Ruby on Rails 2.3.8：测试：实例变量Nil，当在类顶部声明时？

Question

So.. here is the top of my unit test file.

class ObjectTest < ActiveSupport::TestCase
  @user = -1

the test that fails (also the first one to use @user)

test "for detection of first content" do
  puts "+++++++++++++++++++++++++++++ #{@user.name}"

And this is the error I get

NoMethodError: undefined method `name' for nil:NilClass

Now, I know that a number can't have any attributes like .name.. but I'm trying to solve a problem unrelated to trying to get the name of integers. The problem is that instance variable defined anywhere in my test file instantly turn to nil when na test begins -- as you can, the actual content of the test doesn't matter, the data inside @user is vanishing somehow. =\\

Answer 1

Class instance variables are a little odd, and I've not used them that much, but if I grok them correctly, they exist on the class itself and can only be accessed with the @ symbol in class methods - so you will have to access @user as ObjectTest.user or self.class.user when you are in instance methods, otherwise Ruby will look for the instance instance variable inside of instance methods. In other words, in a class function, you can refer to @user , but in an instance function, Ruby is looking for the @user variable on the instance . here is a page that seems to demonstrate this behavior.

Since class variables (eg @@user ) use a completely different syntax, they should not show this scope-colliding behavior - you can use @@user in both class and instance methods.