Ruby Local Variable Is Undefined

Ruby local variable is undefined

In Ruby local variables only accessible in the scope that they are defined. Whenever you enter/leave a Class, a Module or a Method definiton your scope changes in Ruby.

For instance :

v1 = 1

class MyClass # SCOPE GATE: entering class
  v2 = 2
  local_variables # => ["v2"]

  def my_method # SCOPE GATE: entering def
    v3 = 3
    local_variables  # => ["v3"]
  end # SCOPE GATE: leaving def

  local_variables # => ["v2"]
end # SCOPE GATE: leaving class

These entering and leaving points are called Scope Gates. Since you enter through Scope Gate via method definition you cannot access your local_var inside hello method.

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You can use Scope Flattening concept the pass your variable through these gates.

For instance instead of using def for defining your method you can use Module#define_method.

local_var = "Hello"

define_method :hello do
  puts local_var
end

In the same way you can define your classes via Class#New so that your scope does not change when you pass through class definition.

local_var = 'test'

MyClass = Class.new do
  puts local_var #valid
end

instead of

class MyClass
  puts local_var #invalid
end

In the same way you should use Module#New if you want to pass your local variables through Module gates.

Example is taken from Metaprogramming Ruby

Rails 6 - undefined local variable when passed to a partial but it is defined when I put a debugger in the erb file

you should be using local_assigns[:discount_rule] to access the local variables.

one could use collection: @programs.discount_rules, as: :discount_rule as well and call discount_rule in the view.

At the same time make sure that the data is not nil in your controller and that you are able to print the required attribute like name before passing it to partial with something like .each do |instance| p.name

Ruby: undefined local variable (NameError) -- but it is defined

A local variable's scope cannot cross a method definition. positions that is assigned outside of the method definition is not visible from within the method definition.

To make it visible, you can make it an instance variable, class variable, global variable, or constant, for example. Or, you can pass it as an argument to the method.

Ruby on Rails undefined local variable or method in console

There are 2 things that could be happening. First, you meant to list Article.all, referencing the class. Second, you're referencing article.all as a array, in which case it hasn't been defined as such in your code.

Also, please don't post images of code. Just copy/paste and use the code formatting tools. It really helps us understand what is going on.

Also, it helps to give as much background as possible, meaning what the code is supposed to do, why you're doing it, etc. The more thorough you are, the more helpful we can be.

Undefined local variable or method `user' - how do I reference user?

class PagesController < ApplicationController
  def index
    @users = User.all
  end

...

rename contacts.html.erb to index.html.erb

index.html.erb

<table class='table table-condensed'>
  <thead>
    <tr>
      <th>Email</th>
      <th>Action</th>
    </tr>
  </thead>
  <tbody>
    <%= render partial: 'contact', collection: @users, as: :user %>
  </tbody>
</table>

Ruby - undefined local variable or method `_1'

You're probably running an older version of ruby - the numbered parameters for blocks have been available in ruby since 2.7 - see https://www.bigbinary.com/blog/ruby-2-7-introduces-numbered-parameters-as-default-block-parameters

You can make it work on older version by using

p result.scan(/\w+=\w+/)
        .map { |s| s.split("=") }
        .to_h

undefined local variable or method ruby

In File 'F' should be in capital. That's the mistake

File.open("text.txt").each { |line| puts line }

Also make sure "text.txt" is in same directory as you ruby script, else provide absolute path like File.open("absolute/path/to/text.txt")

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