1 00:00:00,630 --> 00:00:02,900 Hello and welcome to this lecture. 2 00:00:02,970 --> 00:00:11,980 In this lecture I'll be explaining what conditional statements are in the Ruby programming language. 3 00:00:12,000 --> 00:00:15,660 What are conditional statements. 4 00:00:15,870 --> 00:00:26,880 Conditional state measures are basically used to perform different actions based on different conditions. 5 00:00:27,900 --> 00:00:34,770 In Ruby and most programming languages they use conditional statements. 6 00:00:34,770 --> 00:00:44,250 So when you write code you may want to perform different actions for different types of decisions. 7 00:00:44,330 --> 00:00:48,420 You do this using conditional statements. 8 00:00:48,420 --> 00:00:53,610 There are three main types of conditional statements in Ruby. 9 00:00:53,610 --> 00:00:57,420 The first is known as the if statement. 10 00:00:57,420 --> 00:01:05,950 Basically what this appears is that the piece of code inside this state may execute if the condition 11 00:01:05,950 --> 00:01:10,300 specified inside the IF statement turns out to be true. 12 00:01:10,950 --> 00:01:18,930 If the condition is false then the second type of conditional statement is executed which is the else 13 00:01:18,990 --> 00:01:19,880 statement. 14 00:01:20,160 --> 00:01:30,390 So who else will execute the code block if the condition in the block is wrong or it evaluates to be 15 00:01:31,150 --> 00:01:32,330 false. 16 00:01:32,460 --> 00:01:38,790 If it's true then there is no action for the house because the code will have executed are there is 17 00:01:38,880 --> 00:01:41,800 another conditional statement that is else. 18 00:01:41,970 --> 00:01:44,090 If so what this does. 19 00:01:44,100 --> 00:01:48,850 It basically specifies a new set of condition. 20 00:01:48,940 --> 00:01:56,850 If the condition in the first block is false so it was both fresh new condition to test the condition 21 00:01:56,910 --> 00:01:59,940 in the first block is faulkes. 22 00:01:59,940 --> 00:02:04,930 Let's quickly illustrate how this works in the first example here. 23 00:02:05,040 --> 00:02:16,950 Quite a variable x which we said is less than 17 so we think if it is less than 17 then display below 24 00:02:16,950 --> 00:02:17,670 17. 25 00:02:17,690 --> 00:02:26,850 If he is not listed in the second block of call what is it tell us if he if x is greater than 27 which 26 00:02:26,850 --> 00:02:35,200 is in new condition then display over 27 else display 17 to 20. 27 00:02:35,670 --> 00:02:43,050 So every time you write a conditional statement you must type an end so that Ruby knows you've ended 28 00:02:43,050 --> 00:02:43,950 the statement. 29 00:02:43,950 --> 00:02:48,870 Ruby is quite unique compared to more so that programming language should only curly braces and all 30 00:02:48,870 --> 00:02:56,430 that Ruby knows what to do once he gets to where each of the conditional statements are equal to what 31 00:02:56,430 --> 00:02:57,180 he has to do. 32 00:02:57,180 --> 00:03:02,610 As long as you put the end when this statement meant Ruby would do the rest. 33 00:03:02,610 --> 00:03:11,260 Another quick example is this we say we test in a quick application here to check the drinking age limit 34 00:03:11,970 --> 00:03:14,030 so we've got conditional statement. 35 00:03:14,040 --> 00:03:22,110 To do that so this is just a simple fit meant to see if this city is equal to London. 36 00:03:22,110 --> 00:03:26,020 Then set the drinking age to 18. 37 00:03:26,280 --> 00:03:31,610 Are the wise set the drinking age to 21. 38 00:03:32,580 --> 00:03:39,760 I've got interactive Ruby so I am going to illustrate how conditional stick meant work. 39 00:03:39,780 --> 00:03:46,470 I've already pre written my move so I'm just going to pace in airline at a time to save me typing. 40 00:03:46,740 --> 00:03:52,920 So first I got a variable and I've set the variable name to blue line. 41 00:03:53,130 --> 00:03:54,440 I press enter. 42 00:03:55,750 --> 00:04:01,980 So begin the conditional testing and the first is if it meant So I'm testing the condition. 43 00:04:01,990 --> 00:04:07,770 Usually when you test conditions you use in comparison operators here. 44 00:04:07,860 --> 00:04:15,760 So I'm seeing even the name that name you they mean if it is equal to blue line then I wanted to do 45 00:04:15,760 --> 00:04:23,940 whatever I specify inside this conditional state so the condition turns out to be true. 46 00:04:24,090 --> 00:04:28,210 It all executed this piece of code. 47 00:04:29,270 --> 00:04:41,350 If it is false I need to add a health condition it will execute the code I put within the health statement. 48 00:04:41,650 --> 00:04:49,410 So if the condition is wrong it will display this message on the screen. 49 00:04:49,840 --> 00:04:55,210 Nothing will happen yet because I have not ended the statement so Ruby doesn't know if I want to write 50 00:04:55,230 --> 00:04:55,810 in. 51 00:04:55,950 --> 00:04:58,080 So now I can end this statement. 52 00:04:58,120 --> 00:04:59,600 Now this statement has ended. 53 00:04:59,600 --> 00:05:04,050 If I press enter to see you are not blue line. 54 00:05:04,260 --> 00:05:12,850 What that means is that it is executing the code in the else statement because the condition in the 55 00:05:13,100 --> 00:05:16,150 statement was not true. 56 00:05:16,780 --> 00:05:21,000 All right I'm going to do another conditional this time going to include the else. 57 00:05:21,040 --> 00:05:23,740 If so and not a condition here empty. 58 00:05:23,730 --> 00:05:25,600 If the name is blueline. 59 00:05:28,040 --> 00:05:32,510 Then I want this message to be displayed. 60 00:05:32,630 --> 00:05:38,000 Blue line gives a good discount if this condition is true if it is not. 61 00:05:38,210 --> 00:05:45,490 I need to specify and else so I'm specifying an else if Okay. 62 00:05:45,500 --> 00:05:55,610 So this darton a new condition yes this testing in new condition here case so if this name if this condition 63 00:05:55,610 --> 00:06:02,690 is not met and put a new quantity on here then name me the name is sequel's to London uni then I need 64 00:06:02,690 --> 00:06:06,390 to specify the piece of code that will execute. 65 00:06:06,770 --> 00:06:15,200 So if the condition in the ELSE is true it will display come on London if it is not true. 66 00:06:15,230 --> 00:06:23,870 I need to specify and else and then specify the code that will display in the else statement. 67 00:06:24,140 --> 00:06:29,150 So the condition is not true in the Healthy of record I want to display. 68 00:06:29,150 --> 00:06:35,020 Is this inside a statement of C not London you or Kim. 69 00:06:35,030 --> 00:06:45,250 Now I mean to end the statement by typing in an end stedman's So that's it for press Enter now the conditional 70 00:06:45,260 --> 00:06:47,010 STD May will execute. 71 00:06:47,360 --> 00:06:56,030 So you can see now says blue line gives a good discount cause the condition in the if statement is true 72 00:06:56,490 --> 00:06:57,970 evaluated to true. 73 00:06:57,990 --> 00:07:01,780 So the piece of code in the else. 74 00:07:01,820 --> 00:07:08,400 If anybody else when not executed only become only the code inside here block. 75 00:07:08,540 --> 00:07:12,890 So that's basically how conditional statements work. 76 00:07:12,890 --> 00:07:15,090 Thanks for watching and buyoff for there.