I have the following code:
for attribute in site.device_attributes device.attribute end
where I would like the code to substitute the value of "attribute" for the method name.
I have tried device."#{attribute}"
and various permutations.
Is this completely impossible? Am I missing something?
I have considered overriding method_missing, but I can't figure out how that would actually help me when my problem is that I need to call an "unknown" method.
Ruby allows method names and other identifiers to contain such characters.) Method names may contain letters, numbers, an _ (underscore or low line) or a character with the eight bit set. Method names may end with a ! (bang or exclamation mark), a ? (question mark) or = equals sign.
What's an instance variable? In the Ruby programming language, an instance variable is a type of variable which starts with an @ symbol. An instance variable is used as part of Object-Oriented Programming (OOP) to give objects their own private space to store data.
A variable itself is not an object. "A variable in Ruby is just a label for a container. A variable could contain almost anything - a string, an array, a hash.
You can use #send method to call object's method by method's name:
object.send(:foo) # same as object.foo
You can pass arguments with to invoked method:
object.send(:foo, 1, "bar", 1.23) # same as object.foo(1, "bar", 1.23)
So, if you have attribute name in variable "attribute" you can read object's attribute with
object.send(attribute.to_sym)
and write attribute's value with
object.send("#{attribute}=".to_sym, value)
In Ruby 1.8.6 #send method can execute any object's method regardless of its visibility (you can e.g. call private methods). This is subject to change in future versions of Ruby and you shouldn't rely on it. To execute private methods, use #instance_eval:
object.instance_eval { # code as block, can reference variables in current scope } # or object.instance_eval <<-CODE # code as string, can generate any code text CODE
You can use public_send
to call methods with regard to visibility rules.
object.public_send :public_foo # ok object.public_send :private_bar # exception
The "send" method should do what you're looking for:
object = "upcase me!" method = "upcase" object.send(method.to_sym) # => "UPCASE ME!"
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