Difference between revisions of "Ruby/C3/for-and-each-Looping-Statements/English-timed"
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Revision as of 17:09, 30 December 2015
| Time | Narration |
| 00:01 | Welcome to the tutorial on for and each Loops in Ruby. |
| 00:05 | In this tutorial, we will learn: |
| 00:07 | * Meaning of the term “loop” |
| 00:08 | * The different kinds of loops in Ruby |
| 00:11 | * Usage of “for” loop and |
| 00:12 | * Usage of “each” looping construct. |
| 00:14 | Here, we are using: |
| 00:16 | * Ubuntu version 12.04 |
| 00:19 | Ruby 1.9.3 |
| 00:22 | To follow this tutorial, you must have Internet connection. |
| 00:25 | You must also have knowledge of Linux commands, Terminal and Text-editor. |
| 00:30 | If not, for relevant tutorials, please visit our website. |
| 00:34 | Now, let me explain what is referred to as a “loop” in Ruby. |
| 00:38 | A loop is a command or set of commands that are executed a fixed number of times. |
| 00:44 | Ruby has the following main looping statements. |
| 00:47 | * for |
| 00:48 | * each |
| 00:49 | * while |
| 00:49 | * until. |
| 00:50 | In this tutorial, we will learn how to use the for and each looping constructs. |
| 00:55 | Before we begin, please create the following folders in your home directory- |
| 01:02 | ttt, ruby hyphen tutorial, looping hyphen statements. |
| 01:07 | Please create the sub-folders as mentioned there. |
| 01:11 | Now we have created the requisite folders. |
| 01:13 | Let's move ahead. |
| 01:15 | The syntax of the “for” loop in Ruby is as follows: |
| 01:19 | for “variable” in “a collection of objects” |
| 01:22 | ruby code |
| 01:23 | end |
| 01:25 | Let us try to understand it with an example. |
| 01:28 | Create a new file in gedit as shown in the basic level Ruby tutorials |
| 01:32 | and name it for hyphen loop dot rb . |
| 01:36 | I already have a working example of the “for” loop. |
| 01:39 | You can type the code as we go through this example. |
| 01:44 | I have declared a “for” loop in this example. |
| 01:47 | We have a set of numbers 1 to 20. |
| 01:50 | We declare a variable called “i” within the “for” loop. |
| 01:55 | The variable “i” gets initialized to the first element in the set of numbers 1 to 20. |
| 02:00 | The “for” loop declaration causes the code to iterate over each element in the set 1 to 20. |
| 02:07 | The “puts” method declared within the “for” loop is responsible for generating the output. |
| 02:14 | Now, open the terminal and type: |
| 02:17 | ruby space for hyphen loop dot rb and see the output. |
| 02:22 | The output will be an array of numbers 1 to 20. |
| 02:26 | In this example, we declared a “for” loop for an inclusive range. |
| 02:31 | It included all numbers from 1 to 20. |
| 02:35 | Next, we shall look at implementing the “for” loop for a non-inclusive range. |
| 02:41 | Continue to type the next part of the code. |
| 02:44 | Non-inclusive means it will not include the last element in the collection of objects. |
| 02:49 | Here, “for” loop is implemented for a non-inclusive range of numbers 1 to 20. |
| 02:55 | You will notice shortly that the number 20 will not be printed in the output. |
| 02:59 | The last number does not get included when you have 3 dots between numbers. |
| 03:04 | Now, open the terminal and type: ruby space for hyphen loop dot rb |
| 03:13 | and see the output. |
| 03:17 | The output will still be an array of numbers but will not include the number 20. |
| 03:22 | Now, you should be capable enough to write your own “for” loop. |
| 03:27 | The syntax of the “each” loop in Ruby is as follows: |
| 03:31 | “a collection of objects” dot each
do item |
| 03:36 | ruby code
end |
| 03:38 | Let us try to understand it with an example. |
| 03:42 | Create a new file in gedit as shown in the basic level Ruby tutorials |
| 03:46 | and name it each hyphen loop dot rb. |
| 03:50 | I already have a working example of the each loop. |
| 03:53 | You can type the code as we go through this example. |
| 03:58 | I have declared an each loop in this example. |
| 04:03 | We have a set of numbers 1 to 20. |
| 04:06 | We declare a variable called “i” within the each loop. |
| 04:11 | The “i” variable gets initialized to the first element in the set of numbers 1 to 20. |
| 04:17 | The each loop declaration causes the code to iterate over each element in the set 1 to 20. |
| 04:23 | The puts method declared, within the each loop, is responsible for generating the output. |
| 04:30 | Now, open the terminal and type: ruby space each hyphen loop dot rb |
| 04:39 | and see the output. |
| 04:43 | The output will be an array of numbers 1 to 20. |
| 04:46 | In the above example, we declared an each loop for an inclusive range. |
| 04:51 | It included all numbers from 1 to 20. |
| 04:54 | Next we shall look at implementing the each loop for a non-inclusive range. |
| 05:00 | Continue to type this part of the code. |
| 05:04 | Non-inclusive means it will not include the last element in the collection of objects. |
| 05:10 | Here, an each loop is implemented for a non-inclusive range of numbers 1 to 20. |
| 05:16 | You will notice shortly that the number 20 will not be printed in the output. |
| 05:20 | The last number does not get included when you have 3 dots between numbers. |
| 05:25 | Now, open the terminal and type: ruby space each hyphen loop dot rb |
| 05:34 | and see the output. |
| 05:39 | Now you should be capable enough to write your own each loop. |
| 05:44 | How would we determine which looping construct to choose? |
| 05:48 | Let us try to recall the "for" loop construct. |
| 05:53 | In the first example, we iterated over a set of numbers from 1 to 20 using for loop. |
| 05:59 | Execute: ruby space for hyphen loop dot rb in your terminal see the output. |
| 06:08 | Now, look at the code in gedit. |
| 06:11 | When you invoke the for loop, Ruby is actually calling the each method behind the scenes. |
| 06:16 | And, calling each or for will generate the same output. |
| 06:21 | Since the call to for in turn calls each, it is preferable to use the each loop instead. |
| 06:28 | This brings us to the end of this Spoken Tutorial. |
| 06:30 | Let's summarize. |
| 06:32 | In this tutorial, we have learnt: |
| 06:33 | * Usage of for loop |
| 06:35 | * Usage of each construct |
| 06:38 | * Reasoning behind using each instead of for |
| 06:41 | * Examples of using the above looping constructs. |
| 06:45 | As an assignment- |
| 06:47 | Write a ruby program using the appropriate loop construct |
| 06:50 | to create an output of even numbers from a set of numbers, say 1 to 20. |
| 06:56 | Watch the video available at the following link. |
| 07:00 | It summarizes the Spoken Tutorial project. |
| 07:03 | If you do not have good bandwidth, you can download and watch it. |
| 07:08 | The Spoken Tutorial project team: |
| 07:11 | * Conducts workshops using spoken tutorials. |
| 07:14 | * Gives certificates to those who pass an online test. |
| 07:18 | For more details, please write to:
contact@spoken-tutorial.org |
| 07:23 | Spoken Tutorial project is a part of the Talk to a Teacher project. |
| 07:26 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 07:33 | More information on this mission is available at:
spoken hyphen tutorial dot org slash NMEICT hyphen Intro. |
| 07:41 | This is Anjana Nair, signing off. Thank you. |
