1 00:00:00,950 --> 00:00:01,910 Hello again, everyone. 2 00:00:02,180 --> 00:00:07,270 So in this lesson, we're going to talk about interface, so let's get to it. 3 00:00:08,780 --> 00:00:18,290 So normally, as you know, interface does not exist in JavaScript, so creating a type safe structure 4 00:00:18,290 --> 00:00:19,770 is inherently difficult. 5 00:00:20,870 --> 00:00:28,460 We can say that the interfaces and typescript are basically developed to eliminate this difficulty and 6 00:00:28,460 --> 00:00:30,500 we really wouldn't be too far wrong. 7 00:00:32,000 --> 00:00:38,850 We could also say that the interface in typescript is basically a type definition. 8 00:00:39,890 --> 00:00:47,030 So while classes and functions describe the behavior of objects we can think of, interfaces is defining 9 00:00:47,420 --> 00:00:48,860 object types. 10 00:00:50,490 --> 00:00:56,160 Now, if you've worked with languages such as Java and C Sharp before, you're already familiar with 11 00:00:56,160 --> 00:00:56,820 this topic. 12 00:00:58,920 --> 00:01:05,910 But here we've already mentioned that we can collect similar features in one class and then can extend 13 00:01:05,910 --> 00:01:08,310 them to other classes when necessary. 14 00:01:09,570 --> 00:01:12,660 Actually, the interface works similarly. 15 00:01:14,570 --> 00:01:21,020 We can say that there are some differences, and if you want to make it clearer with a simple example, 16 00:01:21,920 --> 00:01:28,730 yes, let's we use the interface keyword to make a definition and then write the name. 17 00:01:34,440 --> 00:01:39,300 So also defined variables as strings, username, password and email. 18 00:01:52,420 --> 00:01:57,520 Now, here I'm writing a simple method that is using this interface and writing console. 19 00:02:05,630 --> 00:02:08,420 And the person has been registered. 20 00:02:21,610 --> 00:02:23,740 So when I call this method, look here. 21 00:02:29,360 --> 00:02:31,010 We see the parameters at once. 22 00:02:48,260 --> 00:02:51,560 So I need to send all parameters in this interface. 23 00:02:53,030 --> 00:02:59,480 And so we've added all parameters, and as you can see, when I add all the parameters, the error display 24 00:02:59,480 --> 00:02:59,960 is gone. 25 00:03:02,090 --> 00:03:08,210 So now I'm changing this variable to optional, so that means I'll put a question mark in here. 26 00:03:12,810 --> 00:03:15,840 So when I delete this parameter, there's no problem. 27 00:03:19,870 --> 00:03:22,660 So now, look, when I change this string value to a number. 28 00:03:27,480 --> 00:03:35,250 We got an error again, because the program warns me that there's no variable of type, no year, we 29 00:03:35,250 --> 00:03:39,330 already know that, but I wanted you to see it again. 30 00:03:42,100 --> 00:03:44,770 So now let's define a class. 31 00:03:49,210 --> 00:03:55,690 So I want to make the difference a little more clear and you'll see why, so I'll prepare a class and 32 00:03:55,690 --> 00:04:01,180 define variables and then after making these definitions, I'll create an object. 33 00:04:08,740 --> 00:04:15,670 And look at this, so I'm only using the name variable for this object, and I'm not going to give any 34 00:04:15,670 --> 00:04:17,280 value to the other variables. 35 00:04:18,460 --> 00:04:22,420 So now I'm writing a method for the class, just like in here. 36 00:04:28,540 --> 00:04:31,930 And when I call this method, I don't get any errors. 37 00:04:32,890 --> 00:04:33,580 Why is that? 38 00:04:33,610 --> 00:04:41,470 Well, I've only to find one variable here, but it's OK for class because while interfaces want to 39 00:04:41,470 --> 00:04:47,730 use all the variables define that is just not the case for classes. 40 00:04:49,150 --> 00:04:50,460 So you see where we're going with it. 41 00:04:51,820 --> 00:04:56,370 If we are to define all variables, we got to use interface. 42 00:04:56,800 --> 00:05:03,910 But if you're not in that situation, we can say that we can use and define class. 43 00:05:07,960 --> 00:05:14,980 So you remember earlier when we were extending the class, well, likewise, we can implement interfaces. 44 00:05:18,080 --> 00:05:19,400 Just use the same logic. 45 00:05:24,690 --> 00:05:29,160 All right, my friends, so we're going to talk about generics in our next lesson. 46 00:05:29,760 --> 00:05:30,640 Hope to see you there. 47 00:05:31,410 --> 00:05:31,880 All right.