WEBVTT 00:00.050 --> 00:04.040 In this lesson you will learn how to create a Cplusplus node. 00:04.040 --> 00:08.990 You will write the node, compile it and run it, and we're going to follow the same structure. 00:08.990 --> 00:12.620 As for the Python node, we're going to first write a very minimal code. 00:12.620 --> 00:17.660 And then in the next lesson you will have the object oriented programming way of writing the code, 00:17.690 --> 00:22.670 plus the full template that you can use for any future node that you create. 00:22.670 --> 00:24.260 And let's get started. 00:24.260 --> 00:32.900 So we are going to go first inside our roster workspace and then the source directory and then the my 00:32.930 --> 00:34.670 CPP package. 00:34.670 --> 00:39.410 So inside this package we have a include and a source folder. 00:39.410 --> 00:43.100 We are going to go inside the source folder of that package. 00:43.100 --> 00:44.930 And here we have nothing. 00:44.930 --> 00:46.550 So let's create a file. 00:46.580 --> 00:51.680 Touch my first node dot cpp. 00:51.680 --> 00:54.260 So we use the CPP extension. 00:54.290 --> 00:54.710 All right. 00:54.740 --> 01:01.310 So that's where you will create your cplusplus files inside the source folder of the package. 01:01.310 --> 01:04.050 And now let's edit that with VSCode. 01:04.050 --> 01:11.700 So I'm going to go back again here to the source folder of the workspace called Dot. 01:12.780 --> 01:21.450 And let's find the file which is going to be right here in the my CP package. 01:21.450 --> 01:23.850 And you see I have my first node CP. 01:23.850 --> 01:26.130 So let's start with the includes. 01:26.130 --> 01:28.470 And we only have one include here. 01:28.470 --> 01:38.970 So we're going to do include and then RCL CP slash RCL CP dot HP. 01:38.970 --> 01:43.140 And you can see here again I have the auto completion. 01:43.140 --> 01:47.190 If you don't have the auto completion you need to go back to the extensions here. 01:47.190 --> 01:53.430 Make sure you have installed the Ros extension by Microsoft and then maybe start the VSCode again. 01:53.970 --> 01:59.190 Okay, so include RCL, CP and then RCL, cp, HP. 01:59.340 --> 02:03.170 At this point I would also suggest to already save the file. 02:04.310 --> 02:09.920 Okay, you see, we have an error and then it's recognized again. 02:09.920 --> 02:16.010 So save the file because then if you use the clcp functionalities later, if you haven't saved the file 02:16.010 --> 02:18.890 maybe you will have some issues with the autocompletion. 02:18.890 --> 02:22.250 So save the file after you include something in Cplusplus. 02:22.250 --> 02:23.660 I would recommend to do that. 02:23.660 --> 02:26.810 And then well, what do we need to do in a Cplusplus program? 02:26.810 --> 02:29.990 We need to create a main function. 02:29.990 --> 02:33.320 So let's just create one with arg c. 02:33.350 --> 02:39.080 So number of arguments and then this for the arguments okay. 02:39.080 --> 02:40.640 So there's nothing special here. 02:40.640 --> 02:43.760 It's just a standard main structure for C plus plus. 02:43.760 --> 02:46.280 And what do we do inside the Ros2 program. 02:46.280 --> 02:55.490 Well first we initialize ros2 communication with our clcp then colon colon init okay. 02:55.520 --> 03:01.670 So inside the clcp library we have the init function just like we had in Python. 03:02.120 --> 03:04.850 And here we can pass the arguments of the main. 03:04.850 --> 03:07.400 So argc and argv. 03:08.450 --> 03:14.000 So that's the first thing we will do every time we initialize ros2 communications. 03:14.000 --> 03:16.340 Then we're going to do some stuff. 03:16.340 --> 03:21.680 And the last thing we will do is our clcp shut down. 03:22.040 --> 03:22.520 Okay. 03:22.520 --> 03:24.500 Just like we did in Python. 