问题描述
编写一个函数(或某种DSL文件)的最佳方法是让我可以在Ruby中编写这段代码。我将如何构造write_pair函数?
pre $ username =tyndall
write_pair username
#where write_pair用户名输出
用户名:tyndall
有可能吗?寻找最简单的方法来做到这一点。
确实有可能!
我的解决方案通过Object#object_id identity来测试var:
它在绑定传递风格中变成了残缺......
虽然它仅适用于本地变量,但它可以很容易地制作通用增加了其他范围变量列表方法的使用,如 instance_variables
等。
#这个函数必须在这样的地方定义
#...以便捕获变量的绑定... cheesy
#否则我们会被卡住调用者的额外参数
@_binding = binding
def write_pair(p,b = @_binding)
eval(
local_variables.each do | v |
如果eval(v.to_s + \.object_id \)==+ p.object_id.to_s +
puts v.to_s +':'+ \+ p.to_s + \
end
end
,b)
end
#如果绑定是一个问题,只需在这里执行:
# write_pair = lambda {| p | write_pair(p,binding)}
#只是一些测试变量,以确保它能正常工作
username1 =tyndall
username =tyndall
username3 = tyndall
#结果:
write_pair(username)
#username:tyndall
What is the best way to write a function (or something DSLish) that will allow me to write this code in Ruby. How would I construct the function write_pair?
username = "tyndall"
write_pair username
# where write_pair username outputs
username: tyndall
Is it possible to do? Looking for the most simple way to do this.
Sure it is possible!
My solution tests the var by Object#object_id identity: http://codepad.org/V7TXRxmL
It's crippled in the binding passing style ...
Although it works just for local vars yet, it can be easily be made "universal" adding use of the other scope-variable-listing methods like instance_variables
etc.
# the function must be defined in such a place
# ... so as to "catch" the binding of the vars ... cheesy
# otherwise we're kinda stuck with the extra param on the caller
@_binding = binding
def write_pair(p, b = @_binding)
eval("
local_variables.each do |v|
if eval(v.to_s + \".object_id\") == " + p.object_id.to_s + "
puts v.to_s + ': ' + \"" + p.to_s + "\"
end
end
" , b)
end
# if the binding is an issue just do here:
# write_pair = lambda { |p| write_pair(p, binding) }
# just some test vars to make sure it works
username1 = "tyndall"
username = "tyndall"
username3 = "tyndall"
# the result:
write_pair(username)
# username: tyndall
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