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Ruby Gems

Ruby Gems

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • RubyGems 0:08
    • What are RubyGems?
  • 0:44
    • How RubyGems are used
    • Java's jar utility
    • Unix/Linux's tar utility
  • What is a Gem? 3:16
    • Definition of Gem
    • Version
    • Date
    • Author
    • Description
  • What Are the Uses? 4:18
    • Uses for Gems
  • Installation 5:06
    • How to install RubyGems
  • Updating to the Latest Ruby Gems 5:54
  • Testing 6:22
    • Example
  • Installing Rake 7:24
    • Example
  • Verifying 9:22
    • Example
  • Structure 10:56
    • gem.gemspec
  • Specification 13:40
    • What is in the gem?
    • Who made it?
    • Update gem version
    • Example
  • Create Our First Gem 17:20
    • Steps involved
    • RubyGems Guides
    • Example
    • Steps Review
  • Create Our First Gem (Cont.) 23:08
    • Building the gem
    • Example
    • Installing the gem
    • Run it
    • Publish it
  • Get Some Gems! 25:06
    • rake
    • rails
    • fastercsv
    • koala

Transcription: Ruby Gems

Welcome back to

Today's lesson will be on Ruby Gems.0002

What are Ruby Gems? It's a package utility for Ruby--think of it as--you have different packages, like tar, zip, compressed files--well, the package utility for Ruby...that is what Ruby Gems does.0005

It has the exact same feature for that.0024

Let's go ahead and look at, so we can see more of what they are, and get a good feel of how it is being used.0026

This is the site.0039

There are tons of downloads here--865 million.0044

There are a lot of different Gems.0050

You can use these Gems in your projects; you can put them into your project and use them for your own codes, so you're not reinventing the wheel.0051

You're using this code for your own benefit, and you can concentrate on the stuff that matters.0063

There are some links here: there's one that says "Learn"; it will teach you about Ruby Gems by clicking that.0069

There is a share button, and there is "Install RubyGems"0078

You can browse the guides--it's explanations, tutorials, references...and Gem specifications.0083

We are going to go over all this stuff; we want to make sure you get used to these RubyGems.0090

This is a very popular thing in Ruby.0095

Here update your Gems...gem update can build your Gem using gemspec...and you can push your Gem to this website.0098

It does require you signing up for an account, but then you can create your own Gem, and you push it, and it will be out there for everyone to use it.0109

Notice, they also give you a list of what the most-downloaded Gems today were, what was just updated, and some of the newer Gems out there.0116

Before we go any further, make sure, at the top right, you do sign up.0131

Make sure you sign up for the site; then you can keep track of the Gems you've downloaded and the ones you are pushing--uploading.0135

Notice, here are all the "Learn" buttons...we will go through them later, but let's go back to our slide now.0144

Ruby Gems has their own packages for different languages.0161

I put here Java JAR--that is Java's version of Ruby Gems--the JAR function.0168

And UNIX and Linux have the tar utility.0178

These are just a couple of them; the other languages do have their own, also.0182

These are more of the common ones I've seen.0191

So, what is a Gem? Like I said, it's a package--we've already gone over that--and it contains all the necessary files and information to run on this system.0195

In these Gems themselves, they will have version information.0206

It will also have the date it was created.0219

Author is quite common; the description of what the Gem is; and there are more pieces of information, too.0227

What is the use of these Gems?0255

Extend or modify functionality within your Ruby application.0258

Avoid duplication: you don't want to be creating code that someone else has already created; why don't you go with a Ruby Gem...find that piece of code, see if someone has already developed it and just pull that in.0267

You can make their Gem better--be a contributor and help out.0280

Again, stop reinventing the wheel.0284

Fourth, follow Ruby's open source foundation--strong open source foundation--help contribute.0288

Installation: we are going to go over how to actually install Ruby Gems.0303

If you have already looked at our installation lesson, and you have RVM set up, it's already set up; so you can actually skip this and go on to the next lesson.0310

But this is still good information, so if you want, you can look at this, too.0322

Otherwise, you go back to that site that we showed you, download the source--it's going to come as tar/gzip file--uncompress that, go into the directory, and just do ruby setup.rb.0325