03:24.500 --> 03:27.860 But of course with the C plus plus syntax and after shutdown. 03:27.860 --> 03:30.110 Well because you see it's a int. 03:30.110 --> 03:32.060 So we need to return an integer. 03:32.210 --> 03:33.980 Let's return zero. 03:34.010 --> 03:34.520 Okay. 03:34.520 --> 03:37.310 So that's the first thing you will do in a C plus plus program. 03:37.310 --> 03:40.310 And that's the last thing you will do in the middle. 03:40.310 --> 03:42.470 We can create nodes and do all sorts of stuff. 03:42.470 --> 03:44.360 But first you initialize Ros2. 03:44.390 --> 03:47.330 And then at the end you shut down Ros2 and you return. 03:47.360 --> 03:49.640 Now let's create a node. 03:49.640 --> 03:51.770 So what type we will give. 03:51.800 --> 03:54.500 Let's just use the auto type. 03:54.830 --> 03:57.380 So auto node is equal to. 03:57.410 --> 04:00.350 And we are not just going to create a node. 04:00.350 --> 04:03.680 We are going to actually create a pointer to a node. 04:03.680 --> 04:08.870 and in Ros2 you will see that we use pointers for everything and actually not just pointers. 04:08.870 --> 04:13.580 We're going to use smart pointers and in this case a shared pointer. 04:13.580 --> 04:18.320 And if you don't know anything about smart pointers, well maybe just find a quick tutorial online to 04:18.350 --> 04:19.580 get a few explanations. 04:19.580 --> 04:20.750 But it's not that hard. 04:20.750 --> 04:25.610 It's just going to take care of allocating memory and destroying the memory for you, so you don't need 04:25.610 --> 04:27.080 to worry about that. 04:27.080 --> 04:29.870 And in Ros two everything is using those pointers. 04:29.870 --> 04:35.660 So at the beginning it might be a bit complicated to understand, but as you get used to it it's always 04:35.660 --> 04:36.440 the same thing. 04:36.440 --> 04:46.700 So let's do STD make shared to create a pointer of an object and what is going to be the object rcl 04:46.730 --> 04:49.310 cpp node. 04:49.340 --> 04:55.400 Okay, so we get the node class from rcl cpp directly okay. 04:55.430 --> 04:59.660 So here with this we open and close the parentheses. 04:59.690 --> 05:03.410 With this we create a node object. 05:03.410 --> 05:07.180 And actually here we create a shared pointer to a node object. 05:07.180 --> 05:15.640 So you can see now the auto is actually a shared pointer of an lclc-rp node. 05:15.670 --> 05:15.970 Okay. 05:16.000 --> 05:19.720 So that's how you create a node in Ros2 with C plus plus. 05:19.720 --> 05:23.080 And then well we can do the same thing as we did with Python. 05:23.080 --> 05:28.090 We can also make the node print something because this is the minimum code. 05:28.090 --> 05:30.100 But well it's not going to do anything. 05:30.100 --> 05:31.540 So let's do node. 05:31.540 --> 05:35.230 And because this is a pointer we need to use an arrow. 05:35.410 --> 05:35.830 Okay. 05:35.860 --> 05:39.970 If you just use a dot you're going to interact with the shared pointer. 05:40.000 --> 05:44.470 If you use an arrow you interact with the object inside the shared pointer. 05:44.470 --> 05:49.720 And we have a get logger functionality and actually to print something. 05:49.720 --> 05:56.380 So to use a log we are going to use the RCL cpp info like that. 05:56.380 --> 06:01.990 And then we're going to put node get logger as the first argument. 06:01.990 --> 06:06.460 And then the second argument is going to be the log itself. 06:06.490 --> 06:07.660 So hello, world. 06:07.750 --> 06:11.680 And you can construct a string here just like that. 06:11.680 --> 06:13.510 Let's not forget the semicolon. 06:13.540 --> 06:14.050 All right. 06:14.050 --> 06:17.380 So lclc-rp underscore info all uppercase. 06:17.380 --> 06:19.030 And then you do node. 06:19.030 --> 06:21.520 So the node you've created getlogger. 