From: Hank Gong <hankgong@...>
Date: 2005-12-21T20:40:00+09:00
Subject: A interesting obervation about object_id method

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#integer
puts "For number"
a=3D1
b=3Da
puts a.object_id
puts b.object_id
b=3D2
puts b.object_id
b=3D1
puts b.object_id

>>For number
>>3
>>3
>>5
>>3

#You can see that:
# 1) for the same integer, the object_id is the same
# 2) When b change, a will not change

#string
puts "For String"
a=3D"Hello world!"
b=3Da
puts a.object_id
puts b.object_id
b=3D"Bye world!"
puts b.object_id
b=3D"Hello world!"
puts b.object_id
b=3D"Why?"
puts b.object_id
b=3D"Why?"
puts b.object_id
puts "Why?".object_id

>>For String
>>40660112
>>40660112
>>40660076
>>40660052
>>40660028
>>40660004
>>40659980

# 1) When you assign b=3Da, the object_id of b and a is same
# 2) but when you change b's string, the b's object_id will change
# 3) if you change b's string again, the b's object_id will also change

puts "For Array"
a=3D[1,2,3,4]
b=3Da
puts a.object_id
puts b.object_id
b[2]=3D100
puts b.object_id
puts b.join(",")
puts a.object_id
puts a.join(",")

>>For Array
>>21563588
>>21563588
>>21563588
>>1,2,100,4
>>21563588
>>1,2,100,4
# 1) when b=3Da, the b and a will be the same object_id
# 2) when you change b's elements, b's object_id will be same
# 3) when you change b's elements, a will also be changed

I think it's very interesting experiments. Hope someone can give us a clear
explanation.

--
Huazhi Gong (Hank)

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