继承与类常量问题

jhsea3do 发表于 2008-09-19 23:38

# reporter.rb

require 'logger'

class Reporter
# Reporter Attributes
attr :bugs
attr :params

# defined statics
@@logger = Logger.new('/tmp/' + self.to_s.downcase + '.log', 'daily')

# Contruct Method
def initialize
   begin
         @@logger.info('initialize')
   rescue
         # TODO
   end
end
end

class AnotherReporter < Reporter
end

当我 Reporter.new 其实和 AnotherReporter.new 时都会写日志文件，但都只会写入到/tmp/reporter.log，
然尔我现在想把AnotherReporter的日志写入一个/tmp/anotherreporter.log，请问这个代码应该如何写？

sysno 发表于 2008-09-21 15:26

重新定义类变量：
class AnotherReporter < Reporter
@@logger = Logger.new('/tmp/' + self.to_s.downcase + '.log', 'daily')
end

jhsea3do 发表于 2008-09-23 13:20

恩,我后来试演过

其实不能用@@logger，一旦设置了该类变量，一旦被其他类继承就会重载这个类变量

class A
@@prop = 'A'
def test
puts @@prop
end
end

class B < A
@@prop = 'B'
end

a = A.new
b = B.new

a.test #=> B
b.test #=> B

sysno 发表于 2008-09-23 14:42

确实如此，class variable 是会被覆盖的。不好意思，我是初学者。
用类实例变量(class instance variable) 看看这样行不行？
class A
@logger = self.to_s + '.log'
def A.p
puts @logger
end

class B < A
@logger = self.to_s + '.log'
end

A.new.class.p => A.log
B.new.class.p => B.log

jhsea3do 发表于 2008-09-25 11:52

module M
@@T = ''
def test; puts @@T; end;
def stest; puts self.class::T; end;
end

module N
def rtest; self.class.jtest(); end
end

class A
include M
@@T = 'A'
T = 'sA'
def self.itest; puts T; end
def A.jtest; puts A::T; end
def self.ktest; puts T; end
include N
end

class B
include M
@@T = 'B'
T = 'sB'
def self.itest; puts T; end
def B.jtest; puts B::T; end
def self.ktest; A.ktest; end
include N
end

A.new.test    #=> A
B.new.test    #=> B
A.new.stest #=> sA
B.new.stest #=> sB
A.itest       #=> sA
B.itest       #=> sB
A.jtest       #=> sA
B.jtest       #=> sB
A.ktest       #=> sA
B.ktest       #=> sA
A.new.rtest #=> sA
B.new.rtest #=> sB

shitou251314 发表于 2008-09-28 22:17

class A
def initialize(log)
#log
end
end

class B < A
def initialize(log)
super(log)
end
end

页: [1]

Chinaunix's Archiver

继承与类常量问题