I have a Ruby object User, which has a :first_name member variable. I would like to be able to access that variable with a string.
So if I have a user called u:
u.'first_name' should be equivalent to u.first_name
How could I use reflection to get u.first_name through the string, which is passed in as a variable?
I think what you mean with "member variable", is that you have a model that has an attribute called first_name. If so, then you can access that attribute as you'd do in a "plain" ("plain" because the question is focused to Rails) Ruby class:
class Foo
attr_accessor :name
def initialize(name)
@name = name
end
end
foo = Foo.new('bar')
p foo.instance_variables # [:@name]
p foo.instance_variable_get('@name') # "bar"
The most idiomatic way to get dynamically an instance variable is using instance_variable_get, but you can also use send, or better using __send__, or even better in your case using public_send:
foo = Foo.new('bar')
p foo.instance_variables # [:@name]
p foo.instance_variable_get('@name') # "bar"
p foo.send('name') # "bar"
p foo.public_send('name') # "bar"
The way Rails handles your models and attributes is almost the same (NOTE: opened to edition). By instantiating one of your models, you can get the attribute you need:
user = User.first
user.email # [email protected]
user.public_send('email') # [email protected]
self,nil,true, andfalse.u.first_nameis a message send, it has nothing to do with variables.