WEBVTT 00:00.050 --> 00:03.590 This is now step number four of this final project. 00:03.590 --> 00:05.180 And what do we have so far? 00:05.180 --> 00:12.560 Well, we have a turtle spawner node that will spawn turtles on the turtle SIM with random coordinates. 00:12.560 --> 00:16.010 And for now we spawn one new turtle every two seconds. 00:16.010 --> 00:20.180 Then we have a turtle controller node that will take the first turtle. 00:20.180 --> 00:21.830 So that's called turtle one. 00:21.830 --> 00:24.920 And it's going to make this turtle move to a target position. 00:24.920 --> 00:26.390 And what's the target position? 00:26.390 --> 00:31.580 Well, we are actually publishing a list of turtles that's going from the turtle spawner to the turtle 00:31.580 --> 00:32.390 controller. 00:32.390 --> 00:34.430 And we go to the first turtle. 00:34.430 --> 00:41.330 Now what's next to do is that first, when the master turtle reaches one turtle. 00:41.330 --> 00:44.780 So one target turtle, we should remove that turtle. 00:44.780 --> 00:48.080 So we should kill that turtle and remove it from the screen. 00:48.080 --> 00:53.060 And second, we need to give a new target to the master turtle. 00:53.060 --> 00:57.170 So it's going to go to the next turtle, etc., etc.. 00:57.200 --> 00:57.650 Okay. 00:57.680 --> 00:58.310 Let's. 00:58.310 --> 01:02.540 So I have the turtle sim node running here. 01:02.540 --> 01:04.970 I have the turtle controller here. 01:05.000 --> 01:10.910 Well, we just need the turtle sim here and let's just do a Ros2 service list. 01:11.450 --> 01:16.220 So you see, we have lots of services, but we have the kill service. 01:16.220 --> 01:18.290 That's the one that we want to use. 01:18.320 --> 01:24.800 Ros2 service type with kill. 01:25.130 --> 01:25.790 Okay. 01:25.790 --> 01:28.100 So you see it's total SIM service kill. 01:28.100 --> 01:30.620 So now I can do well actually. 01:30.650 --> 01:43.280 Ros2 interface show total sim save kill to see what's inside. 01:43.310 --> 01:45.260 And you see, it's pretty simple. 01:45.860 --> 01:49.610 We just give a name and we don't receive any response. 01:49.730 --> 01:52.910 Let's call it Ros to run. 01:53.180 --> 01:54.980 Actually, no Ros to service. 01:56.390 --> 02:02.820 Call With kill and then tethered SIM service kill. 02:02.970 --> 02:07.350 I will provide the request, which is name. 02:07.710 --> 02:10.500 And while we know this first turtle here. 02:10.500 --> 02:12.120 So that's the turtle one here. 02:12.120 --> 02:13.560 That's the master turtle. 02:13.560 --> 02:19.140 And this first turtle that was spawned is named turtle two. 02:19.170 --> 02:23.040 So if I run this, you see the turtle disappears. 02:23.040 --> 02:24.720 And we want to do that in the code. 02:24.750 --> 02:25.020 All right. 02:25.050 --> 02:27.900 So we will need to call this service from the code. 02:27.900 --> 02:29.430 And where do we call it. 02:29.460 --> 02:35.640 Well you could think we could call it directly from the turtle controller because we know we have reached 02:35.640 --> 02:36.420 the goal. 02:36.420 --> 02:40.410 We know what the position of the target turtle, we could remove it from here. 02:40.410 --> 02:47.850 But as we keep the list of alive turtles in the turtle spawner, it would be best actually to do everything 02:47.850 --> 02:49.950 that's related to what? 02:49.980 --> 02:56.040 Spawning and removing turtles from that node so that we can keep the list accurate. 02:56.040 --> 03:01.780 And then we just need to publish the new list, which is going to contain just the turtles that are 03:01.810 --> 03:03.910 actually spawned and not removed. 