In tealeaf week 3, introduce to HTTP.

The most important thing is that, HTTP is stateless.

What’s the influnce by this property? Showing this by Sinatra.

first, follow Sinatra intro to run basic function:

then try this code:

main.rb
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require 'sinatra'

before do
  @name = 'Guest'
end

get '/' do
  erb :home
end

post '/set_name' do
  @name = 'tealeaf'
  redirect '/'
end

and this will show a button, click the button will invoke a post request back to set_name in main.rb:

home.erb
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<h4>hi~ <%= @name %> </h4>

<form action="/set_name" method="post">
  <input class="btn" type="submit" name="name">
</form>

OK, then what will @name show in home.erb after click button??

It shows Guest, not tealeaf. Why?

The key point is: when 2 redirect to 3, it’s a new request, instance variable like @name will be deleted after redirect, then create a new one.

That’s why @name still shows Guest.

How about this way:

main.rb
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require 'sinatra'

before do
  @name = 'Guest'
end

get '/' do
  erb :home
end

post '/set_name' do
  @name = 'tealeaf'
  erb :home
end

Now using erb to embeded home.erb into the same request(‘/set_name’). Then you’ll see @name shows tealeaf!!

This experience shows me how HTTP is stateless.

And how web developers make it like stateness is a long way to go.