WEBVTT 00:00.080 --> 00:02.180 This is the solution for the activity. 00:02.210 --> 00:06.680 Number three, we will add a new service server inside the number counter. 00:06.710 --> 00:08.300 Note here that we have created. 00:08.300 --> 00:12.680 In the last section I will only provide a video for the Python solution. 00:12.680 --> 00:18.950 But of course you can find the complete C plus plus solution inside the code archive that you can download 00:18.950 --> 00:25.220 at the end of this section, so you can open the number counter dot p y that we've created before. 00:25.220 --> 00:31.580 And actually before we write anything, let's just go to the terminal and let's check the interface 00:31.580 --> 00:33.620 that we will need to use. 00:33.620 --> 00:37.310 So let's do Ros2 interface show. 00:37.310 --> 00:38.540 And I gave you that one. 00:38.570 --> 00:46.880 I gave you example interfaces slash SRV slash set bool. 00:48.680 --> 00:54.260 So you can see we have some commands first saying that this is like something to test. 00:54.260 --> 01:04.440 And then we have a request here that contains only one field name is data and the type is bool for boolean. 01:04.470 --> 01:07.860 Then we have the three dashes and then we have the response. 01:07.860 --> 01:11.640 So that's what we're going to receive from the server to the client. 01:11.640 --> 01:14.940 So a success flag is going to be true or false. 01:14.940 --> 01:16.590 And then a message. 01:16.590 --> 01:21.450 For example if you have an error you could give more information about what went wrong. 01:21.450 --> 01:22.170 So great. 01:22.170 --> 01:23.700 We know the interface. 01:23.700 --> 01:25.260 So that's the package. 01:25.260 --> 01:27.930 And we know what's inside the interface. 01:27.930 --> 01:29.610 So now we can go back to the code. 01:29.640 --> 01:32.130 And in this number counter dot p y. 01:32.160 --> 01:34.650 Let's add this interface. 01:34.800 --> 01:41.670 So after the other imports here I'm going to do from example interfaces dot. 01:41.670 --> 01:49.110 And here it's sorry because we import a service interface import set bool. 01:49.140 --> 01:49.710 All right. 01:49.710 --> 01:54.660 And well we've already added example interfaces into the package dot XML. 01:54.660 --> 01:56.100 So the dependency for that. 01:56.100 --> 01:57.810 So we don't need to do it anymore. 01:57.840 --> 01:59.880 Then I'm going to add a service server. 01:59.880 --> 02:01.890 Where do I add this service? 02:01.920 --> 02:04.500 Well, just in the constructor after. 02:04.530 --> 02:07.170 Well, for example, we have a publisher a subscriber. 02:07.170 --> 02:11.070 I'm going to add it right here before the end log. 02:11.070 --> 02:13.740 So let's name it self dot. 02:14.250 --> 02:17.130 We want to reset the counter. 02:17.130 --> 02:21.660 So reset counter service for example. 02:21.660 --> 02:26.490 And that's going to be self dot create service. 02:26.760 --> 02:30.150 We need to provide the type set bool. 02:30.240 --> 02:32.430 We need to provide the name. 02:32.430 --> 02:33.750 So what's the name. 02:33.750 --> 02:36.600 Well we decided here because we created the service. 02:36.600 --> 02:40.530 When we create the server and we just want to reset the counter. 02:40.530 --> 02:42.810 So let's call it reset counter. 02:43.170 --> 02:44.910 Let's keep things simple here. 02:44.910 --> 02:47.940 And finally we will need to provide a callback. 02:47.970 --> 02:48.450 Okay. 02:48.480 --> 02:52.380 Because when the node is spinning it can receive requests. 02:52.380 --> 02:58.290 When we receive a request, in order to be able to process it we have to write a callback. 02:58.320 --> 03:01.840 And so let's just add a callback inside the class here. 03:01.870 --> 03:03.490 The order doesn't matter. 03:03.520 --> 03:13.270 Make sure that the function is inside the class and let's name it callback reset counter okay with self. 03:13.270 --> 03:18.220 And then we have the request and the response request response. 03:18.280 --> 03:18.730 Okay. 03:18.730 --> 03:21.820 So as you can see for a subscriber we just get the message. 