Ruby Syntax: attr_reader, attr_writer, and attr_accessor

Attr_reader: abc

You can use

Instance name. abc obtains the value of this variable, but cannot be modified. It is equivalent

Def abc
Return @ abc
End

By the way, attr_writer and attr_accessor,
Attr_writer: abc, which is equivalent

Def abc = (abc)
@ Abc = abc
End

In this case, you cannot obtain the value of abc through Instance name. abc, but you can
Instance name. abc = expression set abc Value

Attr_accessor: abc

Equivalent

Def abc
Return @ abc
End
Def abc = (abc)
@ Abc = abc
End

You can use the Instance name. abc or the Instance name. abc = value.

Sometimes, obtaining/setting is not a simple internal variable assignment. Therefore, you must use attr_reader and attr_writer to partially simplify the definition description.
See Game_Battler's
Attr_reader: hp
And
Def hp = (hp)
Two methods