WEBVTT 00:00.170 --> 00:03.800 So in previous examples, everything was public. 00:03.830 --> 00:10.310 Now in this video we're going to learn about encapsulation in object oriented design. 00:10.310 --> 00:17.060 So let's create a class that would be called Bankaccount because that's a good example. 00:17.180 --> 00:21.980 And first start with a private field that would be float. 00:22.400 --> 00:26.720 And it would be balance initialized with zero. 00:28.040 --> 00:31.880 So we haven't used the private visibility modifier yet. 00:31.880 --> 00:33.500 So I need to explain that. 00:33.830 --> 00:42.530 So this means that I can only access this field from within this bank account class, its methods, 00:42.530 --> 00:45.710 and I can't access it from outside. 00:46.400 --> 00:52.850 So if I'm going to create this object now also keep in mind that you don't need a constructor. 00:53.240 --> 00:54.710 It's optional. 00:54.770 --> 01:00.800 And I'd like to echo the account balance. 01:00.800 --> 01:04.790 This would This would throw an error because it is private. 01:04.940 --> 01:06.620 So let me run this. 01:09.200 --> 01:10.730 And we've got a fatal error. 01:10.760 --> 01:14.180 Cannot access a private property. 01:15.200 --> 01:17.270 So without encapsulation. 01:17.270 --> 01:23.990 And if the balance would be public, I could do all kind of weird stuff. 01:23.990 --> 01:25.730 So this is a bank account. 01:25.730 --> 01:32.090 And yet I would be able to set the balance at will at -400 maybe. 01:32.120 --> 01:36.050 So this is not how bank account class should work. 01:36.080 --> 01:40.700 It should give us functionality that is safe to use. 01:40.700 --> 01:48.110 So we should either get the balance, we should deposit money and withdraw the money. 01:48.110 --> 01:53.630 But when withdrawing you should not be able to go below the balance. 01:53.660 --> 02:02.390 So that's why to do anything with a bank account, we're gonna use encapsulation by providing public 02:02.390 --> 02:03.500 methods. 02:05.720 --> 02:10.460 Okay, so let's create a get balance function. 02:10.460 --> 02:13.160 This would be a so-called getter. 02:15.710 --> 02:18.890 And it simply returns the balance. 02:18.890 --> 02:21.470 So I do this balance. 02:21.470 --> 02:26.840 That's the way I can access the current balance and echo it. 02:26.840 --> 02:37.700 So maybe I'm just going to do var dump account get balance and I should get zero in this case. 02:39.470 --> 02:40.310 There it is. 02:40.310 --> 02:45.530 So now let's add some methods that will let us modify the balance. 02:46.070 --> 02:55.880 Let's start with deposit where there is one argument called amount and it is void. 02:55.880 --> 03:00.590 So it doesn't return any value. 03:00.590 --> 03:09.790 Now here we can check if the amount is more than zero because we don't want to deposit negative values. 03:10.540 --> 03:15.490 And if that's the case we can add this to the balance. 03:15.490 --> 03:21.160 So this plus equals operator will just add the amount to balance. 03:21.370 --> 03:29.830 So again if we wouldn't check if the amount is non-negative we could accidentally subtract money from 03:29.830 --> 03:33.070 the balance when we try to deposit money. 03:33.700 --> 03:33.970 Okay. 03:34.000 --> 03:36.160 So now this is safe to use. 03:36.160 --> 03:44.110 But something a little bit more complex is to withdraw the money from the account. 03:44.140 --> 03:49.930 So this also accepts an amount and it can return a boolean. 03:49.930 --> 03:55.030 So this would just mean whether it was successful or not. 03:56.350 --> 03:56.650 Okay. 03:56.650 --> 04:02.890 So first we need to make sure that the amount is More than zero. 04:04.300 --> 04:12.370 Another thing is that we need to make sure that the actual balance is more or equal the amount to be 04:12.370 --> 04:13.450 withdrawn. 04:14.710 --> 04:16.780 If that's the case. 04:19.090 --> 04:25.660 We just subtract the amount from the balance and we return true. 04:26.470 --> 04:32.650 Otherwise we just return false which means the operation was not successful. 04:34.870 --> 04:35.110 Okay. 04:35.110 --> 04:38.890 So now let's do a couple of operations in here. 04:38.890 --> 04:41.680 First on the account. 04:43.450 --> 04:45.340 I'm going to deposit something. 04:45.880 --> 04:51.190 Then on the account or from the account I'm going to withdraw 500. 04:51.190 --> 04:56.200 And finally we're going to see what's the remaining deposit. 04:56.710 --> 04:58.750 I expect 500. 04:58.750 --> 05:01.930 And that's the case.