03:03.940 --> 03:08.920 And so what I'm going to do here, I'm going to create a service between the turtle controller and the 03:08.920 --> 03:10.060 turtle spawner. 03:10.090 --> 03:14.500 Here we're going to have a service server that's going to be called Catch Turtle. 03:14.500 --> 03:18.760 And whenever the turtle controller has reached you see target reached. 03:18.910 --> 03:24.520 We are going to use a service client to call the catch turtle service. 03:24.520 --> 03:31.450 And here when we receive a request then we can call the kill service of the turtle SIM node. 03:31.480 --> 03:31.900 All right. 03:31.900 --> 03:33.430 So that's what we want to do. 03:33.460 --> 03:36.280 And for that I'm going to create a new interface. 03:36.850 --> 03:37.870 I'm going to go to. 03:37.900 --> 03:45.310 So let's stop everything and let's go to my robot interfaces SRV. 03:45.670 --> 03:52.900 Because we're going to create an interface for a service and then touch I'm going to name it Catch turtle 03:52.930 --> 03:53.860 Dot SRV. 03:54.190 --> 03:56.950 So you could use an existing interface if you want. 03:56.980 --> 04:03.040 Here, I name it Catch Total and I'm going to design it specifically for this application that we want 04:03.040 --> 04:03.520 to do. 04:03.550 --> 04:03.820 Okay. 04:03.850 --> 04:05.260 Let's go to the code. 04:05.260 --> 04:08.890 In my robot interfaces in SV we have catch total. 04:08.890 --> 04:11.260 And the only thing we really need is the name. 04:11.260 --> 04:12.850 So I'm going to put string name. 04:12.880 --> 04:13.180 Okay. 04:13.210 --> 04:17.410 So the total controller is going to send the name of the turtle to the turtle spawner. 04:17.440 --> 04:19.240 Then we have three dashes. 04:19.240 --> 04:21.400 And do we need a response. 04:21.430 --> 04:26.290 Well not really I'm still going to put a bool success okay. 04:26.320 --> 04:28.450 Just in case we can return true or false. 04:28.450 --> 04:30.070 So I save this. 04:30.070 --> 04:31.330 Make sure you have the three dashes. 04:31.360 --> 04:32.680 That's very important. 04:32.770 --> 04:46.810 And then in List.txt I am just going to add my new service SV catch turtle.sv I save all of that and 04:46.810 --> 04:49.000 then let's build the interface. 04:50.110 --> 04:57.670 So Ros2 workspace click on build packages. 04:57.790 --> 05:03.100 Select with my robot interfaces. 05:05.500 --> 05:06.160 All right. 05:06.160 --> 05:08.140 And let's just verify. 05:08.170 --> 05:11.230 So let's source setup bash. 05:11.230 --> 05:20.110 And let's verify with Ros2 interface show my robot interfaces CV. 05:20.710 --> 05:23.320 And then let's use the Autocompletion. 05:23.380 --> 05:25.120 Do we find this. 05:26.440 --> 05:29.230 So yes we have catch total. 05:29.440 --> 05:29.860 Great. 05:29.860 --> 05:39.790 And now well once again I'm going to actually stop everything and also close VSCode and start everything 05:39.820 --> 05:40.720 again. 05:42.160 --> 05:46.900 And let's go to the workspace and open VSCode. 05:47.980 --> 05:54.460 So now we know VS code has been sourced with all the new interfaces we have built. 05:55.960 --> 05:56.320 All right. 05:56.320 --> 05:58.090 So I don't need that anymore. 05:58.120 --> 06:03.790 And as we create here a service, usually the best thing is to start from the server side. 06:03.790 --> 06:18.190 So let's import the interface from my robot interfaces dot save this time import catch turtle I'm going 06:18.220 --> 06:21.580 to create a service here. 06:22.510 --> 06:32.140 Self dot catch turtle service is equal to self dot. 06:33.190 --> 06:38.350 Create service with the catch turtle type. 06:38.410 --> 06:40.360 The name is going to be. 06:40.390 --> 06:43.570 Well let's name it simply Catch turtle. 