How is it different to declare a variable with and without "@" in Ruby?

Question

What is the difference between these two possibilities?

//com @
@post = Post.find(params[:id])

//sem @
post = Post.find(params[:id])

Normally in controllers is used with @, but in office each views is usually used without the @, for example.

There are differences in performance?

Answer 1

the variables they have @ are instance variables in the current object scope. the variables without @ are local variables in the current object scope.

In the specific case of Rails, the variables with @ used in the controllers are available to be used "inside" the views.

To the each which was quoted follows the example below:

@posts.each do |post|
  <faz alguma coisa com 'post' aqui>
end

in this code snippet, the variable post is local to the scope of the block in which it was defined, so it exists only within the block do |post| ... end

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To better understand the differences between the types of variables, classes and objects, take a look at this link http://aprendaaprogramar.rubyonrails.com.br/index.rb?Chapter=09.

About the each, look here http://aprendaaprogramar.rubyonrails.com.br/index.rb?Chapter=07

Answer 2

It’s like Bruno said the variables without the @ can only be accessed within the scope in which it was created, in which case if you create in the controller, you cannot access the variable in the view.