That will get you set up with RubyGems.0344

Now, how do you know if you have it installed?0348

First, to update to the latest RubyGems, you just run gem update --system.0352

This gem command will actually be existing on your system after it's installed.0361

So, you could do gem --version, and it will show you the version of it.0366

Here we go: we can run through some of the commands now, too.0371

So, if I do gem -v, it gives me the version, and when I do gem --version, it also comes up; when I do gem in this, I get a lot of usage information about it, too.0395

And this is the RubyGem sophisticated package manager.0410

I see this with gem--and gem help will actually show you the exact same information.0423

And gem --version is just to verify that you installed their correct one.0437

Now, we can have an example of setting up a Gem.0443

One that you should already have it, if you don't already, is the Rake Gem.0448

That's gem install rake.0452

We can go to the site and take a look at that.0457

Right here, in this search box, I'm going to put "rake."0466

It gives me a lot of Gems that have used Rake for their dependencies, and they add features to it, but we just want the main one.0473

I'm going to get the Rake one--Rake

It has the download link, documentations and can subscribe to follow the Gem and track what progress is being made...0491

It says that the total number of downloads was quite a lot, in the number for this version.0501

You can actually see the Gem following the version.0508

It doesn't really show you anything about how to install it, but it's so easy--it's just gem install rake; it's right there.0515

It's already installed, but we can actually go ahead and try it now; let's see what information it gives us.0526

It should say it has already been set up, but...0532

It's a very simple command--gem install rake--and it will show some information there.0535

While that's running, let's keep going, though.0549

So, verifying the Gems--you can see what Gems are installed with Gem List.0564

We should actually do that; let's take a look at that and make sure it's set up.0572

For this task, look for the Rake and the version number--there's a rake command where we can verify that.0577

Then, just run rake --version.0587

I'm going to quit out of this; it's going kind of slow, but let's check.0595

And there you go--it has already been installed: Rake

Rake --version...there it's already set up; I'll just do rake and see if it gives me some usage information.0607

There you go--if I have my rakefile on here, I can go ahead and run it.0615

That's good...let's see if there's a rake help here...there is a rake help file, too, to show you how it's used.0620

rake...and included the specified, explicit filename with -f.0635

The options are below.0640

The next part is: we want to go over the structure to create your Ruby Gem.0650

It's a very common structure that is used, and it's very standard, so please follow it.0658

If you do add extra common things to it, those will just be additions; so this structure should be followed.0667

First, you also have...whatever Gem you have--the directory that holds everything.0674

It doesn't matter what name you give it.0684

What is really important is this gem.gemspec file, because that is going to be the specifications that everything is set in.0687

First, what happens is all your code is going to go to this Lib directory, which is a subdirectory to Gem.0696

You don't have to specify your file as gem.code; it could be whatever name you give it.0705

As long as your specifications say that file is included, it will include that file.0713

And we are going to go over the specs, so you can take a look at them.0720

Test is for unit testing; it's recommended to use it as you're doing your first one.0724

You're probably still learning it, so...0732

For our uses, we're not going to do any unit tests right now.0739

Readme--very self-explanatory: if I get your Gem, I look at the sourcecode, I want to look at your readme to see how I set it up, a description, installation...any tips or common things I should know.0747

Your rakefile--if there are any tasks that are common that you created to run your Gem--anything I need to load--you can specify in your rakefile.0764

This is also optional.0776

So, this test and this rakefile, and even this readme, these things are all optional, but recommended.0778

And the last one is the gem.gemspec file.0796

Depending on the name you give your Gem, this will change, but whatever name you give it, that should be the name that is placed here and even in your code.0799

OK, to the specifications: What is in the Gem?0819

You can include the name of it, a description of what it is, the version, who made it--include your author information...the developer...0824

And, as you continue to build the specification, you want to continue to update it and update the version for it.0839

Let's go ahead and do that now--let's create our first Gem!--how about that?0848

Let's start with the specifications.0853

I actually want to...get another code base...OK, so we have our structure in a lib directory.0862

The first thing we want to do is create the spec file.0873 the first thing is you want to create your Gem specifications.0878

The first thing I'm going to put is the actual name of this Gem.0897

I'm just going to call it Educator.0900

And then, I'm going to specify the version; for this version, I'm going to start very, very low.0905

