Ruby/C3/for-and-each-Looping-Statements/English-timed
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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.
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00.25 | You must also have knowledge of Linux commands, Terminal and Text-editor.
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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:
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01.19 | for “variable” in “a collection of objects”
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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”
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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.
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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.
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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 digit 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.
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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.
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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.
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04.11 | The “i” variable gets initialized to the first element in the set of numbers 1 to 20.
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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 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.
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04.43 | The output will be an array of numbers 1 to 20.
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04.46 | In the above example we declared an each loop for an inclusive range.
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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.
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05.16 | You will notice shortly that the number 20 will not be printed in the output. |
05.20 | The last digit 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.
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05.53 | In the first example, we iterated over a set of numbers from 1 to 20 using for. |
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.
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06.30 | Let's summarize.
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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
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06.56 | Watch the video available at the following link. |
07.00 | It summarises 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 |