06:43.600 --> 06:46.450 You see once again we use a verb catch. 06:46.660 --> 06:48.280 And then I need a callback. 06:48.280 --> 06:51.340 So let's add a callback here. 06:51.370 --> 06:52.820 The order it doesn't matter. 06:53.510 --> 06:54.650 Callback. 06:55.370 --> 06:56.300 Catch. 06:56.810 --> 06:57.710 Turtle. 06:59.930 --> 07:11.210 With self request is going to be catch turtle dot request and then response is going to be catch turtle 07:11.240 --> 07:13.670 dot response. 07:15.140 --> 07:27.560 What I can do is put my callback here self dot callback catch turtle and this on a new line. 07:27.560 --> 07:28.670 So it's a bit better. 07:28.700 --> 07:29.810 All right we have the service. 07:29.840 --> 07:30.770 We have the callback. 07:30.770 --> 07:32.240 What do we do in the callback. 07:32.240 --> 07:36.740 Well we are going to call the kill service from turtle SIM. 07:36.740 --> 07:42.800 So I'm going to put a comment here for now call kill service. 07:42.800 --> 07:44.840 Then we will need to return a response. 07:44.840 --> 07:47.990 So response dot success. 07:47.990 --> 07:53.450 I'm not going to do anything here really I'm going to just put true because we're going to call the 07:53.450 --> 07:53.960 service. 07:53.960 --> 07:57.590 But you could decide to wait until you get a response from the service. 07:57.590 --> 08:02.450 But anyway, you don't get any, uh, thing in the response of the kill service. 08:02.450 --> 08:05.780 So this boolean flag is not really useful. 08:05.810 --> 08:06.200 Okay. 08:06.230 --> 08:08.360 We are just using it because I created it. 08:08.360 --> 08:12.560 So let's just put true and return a response. 08:13.040 --> 08:13.370 All right. 08:13.400 --> 08:14.810 So that's for the catch total. 08:14.840 --> 08:17.840 Now here we need to call the kill service. 08:17.840 --> 08:30.080 So the kill service if I start total SIM again rose to run total sim total sim node okay. 08:30.110 --> 08:33.440 Let's just do a rose to service list. 08:33.950 --> 08:44.900 Rose to service type with kill and a rose to interface show with that one. 08:45.950 --> 08:48.710 So we have all the information we need okay. 08:48.740 --> 08:51.780 The name the type and what's inside the interface. 08:51.780 --> 08:54.570 So let's import that interface. 08:54.930 --> 09:03.990 I can put it here for example from turtle sim dot csv import kill. 09:04.050 --> 09:08.460 Just make sure I have everything in the package dot XML. 09:08.640 --> 09:11.730 And actually I forgot to do that before. 09:12.210 --> 09:14.610 You see we are using my robot interfaces. 09:14.610 --> 09:16.110 So I'm going to add a tag. 09:16.110 --> 09:22.470 Here depend my robot interfaces. 09:23.190 --> 09:27.870 Okay, so we have our CLP turtle SIM geometry messages and my robot interfaces. 09:27.870 --> 09:31.140 As you can see, the code was still running fine okay. 09:31.140 --> 09:39.300 This is mostly when you're going to do core code build in case this package is not built before you 09:39.330 --> 09:44.550 try to build the turtle sim catch them all package, then you're going to get an error. 09:44.640 --> 09:46.830 Okay, so that's why you add a depend tag here. 09:46.830 --> 09:48.930 For example for Python code. 09:48.960 --> 09:53.910 It's just to make sure that when you do call on build, all the packages here are found first. 09:53.940 --> 09:54.150 Great. 09:54.180 --> 09:56.370 So let's save that. 09:56.370 --> 09:59.610 And now where to call the kill service. 09:59.610 --> 10:02.730 That's going to be very similar to that. 10:02.730 --> 10:04.200 Call spawn service. 