06:21.670 --> 06:26.110 And then the log you want to print okay let's save that. 06:26.110 --> 06:27.400 And now how to test it. 06:27.400 --> 06:33.790 So with Python we could already test it by just making the file executable and running the file as Python 06:33.790 --> 06:35.890 was an interpreted language. 06:35.890 --> 06:37.930 But C plus plus you cannot do that. 06:37.930 --> 06:40.840 You need to build the code anyway. 06:40.840 --> 06:42.070 And how to build the code. 06:42.070 --> 06:43.780 How to create an executable. 06:43.780 --> 06:50.050 Well, this time here we will go to the Cmakelists.txt and well I don't want this. 06:50.050 --> 06:53.170 And you see I have already the syntax highlighting. 06:53.170 --> 06:58.780 If you don't have this, make sure you have the CMake extension here by Twx. 06:58.810 --> 06:58.990 Okay. 06:58.990 --> 07:01.270 That's the one that I'm using here for this course. 07:02.530 --> 07:04.900 So let's go back to Cmakelists.txt. 07:05.380 --> 07:09.790 And we're going to write here the rules to create executables for Cplusplus. 07:09.790 --> 07:12.610 But first let's do a bit of cleanup. 07:12.610 --> 07:17.050 So you see we have here the minimum required version for CMake. 07:17.050 --> 07:18.550 Some stuff for the compiler. 07:18.550 --> 07:20.740 We find some dependencies okay. 07:20.740 --> 07:26.050 So we have a CMake that's going to be well because this is a C plus plus package. 07:26.050 --> 07:29.110 And then we have RCL cpp you see. 07:29.140 --> 07:35.260 So if you add a new dependency in a C plus plus package you will have to add the dependency here. 07:35.560 --> 07:35.950 Okay. 07:35.980 --> 07:40.840 But if you need the dependency to compile some stuff, you will also need to find the package here. 07:41.350 --> 07:42.490 And then we have this. 07:42.520 --> 07:48.250 If build testing with some testing stuff that we actually don't need right now. 07:48.250 --> 07:52.390 So usually if I don't need that I'm just removing it okay. 07:52.420 --> 07:53.560 It's a bit cleaner. 07:53.560 --> 07:59.320 And we finish the CMake list.txt with payment package. 07:59.320 --> 08:00.910 So that should be the last line. 08:00.910 --> 08:02.680 So make sure you don't remove that one. 08:02.680 --> 08:04.600 And now how to add an executable. 08:04.600 --> 08:10.600 Well after you find the dependencies parentheses and before the event package line we will add. 08:10.600 --> 08:16.570 So add executable and you need to choose a name for your executable. 08:16.570 --> 08:19.870 So for example cpp node. 08:19.900 --> 08:22.870 Okay this is whatever you want. 08:22.900 --> 08:27.010 Then we need to provide the path to the file. 08:27.040 --> 08:27.460 Okay. 08:27.460 --> 08:31.780 So here from from there the path is to go to the source folder. 08:31.780 --> 08:33.850 And then my first node cpp. 08:34.360 --> 08:41.620 So we write src my first node dot cpp. 08:42.070 --> 08:44.980 So with this we create an executable. 08:44.980 --> 08:55.360 But we also need to add the dependencies for that executable with the payment target dependencies. 08:55.780 --> 08:58.390 Dependencies like that. 08:58.420 --> 08:58.870 Okay. 08:58.870 --> 09:05.800 So add executable is a command cmake function but that's specific to A-mount and Ros2 okay. 09:05.830 --> 09:08.320 So aim and target dependencies. 09:08.350 --> 09:12.130 The first argument is going to be the executable name. 09:12.130 --> 09:14.440 So cpp node. 09:14.440 --> 09:18.130 And then you will add all the dependencies that you need to link. 09:18.130 --> 09:24.040 So in this case you see in our code we are using rcl cpp. 09:24.280 --> 09:32.350 So I'm going to add Lclc-rp which is also found here we find package rcl cpp. 09:32.440 --> 09:38.950 If you don't add this then you will get an error at compilation saying that Lclc-rp is not found okay 09:38.980 --> 09:43.030 because you haven't used the payment target dependencies. 