> For the complete documentation index, see [llms.txt](https://certil-remy.gitbook.io/learn/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://certil-remy.gitbook.io/learn/ruby/untitled-8.md).

# Method-scope-lab

## Objectives

1. Define a method that takes in an argument and pass a variable in as that argument.
2. Understand that a variable defined inside a method cannot be used outside of that method.

## Instructions

### Part I: Passing a Variable Into a Method

Open up `lib/catch_phrase.rb`. You should see the following method:

```
def catch_phrase
  puts phrase
end
```

Note that the method is trying to `puts` out a variable called `phrase`.

Let's take a look at the test for this method in `spec/catch_phrase_spec.rb`:

```
describe "#catch_phrase" do
  it "puts out a catch phrase" do
    phrase = "It's-a me, Mario!"
    expect{catch_phrase}.to output("It's-a me, Mario!\n").to_stdout
  end
end
```

Go ahead and run the test for this method only by typing `rspec spec/catch_phrase_spec.rb` into your terminal in the directory of this lab. You should see the following error:

```
NameError:
  undefined local variable or method `phrase' for #<RSpec::ExampleGroups::CatchPhrase:0x007f87b9cf04c0>
```

This error is occurring because the code inside the `#catch_phrase` method is trying to use the `phrase` variable **but** it's not present inside the *scope* of the `#catch_phrase` method. **It is out of scope.** Let's fix it!

We need to pass `phrase` into our `#catch_phrase` as an argument. Let's do it:

1. Re-define the `#catch_phrase` method to take in an argument of a phrase.
2. Change the test in `spec/catch_phrase_spec.rb` to match the following:

```
require "spec_helper"
describe "#catch_phrase" do
  it "puts out a catch phrase" do
    phrase = "It's-a me, Mario!"
    expect{catch_phrase(phrase)}.to output("It's-a me, Mario!\n").to_stdout
  end
end
```

### Part II: Understanding Method Scope

Open up `lib/rescue_princess_peach.rb` and take a look at the following method:

```
def rescue_princess_peach
  status = "rescued"
  puts "Hooray! Mario has rescued Princess Peach."
end
```

Notice that the body of this method is setting a variable, `status` equal to a value of `"rescued"`. Do you think we will be able to access this variable outside of the method? Let's find out!

1 . Un-comment the following lines in your `lib/rescue_princess_peach.rb` file:

```
rescue_princess_peach
puts status
```

2 . Run the file with `ruby lib/rescue_princess_peach.rb` in your terminal. You should see the following:

```
Hooray! Mario has rescued Princess Peach.
lib/rescue_princess_peach.rb:12:in `<main>': undefined local variable or method `status' for main:Object (NameError)
```

We are getting a `NameError` because `status` is undefined. Wait a minute, you might be wondering. Didn't we define `status` inside the `#rescue_princess_peach` method? We did, but **variables defined inside a method are not available outside of that method**. They are only available within the `scope` of that method.

**Go back and comment out lines 11 and 12 of `rescue_princess_peach.rb`.**

Run the test suite and you'll see that we are passing all of our tests. If you open up the `spec/rescue_princess_peach_spec.rb` file, you'll see the following test:

```
require "spec_helper"

describe "#rescue_princess_peach" do
  it "outputs a message and sets a variable, status, that is not available outside of this method" do
    expect{rescue_princess_peach}.to output("Hooray! Mario has rescued Princess Peach.\n").to_stdout
    expect{puts status}.to raise_error(NameError)
  end
end
```

Notice the last expectation of our test: `expect{puts status}.to raise_error(NameError)`. We expect any attempt to use the `status` variable to be met with a `NameError`. Our program, outside of the `#rescue_princess_peach`method, just doesn't know what it is.

View [Method Scope Lab](https://github.com/learn-co-curriculum/method-scope-lab) on Learn.co and start learning to code for free.


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