WEBVTT 00:00.980 --> 00:05.240 Okay, so in this video we're going to learn about the traits. 00:05.420 --> 00:10.580 So traits is just a simple way to add methods to classes. 00:10.670 --> 00:18.470 Without those methods without those classes having to inherit from other classes. 00:19.580 --> 00:20.780 So let's have an example. 00:20.780 --> 00:23.150 Let's create a user class. 00:26.150 --> 00:27.860 So this is something simple. 00:27.860 --> 00:39.050 Let's call it a model a database model that contains some information and is trying to model a database 00:39.050 --> 00:39.950 table. 00:40.580 --> 00:41.660 It is super simple. 00:41.660 --> 00:43.520 It just contains a name. 00:43.520 --> 00:47.480 So we use constructor property promotion in here. 00:48.320 --> 00:53.090 And it will have just one method called save. 00:53.090 --> 00:55.730 So it saves itself. 00:56.570 --> 00:59.450 It's void doesn't return any value. 00:59.450 --> 01:02.900 And we're not going to implement anything here yet. 01:02.900 --> 01:07.820 I'd like to log the information that something has happened. 01:07.940 --> 01:15.540 Specifically I'd like to log that this name was saved. 01:18.450 --> 01:25.980 Okay, so, um, as you can see, this class user does not have this log method. 01:26.010 --> 01:27.510 Now what's logging? 01:27.540 --> 01:35.280 Well, it's just a way of saying what happened in your app so that you can later review those logs to 01:35.310 --> 01:39.120 figure out what has happened in case anything went wrong. 01:40.020 --> 01:46.080 So to actually use a logger inside the user class, we've got a couple of options. 01:46.650 --> 01:50.940 We can use composition something we've seen previously. 01:51.120 --> 01:59.430 We can pass some kind of a logger class that might actually implement a logger interface, so that we 01:59.430 --> 02:02.310 can easily switch between loggers. 02:02.850 --> 02:03.990 So this would work. 02:03.990 --> 02:10.920 We could pass an object through a constructor and then do something like this logger log. 02:11.550 --> 02:13.350 This would be perfectly fine. 02:13.770 --> 02:18.120 Now another way would be to just use a trait. 02:18.160 --> 02:28.360 Now this user class can still implement an interface, but if it would implement an interface that could 02:28.360 --> 02:34.420 be called logger and it can have a function. 02:36.820 --> 02:38.050 Called log. 02:40.060 --> 02:51.280 That accepts a string message and does not return anything if user would implement this interface. 02:51.310 --> 02:56.830 Well, we would have to actually implement this method every single time. 02:56.830 --> 03:00.730 And this is especially not convenient. 03:00.730 --> 03:09.160 If you would be logging something from multiple different classes, then you'd have to implement the 03:09.160 --> 03:13.690 same log method every single time. 03:14.470 --> 03:18.520 So to the rescue we can use a trait. 03:18.550 --> 03:24.160 Now, as said previously, let's create this trait called Loggable. 03:24.190 --> 03:32.410 Trait is just a set of methods that you can easily add to a class in other programming languages. 03:32.440 --> 03:37.480 That's sometimes called a mixin, or also can be called a partial. 03:39.250 --> 03:40.570 So here I can do. 03:40.600 --> 03:46.660 Public function log string message void. 03:48.100 --> 03:58.810 And in PHP we can just do echo saying logging and just output the message and a new line character like 03:58.810 --> 03:59.470 that. 03:59.500 --> 04:05.290 And now let's run this so we can see the error. 04:05.320 --> 04:07.390 Let's run trade speech P. 04:07.840 --> 04:16.120 So the class user contains an abstract method and must therefore be declared abstract or implement the 04:16.120 --> 04:16.570 method. 04:16.570 --> 04:21.550 We are talking about the log method from this interface. 04:22.180 --> 04:30.130 So now having this trait I can reuse it in every single class by just adding this use. 04:31.960 --> 04:32.620 How is it called? 04:32.620 --> 04:34.090 It's called Loggable. 04:35.200 --> 04:36.010 And voila! 04:36.050 --> 04:44.240 Now our user class will have this method defined so we can create an instance of it. 04:44.240 --> 04:48.500 Right now let's create a user that's new user. 04:51.110 --> 04:51.530 Built. 04:51.530 --> 04:56.060 And let's do user save. 04:58.220 --> 04:59.330 And there it is. 04:59.810 --> 05:01.850 We've got the correct message. 05:01.850 --> 05:09.020 Now just to be clear, traits don't necessarily have to be used with an interface. 05:09.830 --> 05:18.140 I think it's just cleaner if you do it this way, because then it's clear that this class requires to 05:18.140 --> 05:25.430 have some kind of methods and trait is there to provide them, but it is perfectly fine to just use 05:25.430 --> 05:31.850 traits like that, and everything still works, and there is actually nothing wrong about that. 05:31.850 --> 05:39.200 So if we are talking about PHP frameworks, I think that Laravel is using traits a lot. 05:39.200 --> 05:45.770 So if you are interested specifically in Laravel, it's pretty useful to understand traits.