09:43.090 --> 09:43.630 Great. 09:43.630 --> 09:47.410 And this is going to create an executable, but it's not going to install it. 09:47.410 --> 09:51.550 So we need to add an install block okay. 09:51.580 --> 09:53.920 And in this you can write for example here. 09:53.920 --> 09:58.750 So let's write target like that uppercase. 09:59.440 --> 10:04.780 And then we're going to add I'm just adding two spaces here cpp node. 10:04.780 --> 10:06.580 That's the executable name. 10:06.580 --> 10:07.720 Same here. 10:08.080 --> 10:10.270 And then destination. 10:12.310 --> 10:13.390 All uppercase. 10:13.390 --> 10:15.730 We're going to use lib slash. 10:16.360 --> 10:20.920 And then you use dollar sign curly brackets like that. 10:20.920 --> 10:25.180 And project underscore name. 10:25.180 --> 10:27.430 And make sure you don't make any typo here. 10:27.430 --> 10:31.270 It's dollar sign curly brackets project name okay. 10:31.300 --> 10:33.400 Because I see lots of people making typos here. 10:33.400 --> 10:36.610 And then it doesn't work well because there is a typo okay. 10:36.640 --> 10:40.210 So this is going to create an executable with the dependencies. 10:40.210 --> 10:45.550 And this is going to install the executable in somewhere in the lib folder. 10:45.550 --> 10:48.460 So that's going to be in the install folder of the workspace. 10:48.460 --> 10:50.950 Somewhere in the package there's going to be a lib folder. 10:50.950 --> 10:54.250 And that's where we install the C plus plus executables. 10:54.250 --> 11:00.790 And note that this you just need to do it once because then for any new executable that you want to 11:00.820 --> 11:05.380 add from this package, you basically need to duplicate those two lines. 11:05.380 --> 11:11.620 And then you just need to add the new executable name in a new line just here. 11:11.650 --> 11:14.620 Okay, so let's save that. 11:14.650 --> 11:16.420 Make sure you save everything. 11:16.420 --> 11:17.650 All the files. 11:17.980 --> 11:19.750 Let's go back to the terminal. 11:19.780 --> 11:24.760 Let's go back to the Ros2 workspace once again. 11:24.790 --> 11:29.500 It's super important that you build from that folder and not anywhere else. 11:29.500 --> 11:31.510 And let's do a quick build. 11:32.050 --> 11:36.100 So we could build both packages because we have two packages. 11:36.130 --> 11:41.080 If you want you can just build with packages select. 11:41.170 --> 11:48.970 We can just build my CP pkg and let's use Autocompletion for everything because that makes it faster. 11:48.970 --> 11:52.450 And we don't have errors when we type stuff. 11:54.430 --> 11:54.730 All right. 11:54.730 --> 11:59.800 And you can see well if you have an cplusplus error that's what it's going to look like. 11:59.800 --> 12:02.890 So sometimes it can be explicit or not. 12:02.890 --> 12:05.140 But I need to go back to my file. 12:05.140 --> 12:10.740 And you see well actually I need to give a name here. 12:10.920 --> 12:13.890 So let's do CP test. 12:14.220 --> 12:14.760 All right. 12:14.760 --> 12:18.210 So you can see this kind of error is what you're going to get. 12:18.210 --> 12:25.950 So this is a here this is a typical classic C plus plus error that you see that when you build the package 12:25.950 --> 12:26.880 that's going to build the file. 12:26.880 --> 12:28.950 And that's when you have errors. 12:28.980 --> 12:29.400 Okay. 12:29.430 --> 12:32.340 So in this case we go back to the file here. 12:32.340 --> 12:36.990 When I create a node I need to pass the node name of course as a parameter. 12:36.990 --> 12:42.300 So I save again and then I build again. 12:44.970 --> 12:47.610 And you can see now successful. 12:47.610 --> 12:50.820 So you see this time here we have finished. 