Ruby uses a short piece of code to test your reference type skill

Class fixnum attr_accessor: valueendx = 1 p x. object_idx.value = "anleb" P x. value. object_iddef change (x) P x. object_id p x. value. object_id x = 2 # pointer change X. value = "mr. W "P x. object_id p x. value. object_id # x pointer changed here GC recycles endchange xp x. valuep X. object_idp X. value. object_id print 3229503603229503605229502901 "anleb" 322950360
 

This sectionCodeWell, this is the case where we can't change the value passed in a common method. Not to mention it, we all know that the internal variables of the method change the pointer and exit the method, the pointer is destroyed, and X returns to the top-level domain X, which is the original pointer.

Now, why does the # x = 2 comment out and the result change? The problem lies in attr_accessor: value.
This code is equivalent:

 
Def value = (value) @ value = value end def value @ value end
 

Note that no, the returned value is @ value, so the value in the object will be modified. I don't know if it's true or not.

Class fixnum attr_accessor: value end x = 1 p x. object_id X. value = "anleb" P x. value. object_id def change (x) P x. object_id p x. value. object_id # x = 2 X. value = "mr. W "P x. object_id p x. value. object_id end change x P x. value p x. object_id p x. value. object_id # result: 3 5875824 3 5875824 3 5875704 1 "mr. W "3 5875704
 

We have done everything we can about whether the value or reference passed in this method on the Forum. Here we will not talk about the basics.
Check the Code. If # x = 2 is not commented, the result of the Code is as follows: