A History Lesson

• Imagine being a villager living in Melanesia, circa 1940.

image source

A history lesson

• You're living a lifestyle that has largely remained unchanged for thousands of years.
• Fishing and gathering are primarily how you make a living. Things are tight, but generally good.
• Sometimes there are violent clashes with neighboring tribes.
• Any illness or serious injury usually results in death.

A history lesson

• One day, something strange happens.
• Directly above, around, and in your village, the largest war ever fought by humans takes place — World War II.
• The most technologically advanced nations in the world start building bases on your island.
• Soldiers arrive in planes, gliding down and landing on runways, and take up residence in the bases. But they don't fish or gather.
• To supply these bases, planes would airdrop cargo containing food, weapons, medicine, and other supplies.

A history lesson

• This cargo is unlike anything you've ever seen.
• The food is unbelievably nutritious. One package could feed your family for a month.
• The weapons would make your tribe invincible.
• The medicines are miraculous life savers.

A history lesson

• Then, one day, the conflict ends.
• The soldiers abandon their bases and runways. They take their planes and leave.
• The cargo stops being airdropped.
• People start dying from trivial injuries again.
• What do we need to do to get access to similarly nutritious food and effective medicine?

A history lesson

• Well, back when the airdrops were coming, there were planes sitting by the runways.
• Now there are no planes.
• Maybe it's the presence of planes that causes the cargo to come?

A history lesson

• Believing cargo to be blessings from the gods, "cargo cults" formed.
• They would build planes out of wood, uniforms out of straw, and perform the rituals that they had observed the soldiers performing.
• Some of these cults lasted for decades.

A history lesson

• Why do you think I'm telling this story?

Copy-paste

• Copy-pasting is a double-edged sword.
• It's great for avoiding typos, e.g.,
  • access tokens
  • URLs
• However, when you copy-paste code from one context to another, it will not work unmodified.
• The different context is, by definition, solving a different problem — or it wouldn't exist.

Copy-paste

• The different context won't have the same params, instance variables, etc.
• If you don't understand why and how the code was working in the original context, copy-pasting it into your new and different context will just introduce lots of bugs and make it harder to make progress.
• This is known as "cargo-cult programming".

Copy-paste

• Even if it would work unmodified, you should still type it out when you're a beginner. Typing out code is essential for developing your own muscle memory.
• With experience, you will develop intuition for when it's okay to copy-paste and when it isn't.
• For now, when in doubt, err on the side of typing out code.

Rubber Duck Debugging

• When you get stuck or face a problem that you can't figure out, try talking through the problem as if you're explaining it to someone else.
• This process can help clarify the issue and lead to a solution.
• This is called "rubber ducking".
• The name originates from a story where a programmer would carry around a rubber duck and debug their code by explaining it, line-by-line, to the duck.

Work in tiny little steps

• When you're solving a problem, don't try to jump all the way to the end in one go.
• What is a series of small steps that will get you to your goal?
• Figuring out the tiny steps to get from the starting point to the solution is engineering.

Try pseudocode first

• Try writing out your steps in comments

def show
  # get id from params
  # use id to get record from db
  # make record accessible using instance variable '@'
  # render template
end

Make the Invisible Visible

• Start small. What's the first thing you can print?

puts "My var here: #{my_var}"

• Print things constantly to verify that each step did what you thought it did.

Make the Invisible Visible

• Make instance variables and embed them in the view. You can delete them later.

<%= @my_variable.inspect %>

Make the Invisible Visible

• If there's an error page, use the interactive console to display the contents of params, variables, and to experiment with potential solutions for the error.

Make the Invisible Visible

• --Read-- the server log. (Clear it often ⌘+k)

Started GET "/directors" for 130.126.255.106 at 2023-05-04 21:50:42 +0000
   (0.2ms)  SELECT sqlite_version(-)
Processing by DirectorsController#index as HTML
  Rendering director_templates/index.html.erb within layouts/application
  Director Load (0.6ms)  SELECT "directors".- FROM "directors" ORDER BY "directors"."created_at" DESC
  ↳ app/views/director_templates/index.html.erb:29
  Rendered director_templates/index.html.erb within layouts/application (Duration: 7.6ms | Allocations: 5127)
Completed 200 OK in 13ms (Views: 9.7ms | ActiveRecord: 1.5ms | Allocations: 7634)

Use rails console

rails c to enter a repl

Try debugger

• Add debugger anywhere in your code to stop execution and inspect variables
  • c to continue
  • n to execute next line

def show
  my_id = params.fetch("id")
  debugger
  my_record = MyModel.where({ :id => my_id }).at(0)
  render({ :template => "my_views/show.html.erb" })

• it even works in html.erb files!
  • <% debugger %>

Restart / Refresh

• Try restarting your server or refreshing the page
• Configuration and settings are only set on server boot
• Your views are only reloaded when refreshing the page

Limit your variables

• When trying to pass rake grade tests, make sure your development environment matches the tests

1. rails db:drop # drop your database
2. rails db:migrate # spin up a new database
3. Use rails console to add ONLY the records in the test
4. Then follow the test step-by-step

Limit your variables

describe "/movies/[ID]" do
  it "displays the title of the movie", :points => 1 do

    movie = Movie.new
    movie.title = "Flubber"
    movie.save

    visit "/movies/#{movie.id}"

    expect(page).to have_content(movie.title)
  end
end

Use ask.firstdraft.com

• It's great to have a conversation to help talk through a problem
• Remember, AI can be totally wrong
• It's best to not just copy paste AI output

"How to Solve It"

1. First, you have to understand the problem.
2. After understanding, make a plan.
3. Carry out the plan.
4. Look back on your work. How could it be better?

Understand the problem

Try asking yourself (and each other) the following questions:

• What are you asked to accomplish?
• Can you restate the problem in your own words?
• Can you think of a picture or a diagram that might help you understand the problem?
• Is there enough information to enable you to find a solution?
• Do you understand all the words used in stating the problem?
• Do you need to ask a question to get the answer?

Questions? Thoughts?