10:04.200 --> 10:08.220 We're going to do the same structure and the same structure here basically. 10:08.220 --> 10:10.590 So let's add a function here. 10:10.620 --> 10:17.400 Def call kill service self. 10:17.400 --> 10:21.720 We're going to put the turtle name and that's it. 10:21.750 --> 10:28.680 So actually if I call the service I need a service client I'm going to create a service client here. 10:28.680 --> 10:42.990 For example just after that one self dot kill client is equal to self create client with kill and name 10:42.990 --> 10:44.970 is slash kill. 10:45.000 --> 10:47.190 You can get that from the terminal. 10:50.220 --> 11:00.990 So in my method here I will do while not self dot kill client wait for service. 11:01.350 --> 11:04.740 Okay, I'm going quite fast here because we've done that already several times. 11:04.800 --> 11:07.920 And uh, let's just take that log. 11:07.980 --> 11:09.330 Wait for. 11:11.490 --> 11:12.600 Kill service. 11:12.630 --> 11:14.130 Even though we should never have this. 11:14.160 --> 11:16.440 If we start turtle sim first, you know. 11:16.470 --> 11:26.130 But just in case, it's a bit delayed so we can create the request, which is going to be a kill dot 11:26.130 --> 11:27.240 request. 11:27.240 --> 11:29.580 And in the request, we can do request. 11:29.610 --> 11:34.020 Dot name is equal to turtle name. 11:34.050 --> 11:38.460 That's the only thing we need to provide as you see here just the name. 11:39.510 --> 11:44.970 And then we can call the service. 11:44.970 --> 11:55.810 So I'm going to get future self dot kill client dot call async with the request. 11:56.020 --> 11:57.970 So it's always the same thing. 11:59.290 --> 12:04.060 And then let's add a future add done callback. 12:04.090 --> 12:11.560 I'm also going to use partial because I'm going to give the request to the callback because we need 12:11.560 --> 12:13.150 the name of the turtle. 12:13.330 --> 12:14.020 Okay. 12:14.020 --> 12:18.070 So before I write this let's write the callback. 12:18.100 --> 12:26.950 So callback call kill service will receive a future. 12:26.950 --> 12:34.420 And the request which is a kill dot request. 12:37.480 --> 12:39.160 Okay let's finish that. 12:39.160 --> 12:44.680 So partial self dot callback Kill. 12:44.920 --> 12:46.270 So callback call. 12:46.300 --> 12:51.970 Kill service and then request is equal to request. 12:52.000 --> 12:56.530 So the request parameter here is equal to the one we've created here. 12:57.970 --> 12:58.240 Okay. 12:58.270 --> 13:00.400 So nothing really new. 13:00.430 --> 13:03.880 It's always the same thing you see for this function. 13:03.880 --> 13:06.310 And then what do we do here. 13:06.340 --> 13:15.700 Well we don't really need to get the response because there is nothing and there is nothing in the response. 13:15.700 --> 13:21.580 So you could get the response object, but then you will not do anything with it. 13:21.580 --> 13:22.630 So that's it. 13:22.660 --> 13:28.150 When we get to this callback, basically we have the information that the service was executed. 13:28.180 --> 13:28.420 Okay. 13:28.450 --> 13:31.660 So we know the server has finished and is getting back to the client. 13:31.660 --> 13:34.660 So basically we know that the turtle was killed. 13:34.690 --> 13:34.900 Okay. 13:34.930 --> 13:38.890 If we provided a name that was valid, we know the turtle was killed. 