03:21.820 --> 03:25.090 But for a service server we get the request. 03:25.090 --> 03:27.670 And already the response object. 03:27.670 --> 03:29.860 I'm going to make it explicit here. 03:29.860 --> 03:35.050 So the request is set bull dot request. 03:35.050 --> 03:40.930 And the response is set bull dot response. 03:42.130 --> 03:47.440 All right let's just put pass for now so we can finish this line here. 03:47.440 --> 03:52.630 So I'm going to put self dot callback reset counter. 03:53.200 --> 03:55.990 And let's go to a new line here to make it a bit cleaner. 03:55.990 --> 04:00.320 So you see we create a service with the interface the name and the callback. 04:00.320 --> 04:05.480 Now let's go to the callback and let's implement the callback. 04:05.480 --> 04:06.770 So what do we want to do? 04:06.800 --> 04:10.520 You see we receive here a wool data. 04:10.520 --> 04:14.150 So let's say that we want to reset the counter if this is true okay. 04:14.150 --> 04:18.020 So if you provide false we are not going to reset the counter. 04:18.710 --> 04:23.450 So I can do if request dot data. 04:23.510 --> 04:28.820 If this is true then we do self dot counter. 04:29.390 --> 04:35.360 So the counter is here is equal to zero just as simple as that. 04:35.360 --> 04:38.900 So you see we initialize the counter to zero when we start the node. 04:38.900 --> 04:46.400 Then whenever we receive a message here on the number topic we're going to add the data to the counter. 04:46.400 --> 04:53.360 But if we receive a request for this service server here reset counter, we also reset the counter to 04:53.390 --> 04:53.990 zero. 04:53.990 --> 04:56.090 And then well that's the action okay. 04:56.120 --> 04:59.960 The action is if we request to reset the counter. 04:59.990 --> 05:02.030 Then we reset the counter to zero. 05:02.060 --> 05:06.740 But then we need to also provide a response for the client. 05:06.740 --> 05:09.200 So response dot. 05:09.200 --> 05:13.640 And we have two things we have success and message. 05:14.240 --> 05:15.980 So let's do response dot. 05:15.980 --> 05:20.810 Success is equal to true and response. 05:20.810 --> 05:22.460 Let's add a message. 05:23.180 --> 05:26.780 You could just leave it empty but let's just say okay. 05:26.870 --> 05:30.860 Or let's say counter has been reset. 05:30.890 --> 05:31.610 All right. 05:31.610 --> 05:33.500 And let's add an else. 05:33.680 --> 05:33.980 Okay. 05:34.010 --> 05:39.830 If the data here is false, then we are not going to reset the counter. 05:39.830 --> 05:44.810 And we are going to put the response dot success for example false. 05:44.840 --> 05:56.840 Just for the example and response dot message let's say counter has not been reset. 05:57.620 --> 06:01.620 Well here it's just because you provide it false in the request. 06:01.620 --> 06:06.750 But if, for example, you would have a service to enable a motor or something like that, then you 06:06.750 --> 06:08.490 would probably need to do some checks. 06:08.490 --> 06:15.030 And if some checks are failing, then you could return a response with a message that explained what 06:15.030 --> 06:15.930 was the issue. 06:15.960 --> 06:17.400 Okay, so that's it. 06:17.400 --> 06:22.320 But actually we need to return the response. 06:22.320 --> 06:23.550 So very important. 06:23.580 --> 06:23.760 Okay. 06:23.790 --> 06:24.660 Don't forget that. 06:24.690 --> 06:28.020 Otherwise you will get an error when you run the service. 06:28.050 --> 06:28.590 Okay. 06:28.620 --> 06:31.770 So you see we just do the action. 06:31.770 --> 06:35.730 We fill the response and we return the response. 06:35.730 --> 06:37.170 And basically that's it. 06:37.170 --> 06:39.150 That's it for this activity, for the code. 06:39.150 --> 06:40.470 It's not much to do. 06:40.530 --> 06:40.830 Okay. 06:40.860 --> 06:44.010 So to recap we have added the interface here. 06:44.340 --> 06:48.690 And then we create a service server inside the constructor. 06:48.690 --> 06:52.380 And we have a callback to handle incoming requests. 