Reflection on method parameters in Ruby
Take the following class:
class Automator
def fill_specific_form(fields)
fields.each_pair do |key, value|
puts "Setting '#{key}' to '#{value}'"
end
end
end
a = Automator.new
a.fill_specific_form :first_name => "Mads", :last_name => "Mobæk"
# => Setting 'first_name' to 'Mads'
# => Setting 'last_name' to 'Mobæk'
Is it possible to do the same without a hash? Since all parameters are required, I want a method with the following signature:
fill_specific_form(first_name, last_name)
In my mind this would be possible by having the method body reflect and iterate over its parameters, thus achieving the same result.
How would you implement this? Does a pattern/idiom for this 开发者_JS百科exist already? Two obvious benefits would be parameter information in IDEs and not having to check if all hash keys are supplied.
What I want to avoid is:
puts "Setting first_name to #{first_name}"
puts "Setting last_name to #{last_name}"
# and so on
If you set no other local variables inside the method, local_variables
will give you a list of the method's parameter names (if you do set other variables you can just call local_variables
first thing and remember the result). So you can do what you want with local_variables
+eval
:
class Automator
def fill_specific_form(first_name, last_name)
local_variables.each do |var|
puts "Setting #{var} to #{eval var.to_s}"
end
end
end
Automator.new().fill_specific_form("Mads", "Mobaek")
Be however advised that this is pure evil.
And at least for your example
puts "Setting first_name to #{first_name}"
puts "Setting last_name to #{last_name}"
seems much more sensible.
You could also do fields = {:first_name => first_name, :last_name => last_name}
at the beginning of the method and then go with your fields.each_pair
code.
I don't quite understand. Do you want to receive all parameters within a single array?
def fill_specific_form *args
#Process args
end
To reflect on a method's (or Proc
's) parameters, you can use Proc#parameters
, Method#parameters
or UnboundMethod#parameters
:
->(m1, o1=nil, *s, m2, &b){}.parameters
# => [[:req, :m1], [:opt, :o1], [:rest, :s], [:req, :m2], [:block, :b]]
However, in your case, I don't see why you need reflection, since you already know the names of the parameters anyway.
精彩评论