13:38.890 --> 13:41.350 If the turtle is killed what do we want to do? 13:41.380 --> 13:48.200 We want to remove it from the list of alive turtles here. 13:48.230 --> 13:52.040 Okay, so when we spawn, we add a new one. 13:52.040 --> 13:56.570 But when we remove a turtle, we also remove it from that list. 13:56.570 --> 14:00.980 And what information we have here we have the information of the name. 14:00.980 --> 14:02.210 So we have the turtle name. 14:02.210 --> 14:09.230 So basically we can go through the turtle list and find turtles which correspond to that name and just 14:09.230 --> 14:10.100 remove it. 14:10.400 --> 14:22.520 I'm going to do four and I'm going to use I turtle in enumerate self alive turtles okay. 14:22.550 --> 14:25.790 So I use this because I will need the index. 14:25.820 --> 14:26.120 All right. 14:26.150 --> 14:32.420 So with this we get an element turtle and we get the index for each element in that list I can do if 14:32.450 --> 14:43.340 turtle dot name, which is each turtle we're going to go through is equal to request Dot name. 14:43.340 --> 14:47.750 So that's the turtle name we have provided here to the call kill service. 14:47.810 --> 14:54.290 And actually here to make it a bit more readable, instead of just passing the request, I could just 14:54.410 --> 14:55.430 pass. 14:55.670 --> 15:05.330 Turtle name and say that's the turtle name is equal to the well, the turtle name we get here. 15:05.360 --> 15:05.630 Okay. 15:05.660 --> 15:07.670 Just pass the same parameter name. 15:08.150 --> 15:11.480 We get it here, we pass it here, we receive it here. 15:11.480 --> 15:12.590 And I can say. 15:12.620 --> 15:13.760 Turtle name. 15:14.360 --> 15:14.660 All right. 15:14.660 --> 15:17.990 So if the turtle we go through each turtle in the array. 15:18.470 --> 15:19.640 If one of the turtle. 15:19.670 --> 15:26.120 Name corresponds to the turtle name we have sent to the kill service, then we know it's that turtle. 15:26.240 --> 15:36.050 And we can do, for example del to delete self dot live turtle with the index I okay, that's why I. 15:36.080 --> 15:37.040 Used the I here. 15:37.040 --> 15:37.880 And then what. 15:37.880 --> 15:42.830 I'm just going to add a break Because we just need to do this once. 15:42.830 --> 15:46.970 Once we find the turtle, we don't need to continue this loop. 15:47.120 --> 15:47.660 All right. 15:47.660 --> 15:50.900 And there's one more thing I'm going to do is I'm going to publish. 15:50.900 --> 15:58.910 So just before we break and we exit this callback, I'm going to do self dot publish a live turtles. 15:59.750 --> 16:00.590 Why is that. 16:00.590 --> 16:04.970 Because well now we have updated the list of turtles. 16:05.240 --> 16:09.200 So the array is not the same as it was just before the service. 16:09.200 --> 16:15.650 So I'm going to publish the new list and so that the turtle controller is going to receive the new list. 16:15.890 --> 16:16.280 All right. 16:16.280 --> 16:23.690 So by doing this you see in the turtle controller in the callback live turtles, whenever I receive 16:23.690 --> 16:27.920 the turtle list I just go to the first turtle. 16:27.920 --> 16:33.890 So if I remove one turtle and I publish the list again, then we're going to get a different list and 16:33.890 --> 16:35.930 we can get to another turtle. 16:35.960 --> 16:36.170 Okay. 16:36.200 --> 16:41.910 So by just doing this, it's going to take care of giving the turtle controller an updated list every 16:41.940 --> 16:44.070 time with the turtles to catch. 16:44.070 --> 16:49.110 So you see, we only publish when we spawn a new one and when we delete a new one. 16:49.110 --> 16:51.540 And let's just finish the code here. 16:51.540 --> 16:56.070 We need to actually call the kill service here. 16:56.070 --> 17:06.660 So self dot call kill service with the turtle name, which is going to be from the request dot name 17:06.930 --> 17:07.380 okay. 17:07.410 --> 17:10.110 From the catch turtle interface okay. 17:10.140 --> 17:12.090 So catch turtle we have a name. 17:12.780 --> 17:16.200 We basically forward this name to the kill service. 