12:50.850 --> 12:53.100 Last time we had failed okay. 12:53.130 --> 12:55.770 So that's how you know that the package has been built. 12:55.770 --> 12:57.690 You see this finished line. 12:57.690 --> 12:58.200 Great. 12:58.200 --> 12:59.730 So what happened. 12:59.730 --> 13:05.100 What happened is that we have this file that is used here to create an executable. 13:05.400 --> 13:13.620 This executable is named CP node and is going to be installed somewhere inside the install folder of 13:13.620 --> 13:17.670 our workspace, so you can try to browse inside and find the file if you want. 13:17.670 --> 13:21.780 But it doesn't really matter because we are going to use Ros2 right now. 13:21.780 --> 13:24.330 So let's source the workspace. 13:24.360 --> 13:30.930 Let's do source install setup bash to make sure that we source the workspace, because we have added 13:30.930 --> 13:33.600 something in the terminal that's already open. 13:33.960 --> 13:39.300 And then let's do Ros2 so we can do it from here, from the home directory from anywhere. 13:39.510 --> 13:48.750 So let's do clear and Ros2 run my CP, let's press tab cp package. 13:48.750 --> 13:54.720 And then what was the name CP just in case you press tab is going to be found. 13:54.960 --> 13:57.450 Okay CP node let's press enter. 13:57.450 --> 13:59.730 And you see we have hello world. 13:59.730 --> 14:01.170 So we have the info log. 14:01.170 --> 14:02.430 We have the timestamp. 14:02.460 --> 14:05.190 That's the name of the node okay. 14:05.220 --> 14:06.270 And then the log. 14:06.900 --> 14:08.850 And once again here you see we have. 14:08.850 --> 14:12.630 So the name of the file is my first node DHCP. 14:13.890 --> 14:15.840 Okay, that's one thing. 14:15.870 --> 14:18.510 The second thing is the name of the node here. 14:18.510 --> 14:20.040 It's CP test. 14:20.040 --> 14:24.690 And the third thing is the name of the executable which is CP node. 14:24.690 --> 14:30.990 So you see those are three different things that sometimes you're going to use the same for all three. 14:30.990 --> 14:33.780 But they are three different things. 14:33.780 --> 14:35.430 And you can see it here. 14:35.460 --> 14:43.350 When we do raster run we actually use the executable name that we have created in the Cmakelists.txt. 14:43.350 --> 14:50.280 And then we see CP test in the log, because that corresponds to the node name that is defined from 14:50.280 --> 14:51.690 within the code. 14:51.780 --> 14:52.410 All right. 14:52.410 --> 15:00.420 And now well let's just finish this with a spin because you see once again I run this and that's it. 15:00.450 --> 15:05.130 It's going to start print something and then shut down. 15:05.340 --> 15:07.590 That's exactly what we asked it to do. 15:07.590 --> 15:10.380 But now let's say we want to keep the node alive okay. 15:10.410 --> 15:17.700 So the node can stay alive as long as we want until we press Ctrl C so we can do this right here just 15:17.700 --> 15:18.480 before shutdown. 15:18.480 --> 15:24.930 We do lclc-rp and then spin and we pass the node. 15:24.930 --> 15:28.200 You see, we need to give a shared pointer to a node. 15:28.200 --> 15:30.450 So we pass the node as a parameter. 15:30.450 --> 15:31.830 And that's basically it. 15:31.860 --> 15:36.600 So now I save and I need to build again okay. 15:36.600 --> 15:40.650 So I go back to my Ros2 workspace. 15:40.650 --> 15:46.680 And then you need to remember that every time that we change the code we're going to do build source 15:46.680 --> 15:47.610 and run. 15:47.610 --> 15:50.040 So let's find the command to build. 15:50.070 --> 15:51.210 It's here. 15:53.580 --> 16:03.240 So I have built now I will source and then I will run okay. 16:03.240 --> 16:08.250 And this time you see that we are hanging here because the node is spinning. 16:08.250 --> 16:12.930 Now I press Ctrl C and you see the node is shut down.