WEBVTT 00:00.080 --> 00:04.700 In this lesson, you will learn how to create and build your own custom services. 00:04.700 --> 00:10.430 If you already know how to create custom messages, well, it's going to be very easy to do the same 00:10.430 --> 00:11.660 for a service. 00:11.660 --> 00:14.420 And where will we build our service definition? 00:14.420 --> 00:17.930 Well, we are going to do that inside our. 00:17.930 --> 00:19.010 I'm going to close that. 00:19.310 --> 00:23.450 We're going to do that inside our my robot interfaces okay. 00:23.480 --> 00:25.970 And this package is already fully configured. 00:25.970 --> 00:30.980 So if you were creating the service for the first time with no other interfaces, you would need to 00:31.010 --> 00:32.960 configure the package with. 00:32.990 --> 00:40.100 You see the three lines here in the package dot XML and then those few additional lines also in Cmakelists.txt. 00:40.130 --> 00:43.490 But now let's reuse what we had before. 00:43.490 --> 00:49.550 So let's go to our package My Robot interfaces. 00:49.550 --> 00:52.850 And here I have an MSG folder for messages. 00:52.850 --> 00:58.370 But because I'm going to create services I'm going to create a SRV folder. 00:58.370 --> 01:03.830 And in this SVG folder I will put all the services I have for this application. 01:03.860 --> 01:09.650 Now let's say that I want to create a service to compute a rectangle area, for example. 01:09.650 --> 01:16.580 So I could create also an interface named compute rectangle. 01:18.920 --> 01:21.800 Area dot serve. 01:24.080 --> 01:28.820 And so here are a few tips for the name of the service definitions you're going to use. 01:28.820 --> 01:33.470 So first of all, as we did for messages you will start with an uppercase. 01:33.470 --> 01:38.780 And then each word is going to be separated by an uppercase here okay. 01:38.810 --> 01:44.420 No underscore no dashes no spaces just an uppercase between each word. 01:44.720 --> 01:50.810 Then you also don't say it's a compute rectangle area service or something like that. 01:50.840 --> 01:56.120 You just say compute rectangle area and then dot serve. 01:56.360 --> 02:02.150 And also you see, we use a verb here because as I told you, services are going to be used to do some 02:02.180 --> 02:02.840 actions. 02:02.840 --> 02:09.350 So either we do an action like set something, enable motor or we do a computation. 02:09.350 --> 02:12.200 In this case you see we have compute. 02:12.290 --> 02:12.740 Great. 02:12.740 --> 02:14.120 So let's create that file here. 02:14.120 --> 02:16.580 And now let's edit it in VS code. 02:16.610 --> 02:19.730 Now we have an MSG and an SV folders. 02:19.730 --> 02:20.600 And here. 02:20.600 --> 02:23.090 So what do we expect as the requests. 02:23.720 --> 02:25.490 And let's use float numbers. 02:25.490 --> 02:31.100 So float 64 we expect the length of the rectangle. 02:31.100 --> 02:34.610 And then another float with the width. 02:34.610 --> 02:38.270 And with this we can compute the rectangle area. 02:38.270 --> 02:40.820 And now you see I add three dashes. 02:40.820 --> 02:47.420 Actually the three dashes is the first thing you add okay this is a valid service definition. 02:47.420 --> 02:48.560 It's simply empty. 02:48.560 --> 02:51.200 So we have no request and no response. 02:51.200 --> 02:56.550 But this is valid and you need to put three dashes anyway for any service definition. 02:57.000 --> 03:00.330 And this, for example, is also a valid service definition. 03:00.330 --> 03:03.360 You could have a request, but no response. 03:03.390 --> 03:06.120 Of course, here we are expecting to return something. 03:06.120 --> 03:08.250 So let's add a response. 03:08.250 --> 03:11.040 And the response is also going to be a float number. 03:11.070 --> 03:16.440 Let's name it area because we want to compute the rectangle area. 03:16.470 --> 03:16.950 Great. 03:16.980 --> 03:18.660 Now let's save that. 03:18.660 --> 03:25.770 And the only thing we need to do for that service is to add it to the cmakelists.txt we have here already. 03:25.770 --> 03:29.040 One line for the message I'm going to go back to a new line. 03:29.040 --> 03:32.760 And very important, don't add any comma or anything here. 03:32.760 --> 03:35.670 It's just one definition per line. 03:36.060 --> 03:38.280 And this time we need to go to the SRV. 03:38.280 --> 03:44.040 So SRV slash compute rectangle. 03:46.260 --> 03:48.180 Area dot service. 03:48.210 --> 03:52.110 So that's the path for the file I will save that. 03:52.560 --> 03:55.890 And then we can build it so we can build the package. 03:56.820 --> 04:02.100 Let's do a call on build with packages. 04:02.100 --> 04:05.610 Select my robot interfaces. 04:06.390 --> 04:06.810 Okay. 04:06.840 --> 04:10.470 And you might have some logs like that sometimes. 04:10.470 --> 04:13.770 Well you can ignore it okay. 04:13.770 --> 04:20.400 Because this time well it says that you have built some messages in one or more underlying workspaces. 04:20.400 --> 04:22.350 But what he is not really the case. 04:22.350 --> 04:25.980 So I guess that sometimes they detect some false positives for this warning. 04:25.980 --> 04:26.880 And you have this warning. 04:26.880 --> 04:27.600 But here. 04:27.630 --> 04:32.610 Well if you make sure you always build in the same place, you will not have any problem. 04:32.610 --> 04:34.020 So this is just a warning. 04:34.020 --> 04:34.890 It's nothing. 04:34.890 --> 04:37.380 You see it's still working great. 04:37.380 --> 04:46.680 And now for example, in this terminal let's source the environment and we can do Ros2 interface show 04:46.710 --> 04:50.700 with my robot interfaces. 04:50.700 --> 04:51.960 You see now I have the choice. 04:51.960 --> 04:53.730 If I press tab twice. 04:54.090 --> 04:57.330 I see that I have those two interfaces. 04:57.780 --> 05:00.900 So let's see this one. 05:00.900 --> 05:02.730 And that's the one I have created. 05:02.760 --> 05:06.030 And if you see this, it means that your interface is correctly built. 05:06.030 --> 05:08.640 And you can use your service in your code. 05:08.640 --> 05:10.320 So I'm not going to do the code here. 05:10.320 --> 05:12.480 But it's very simple okay. 05:12.480 --> 05:16.950 In Python you will just just like we did here. 05:16.950 --> 05:23.940 You will do from my robot interfaces dot solve import compute rectangle area. 05:23.940 --> 05:34.470 And then for Cplusplus you will do include my robot interfaces slash service slash compute rectangle 05:34.470 --> 05:36.210 area dot HTTP. 05:36.330 --> 05:38.100 And you will have two underscores. 05:38.100 --> 05:40.920 So you will have one underscore between each word. 05:41.550 --> 05:43.980 Because we have added a uppercase here. 05:43.980 --> 05:44.790 And that's it. 05:44.790 --> 05:50.130 So you can see that creating new interfaces from now on is quite easy and quick.