Here is the date we are using.0919

Let's just make this like a hello world app--how about that.0937

Authors--for authors you can specify multiple--I'm just going to specify myself, but you can continue to add more to the list.0943

Now, for s.files, this is very important that you include all of your files to this directory.0964

So this one--we're only going to use one file in this.0974

Too big...and the homepage...they will actually give you a place to load your Gems; in this case, it's called Educator.0978

I'm going to show you the path it is being uploaded to, so you can see--you could even download it yourself.0989

OK--we have our Gem specification done.0997

We have more than enough information for it.1000

Really, you need to require the version, author, and the name, because those are needed for the Gem to be generated out.1007

OK, we've saved that; if you look in there, we have our educator.gemspec.1021

Let's go back to the slide now.1029

We have our specification done; next, let's look at the guide to creating our first Gem.1034

OK, I have it here.1050

Well, we already know what a Gem is; we want to make our own now.1054

Introduction...our first gem...required files...executables...tests...documenting your code...1063

Even here, you will notice they are fairly simple.1074

There is structure; they have a .gemspec file; the code is in the lib directory.1079

It even says, reading through this file, "Package is placed within the lib directory"; once your Gem is loaded, you just do require, and it will run it.1087

They have their specifications here.1100

When you have created a gemspec, you can build your Gem and install it.1104

Let's go ahead and try it out.1110

I want to actually go in the directory to create it.1121

Let's go back to the slide we know all the tasks for it--that is our next thing; we need to build it.1130

After we implement all the code--this includes developing the code for it--then we can install it, run it, and publish it.1142

Our main thing will be this build step, where we have to create the code.1159

After that, all these are things that are more simple to do.1167

Let's go to work on our first step to build this Gem.1174

Since we are calling it Educator, it's going to actually be called educator.gemspec.1179

Let's get some code for that now.1196

Make sure we're in the right let's touch educator.rb, class Educator, and we'll have just a very simple hello world.1200

OK, excellent: so we have our code file; we have our .gemspec.1232

Now, let's try to build it.1238

It says no description was specified; but it still built the Gem.1245

Warning...and we didn't include a description, so let's do that.1253

Let's try it again now...excellent: we don't get the warning.1271

Now, we go to the file itself: Educator-0.0.1.gem.1275

The next thing is, we want to actually install this gem now that we've done the build step.1286

So, what this command does: gem install educator-0.0.1; it's going to install this Gem into my RubyGems.1295

I can actually use this Gem in my code.1305

There you go: it's installed--I have my Gem installed, I have some documentation--I didn't actually set up any, but we've gone through the RDoc lesson, so I'll let you guys do that.1310

So, now I can just go to require 'educator'--it says "true"--then I specify the actual code, and there you go: it prints "hello world."1322

We've built it, installed it, and now we can publish it to the world if we wanted to.1332

We went through this step; gem install rubygem-0.0.1--this version will change, depending on what you put in the .gemspec, and this will also change.1352

Again, to run it, since it's already in your Gem directory, you can require it--as simple as that: just putting the name of it in.1371

The next step would be, "Hey, I have this great code piece; I want to publish it to the world! I'm going to help other people use it; I already developed it--why don't I help others and maybe, if I have some feature I would like to have with it, but I don't have time, maybe someone else could work on it, too!"1385

This step is to publish it.1403

To do this, you would sign up on, and then they have a command to help you publish it.1407

It's back on their's exactly like the slide--you run this curl command, it goes to this URL--you will specify a username when you sign up for your account, and now it's going to ask you for that password that you created with the user.1417

Once you do that, you just run gem push, and it will actually push it to the website, and your Gem will be up.1448

Notice here, you are doing this curl command; change this to your name; and then this URL will stay the same, and you just put in this and the curl with the Gem; you put in your credentials, and you put your password here.1456

Then, all you have to do is just run this gem push, and it will push the Gem to, and you will see it by the message: it will say, "Successfully registered"--your Ruby Gem is online now.1481

Other than that, I would say just start looking at those Gems and downloading some.1505

We've looked at Rake; another popular one is the Rails Gem; FasterCSV is a Gem you can use to parse CSV files, and it's quite popular, and it does the job really well.1512

Then this one called Koala will allow you to interact with the Facebook API and start using Open Graph.1531

So, that is the lesson today at

You just learned RubyGems.1545

Join us again for the next lesson!1548