06:52.410 --> 06:54.750 Now I'm going to save that. 06:54.840 --> 07:00.720 We don't need to do anything else in the setup.py because we already have the number counter executable 07:00.750 --> 07:03.180 here, so nothing to do. 07:03.210 --> 07:09.990 Let's go back to the terminal and well let's build it again because I'm not sure if last time I built 07:10.020 --> 07:19.830 was with Simulink install called build packages select and the Python package. 07:21.780 --> 07:22.260 Okay. 07:22.260 --> 07:29.550 And I'm just going to start new terminals so that everything is sourced correctly. 07:29.550 --> 07:34.860 And to test this well I'm gonna start first the number publisher. 07:34.860 --> 07:45.960 So Ros to run number um that's my Pi PG with number publisher here I'm going to start the number counter 07:45.990 --> 07:47.700 here Ros to run. 07:49.860 --> 07:58.500 With number counter I start with two because well the counter is only going to be increased if we receive 07:58.530 --> 07:59.980 data on the number topic. 07:59.980 --> 08:01.810 So we also need the number publisher. 08:01.810 --> 08:07.630 So let's see what we have here Ros2 service list. 08:08.950 --> 08:13.960 So you see we have lots of services because we have those that are automatically generated. 08:13.960 --> 08:24.400 But then we find the reset counter okay Ros2 service type with reset counter. 08:25.480 --> 08:29.680 And we find set bool interface okay. 08:29.710 --> 08:31.900 So let's make a simple test here. 08:31.930 --> 08:38.050 Let's clear that and we can do Ros2 service call with. 08:38.080 --> 08:41.110 So that's reset counter. 08:41.200 --> 08:44.620 And then example interfaces set bool. 08:44.620 --> 08:50.620 And we had a field named data which is supposed to be a boolean. 08:50.620 --> 08:52.180 So let's put true. 08:53.560 --> 09:03.170 And you see we have here success true Message counter has been reset, but we don't see anything because, 09:03.200 --> 09:14.870 well, to see something we need to do a rostopic echo with the number count and you can see the counter 09:14.900 --> 09:15.890 going up. 09:15.890 --> 09:23.630 And then if I call the service again, you will see that we start at zero again. 09:23.660 --> 09:25.820 You see we went back to zero okay. 09:25.850 --> 09:32.150 Every time I run the service, every time I make a request we start at zero. 09:32.180 --> 09:37.370 Now let's say I make a request, but I put data false. 09:38.330 --> 09:41.180 In this case, the service is still working correctly. 09:41.180 --> 09:43.400 But you see, because we have provided false. 09:43.400 --> 09:48.200 And then in the code we said that if it's false we don't reset the counter. 09:48.230 --> 09:50.420 Then you see here we receive success. 09:50.420 --> 09:56.360 False counter has not been reset and you can see it also here the counter is not reset. 09:56.390 --> 09:56.990 All right. 09:56.990 --> 10:04.340 So with those two cases, you can see the application is working. 10:06.470 --> 10:06.890 All right. 10:06.920 --> 10:10.880 And if you want you can also create some code for the client. 10:10.880 --> 10:15.800 So you could use the for example add to in clients no OOP. 10:15.980 --> 10:21.470 And modify this to create a simple script to call this new service. 10:21.500 --> 10:24.980 Or you could also use that one with object oriented programming. 10:24.980 --> 10:27.050 So you can do that if you want to practice a bit more. 10:27.050 --> 10:29.480 And the activity is now finished. 10:29.480 --> 10:33.140 Once again, you can download all the code at the end of this section. 10:33.170 --> 10:33.530 Okay. 10:33.560 --> 10:37.100 The C plus plus solution is going to be exact same stuff okay. 10:37.100 --> 10:38.810 Just using the C plus plus syntax. 10:38.810 --> 10:40.460 And just a final note here. 10:40.460 --> 10:46.220 If I come back to this number counter, you can see that in a node you can have many different things. 10:46.220 --> 10:52.100 Here we have one publisher one subscriber one service server okay. 10:52.130 --> 10:54.350 So you can have any combination of those. 10:54.350 --> 10:56.750 You can create as many as you want. 10:56.780 --> 10:59.210 Just make sure that they all have a different name.