17:17.220 --> 17:17.490 All right. 17:17.520 --> 17:24.720 So what we did here very basically we created a catch turtle service that will basically forward to 17:24.720 --> 17:26.610 the kill service. 17:26.610 --> 17:28.680 So that's going to be a service client. 17:28.680 --> 17:29.970 We call the service. 17:29.970 --> 17:34.200 And when we get a response from the server we know the turtle has been removed. 17:34.200 --> 17:36.330 And we find the turtle from the list. 17:36.360 --> 17:38.940 We update the list and we publish a new list. 17:39.300 --> 17:44.970 And now we need to do the other side, which is the turtle controller, because who is going to call 17:44.970 --> 17:46.200 this catch turtle? 17:46.230 --> 17:46.500 Okay. 17:46.560 --> 17:48.030 Nobody is calling that for now. 17:48.030 --> 17:51.900 So we're going to create a service client in the turtle controller. 17:51.900 --> 17:55.680 And I'm going to create first here a method. 17:55.710 --> 17:58.650 Def call catch. 17:58.860 --> 18:06.120 Turtle service will just need to provide a turtle name. 18:06.720 --> 18:09.840 And I'm going to create a service client. 18:09.840 --> 18:16.680 So I'm going to create a service client here for example right here self dot catch. 18:16.740 --> 18:23.490 Turtle client is equal to self dot create client. 18:23.520 --> 18:34.140 I need the interface which is from my robot interfaces dot srv import catch turtle. 18:35.010 --> 18:37.270 All right I provide the interface here. 18:37.300 --> 18:42.700 Catch turtle and Servicename is is here. 18:42.730 --> 18:45.160 Catch turtle and make sure I use the same. 18:46.690 --> 18:49.120 Okay, now I can use this client. 18:50.380 --> 18:55.990 And actually I'm just going to take that code for example that one. 18:55.990 --> 19:04.270 I'm going to take all of that actually and put it there to show you that it's basically the same code. 19:04.450 --> 19:07.240 Just make sure to have the indentation. 19:07.630 --> 19:12.130 So it's not the kid client, it's catch turtle client okay. 19:12.160 --> 19:16.960 So why not, uh, client wait for service. 19:17.530 --> 19:22.450 We want waiting for catch turtle service. 19:22.450 --> 19:30.400 Then we create a request which is of type catch turtle dot request the request dot name. 19:30.400 --> 19:34.210 So it's also the same thing as for the kill here. 19:34.210 --> 19:35.650 It's also a name. 19:36.010 --> 19:37.570 Here we have a name attribute. 19:37.600 --> 19:44.860 A name field corresponds to the total name we do self dot catch total client call async. 19:44.890 --> 19:49.270 With the request we add a done callback with partial. 19:49.270 --> 19:55.420 So I'm going to add from func tools import partial. 19:58.240 --> 20:07.540 And it's going to be the actually callback I'm going to call it catch total. 20:09.820 --> 20:12.250 And I'm also going to pass the total name. 20:12.700 --> 20:12.970 All right. 20:12.970 --> 20:15.400 So you see the code is basically the same. 20:15.400 --> 20:16.720 We wait for the service. 20:16.750 --> 20:17.680 We create a request. 20:17.710 --> 20:18.820 We send the request. 20:18.850 --> 20:20.050 We add a callback. 20:20.050 --> 20:21.250 We add a callback. 20:21.250 --> 20:22.900 And what do we do in this callback. 20:22.900 --> 20:30.460 Well there's actually not much to do because the only thing we receive is well, a boolean. 20:30.460 --> 20:31.540 So success. 20:31.540 --> 20:34.180 You could just check maybe if Future. 20:34.180 --> 20:41.050 So we actually have the response which is a catch. 