Breaking the example down

The classic example:


Let's start at the first line - (require 'sinatra') - what does this actually do?
After a quick lookup the require keyword will take the string you give it, which must be a path to a file e.g. './childDir/blah.rb' or a shortened name 'blah'.

Let's experiment for a second...

/*Create a test file (to test the require)... */
mkdir experiments
cd experiments/
vi require_experiment.rb
i /*for insert*/
require './test/hello.rb'
ESC
:wq

mkdir test
vi test/hello.rb
i
puts 'hello world'
ESC
:wq

Now run the file with ruby require_experiment.rb
and we get:
>> hello world

OK... so now we know that when we require something it runs the code in it.

How about if we leave off '.rb' in the require?
we get:
>> hello world

what if we reference a class from the parent file, and then try to use it in another referenced file??? will that work?






OK... so I get an error:

:29:in `require': no such file to load -- file_with_hello_class (LoadError)

OK... so that's interesting - we can't just reference the file with a name, we need to put "require './file_with_hello_class'" in order for ruby to find it.

Once we correct the require statement - it actually runs!:
>> hello

So... even though we've loaded file_with_hello_class from require_experiment, the hello file can now see the class that was declared in file_with_hello_class.

Another thing we can check is what happens if we run the file from another directory?

cd ..
ruby experiment/require_experiment.rb

>> `require': no such file to load -- ./file_with_hello_class (LoadError)

So the way we've got things setup now... we can't just run the file from anywhere.

---

What happens if we do a require with a short name e.g. "require 'sinatra'"... well after looking it up, it appears that ruby will look in the directories stored in the global $LOAD_PATH variable for the mentioned file.

Put a 'puts $LOAD_PATH' in your ruby file, run it and try it out OR try it from irb.

There's a problems we came up against with require, where it didn't find a relative file unless we put './' in front of it, and also when we then moved to a parent directory and tried running the file it didn't work. I'll take a look at this in the next post...

Sinatra on Ruby

Let's tell you what I know, and try to explain what I don't...

To Get started with Sinatra you go to sinatrarb.com/intro.html and follow the example. It provides the classic 5 lines needed to get up and running.



OK... That's great, but how about a real application? what about testing, authentication, uploading images and performing ajax calls....

The problem for me at least is that I'm relatively new to Ruby and sinatra, and while it's easy enough to create an app that works, I'd like to get into the harder stuff.  That's what this blog is about.