Conditional Statements

Quick reference

• 00:04 In this video I want to talk about comparison statements or
• 00:06 as they're actually called conditional statements.
• 00:09 I like to refer to them as comparison statements because we're going to use our
• 00:12 comparison operators.
• 00:14 But they're technically called conditional statements.
• 00:16 And they allow us to run conditions, to do tests and make decisions in our code.
• 00:22 So they look just like this, this is the format.
• 00:24 If some condition, do something, and then end.
• 00:27 So commonly these are called if statements.
• 00:30 We're going to look at if statements, if/else statements, and
• 00:32 if/else/if statements in this video.
• 00:34 To do this, we go if, let's say,
• 00:39 name = John, puts Hello John, end.
• 00:45 So if we come up here and let's go, puts Enter,
• 00:51 no let's do print, print Enter your name.
• 00:56 And then name = gets.
• 00:58 We need to put a .chomp at the end of this gets.
• 01:01 I didn't mention the chomp in the last video when we talked about gets,
• 01:04 but chomp removes the line break that gets put on the end of each gets.
• 01:09 So when I type in John, it actually looks like this, John with a line break.
• 01:15 Remember when puts puts a line break behind everything,
• 01:18 print does not, that's why it's all on one line here.
• 01:21 Same thing with gets.
• 01:22 So we just put a chomp on there.
• 01:23 Now if we save this and run it again, enter your name, John, says, Hello John.
• 01:28 If we run it again, enter your name, Bill, nothing happens.
• 01:31 So look at the flow of this program.
• 01:33 If this condition is true, do this code, otherwise don't do anything.
• 01:39 That's an if statement.
• 01:40 We can do other things as well.
• 01:42 We can do else statements.
• 01:44 So if this is true, do this, else do something else.
• 01:47 And an else statement is very easy.
• 01:49 We just type in else and
• 01:52 then whatever block of code we want we put in right here.
• 01:55 So let's put puts, I don't know you, right?
• 02:02 So if we save this and run it, if you enter your name,
• 02:05 John, it says Hello John, and it ends.
• 02:07 Once this happens, the whole program ends if this is true.
• 02:11 If not, it drops down to the else statement and it runs the else statement.
• 02:16 So let's run this program again, Enter your name, Bill.
• 02:20 I don't know you, right?
• 02:21 So that's if, that's else, we can also do else if,
• 02:25 which usually goes up here, so it's just E-L-S-I-F, elsif.
• 02:29 Now we can run another condition,
• 02:33 we can say if name = Bill puts Hiya Bill.
• 02:39 So looking at the flow of our program now,
• 02:42 it's going to start out if the name is John, it'll do this and then end.
• 02:45 Otherwise, it'll drop down and do this.
• 02:48 Is the name Bill?
• 02:49 If so, it'll do this, and then end.
• 02:52 If none of these are true,
• 02:54 then it'll execute this else here at the bottom that says, I don't know you.
• 02:57 So if we save it and run it, if we go, John, Hello John, and then it ends.
• 03:02 If we go Bill, Hiya Bill, and then it ends.
• 03:06 If we see Tim, I don't know you.
• 03:08 So those are conditional statements.
• 03:10 They're very, very useful.
• 03:12 You are going to use these all the time.
• 03:13 I mean almost probably the most important thing in all programming languages.
• 03:17 These if statements, if/else statements, they're just used constantly.
• 03:21 All programs, always, forever, you're going to use these.
• 03:24 So kind of get used to this format.
• 03:26 It's just if, else, and then it always ends here at the bottom.
• 03:30 Anything inside here, this block of code.
• 03:33 And we can do lots of lines of code here,
• 03:36 we can put whole programs in here, doesn't really matter.
• 03:39 It only happens if this line is true.
• 03:42 If it's not true, and we can do anything.
• 03:44 We don't have to do a string.
• 03:46 We can say if number is greater than 1, do this.
• 03:51 If number is not equal to.
• 03:54 We can use all of our comparison operators in this line,
• 03:57 in this conditional statement right here.
• 03:59 So those are conditional statements, very useful.
• 04:01 In the next video, we're going to look at multiple conditional comparison operators.

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