从Rails中的Model对象中调用访问器方法

Question

I have the following method in my model

def reset_review_status
   needs_review = true
   save
end

There is an attribute on the model called needs_review, however when I debug it, it saves it as a new variable. If I do self.needs_review=true , it works fine. I have no attr_accessible clause, although I do have one accepts_nested_attributes_for.

Any thoughts on why this might be happening?

Answer 1

When you define an attribute in ActiveRecord, the following methods are available

# gets the value for needs_review
def needs_review
end

# sets the value for needs_review
def needs_review=(value)
end

You can call the setter using

needs_review = "hello"

but this is the same way you set a variable. When you call the statement within a method, Ruby gives higher precedence to variables assignment, thus a variable with that name will be created.

def one
# variable needs_review created with value foo
needs_review = "foo"
needs_review
end

one
# => returns the value of the variable

def two
needs_review
end

two
# => returns the value of the method needs_review
# because no variable needs_review exists in the context
# of the method

As a rule of thumb:

1. always use self.method_name = when you want to call the setter within a method
2. optionally use self.method_name when a local variable with the same name exists in the context