=== is just a reversed version of Object#kind_of?, so
these two assertions are saying:
irb(main):001:0> Object.kind_of?(Object)
=> true
irb(main):002:0> Array.kind_of?(Array)
=> false
HTH,
Nathaniel
<:((><
On Dec 31, 2003, at 16:17, John W. Long wrote:
This explains half of my question. Why does Object.new.class === Object
return true (instead of false like Array.new.class === Array)?
so these two assertions are saying:
irb(main):001:0> Object.kind_of?(Object)
=> true
irb(main):002:0> Array.kind_of?(Array)
=> false
I see. Thanks.
–
John Long
www.wiseheartdesign.com