First Rails application - Step-by-Step Execution

Concept Flow - First Rails application

Run 'rails new app_name'

↓

Rails creates folder structure

↓

Navigate to app folder

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Run 'rails server'

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Server starts and listens

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Open browser at localhost:3000

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Rails serves default welcome page

This flow shows how to create a new Rails app, start the server, and see the default page in the browser.

Execution Sample

Ruby on Rails

rails new myapp
cd myapp
rails server

Creates a new Rails app named 'myapp', moves into its folder, and starts the Rails server.

Execution Table

Step	Command/Action	System Response	Result
1	rails new myapp	Creates app folder and files	Folder 'myapp' with Rails structure created
2	cd myapp	Changes directory	Current folder is 'myapp'
3	rails server	Starts Rails server	Server listens on http://localhost:3000
4	Open browser at http://localhost:3000	Server responds	Default Rails welcome page shown
5	Stop server (Ctrl+C)	Server stops	No longer listening on port 3000

💡 Server stops when user interrupts; app folder and files remain for development.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
Current Directory	User home	myapp created but not entered	myapp	myapp	myapp	myapp
Rails Server Status	Stopped	Stopped	Stopped	Running	Running	Stopped
Browser Page	None	None	None	None	Rails Welcome Page	None

Key Moments - 3 Insights

Why do we need to run 'cd myapp' after creating the app?

Because 'rails new' creates the app folder but does not move you inside it. You must 'cd' to run commands like 'rails server' inside the app.

What happens if you open the browser before starting the server?

The browser will not connect because the Rails server is not running yet. See step 4 in execution_table where the server must be running first.

Why does the default page show a welcome message?

Rails includes a default welcome page to confirm the server works. This is shown at step 4 when accessing localhost:3000.

Visual Quiz - 3 Questions

Look at the execution_table, what is the system response after running 'rails new myapp'?

A Starts Rails server

B Creates app folder and files

C Changes directory

D Server stops

💡 Hint

Check step 1 in the execution_table for the response to 'rails new myapp'.

At which step does the Rails server start running?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look at the 'Rails Server Status' in variable_tracker and the 'System Response' in execution_table.

If you skip 'cd myapp' and run 'rails server' from the home folder, what happens?

A Error because no Rails app found

B Server starts normally

C Creates new app automatically

D Shows default welcome page

💡 Hint

Refer to key_moments about why 'cd myapp' is needed before running 'rails server'.

Concept Snapshot

rails new app_name  # creates new app folder and files
cd app_name          # move into app folder
rails server         # start Rails server
Open browser at localhost:3000 to see default welcome page
Stop server with Ctrl+C
This sets up your first Rails app ready for development.

Full Transcript

To create your first Rails application, you start by running 'rails new' with your app name. This command creates a folder with all necessary files. Next, you must change directory into the new app folder using 'cd'. Then, start the Rails server with 'rails server'. The server listens on localhost port 3000. Opening your browser to this address shows the default Rails welcome page, confirming the server runs correctly. When finished, stop the server with Ctrl+C. This process sets up your first Rails app ready for further development.