20:41.050 --> 20:49.120 Total response is equal to future dot result. 20:49.510 --> 21:00.520 You could say if not response dot success and then self dot get logger error. 21:01.060 --> 21:14.440 Uh, for example turtle could not be removed turtle plus turtle name and then could not be removed. 21:14.470 --> 21:15.190 Okay. 21:15.190 --> 21:22.030 So because you know that there is a success flag inside the response, you could handle that and just 21:22.030 --> 21:24.400 print the log in case something bad happens. 21:24.400 --> 21:29.830 We already know from the server side that, well, it's not going to happen. 21:29.830 --> 21:31.570 We just return true every time. 21:31.570 --> 21:34.040 But as the client, you don't necessarily know that. 21:34.040 --> 21:37.460 So you might just handle the error in case. 21:37.460 --> 21:42.590 But basically for this service client you could also have just done that okay. 21:42.620 --> 21:47.210 And just call the service and not really wait for any reply. 21:47.210 --> 21:49.580 But I'm going to do things completely here. 21:49.580 --> 21:54.530 And the only thing left to do is to call that function here. 21:54.530 --> 21:57.470 And when do we want to call that. 21:57.500 --> 22:01.820 Well when we have reached the target, you see we already have the code structure here. 22:01.820 --> 22:09.980 So after we reach the target I will do self dot call catch turtle service. 22:10.370 --> 22:12.530 And I need to provide the turtle name. 22:12.530 --> 22:13.760 What is the turtle name. 22:13.760 --> 22:25.520 Well we are actually chasing the turtle to catch so self dot turtle to catch dot name as simple as that. 22:25.520 --> 22:26.990 And then I'm going to do something else. 22:26.990 --> 22:32.270 I'm going to do self dot turtle to catch is equal to none. 22:32.270 --> 22:36.560 So I put back it to none because we don't need to send any more comments. 22:36.590 --> 22:41.150 Okay, we have reached the target turtle, so I just put it back to none. 22:41.150 --> 22:45.980 Which means that the next time we go to the control loop, you see, we're not going to do anything. 22:45.980 --> 22:47.150 We're just going to return. 22:47.150 --> 22:55.550 And then when we get a new array, we just get the first turtle that becomes the new turtle to catch. 22:55.550 --> 23:00.260 And we can continue to chase that turtle until we reach it. 23:00.290 --> 23:01.910 We call this service. 23:01.940 --> 23:04.550 It's going to kill the turtle on the turtle spawner. 23:04.580 --> 23:12.980 Send back the new array, and we can go back to this subscriber callback and chase a new turtle, etc. 23:13.010 --> 23:18.560 etc. as long as you have turtles on the screen, it's going to continue to chase turtles. 23:18.590 --> 23:21.890 All right, so the loop is kind of finished. 23:21.920 --> 23:24.620 Now we can test the code. 23:26.120 --> 23:30.990 So I am going to well I have the turtle sim node here. 23:31.980 --> 23:33.660 I'm just going to put that on the side. 23:36.120 --> 23:37.980 Keep the total SIM node here. 23:38.970 --> 23:47.520 And then I can start here across to run total sim. 23:48.660 --> 23:51.750 Catch them all with controller. 23:51.990 --> 23:55.560 So it should not print any error. 23:55.560 --> 23:56.130 It's working. 23:56.130 --> 24:01.710 The control loop is working but we don't have any turtle to chase, so nothing is happening. 24:01.710 --> 24:03.660 And then I'm going to start the spawner. 24:03.660 --> 24:12.240 So Ros to run turtle sim catch them all with the spawner and let's see what's going to happen. 24:13.650 --> 24:16.440 So we wait for one turtle to spawn. 24:16.440 --> 24:21.090 And you see, as soon as one turtle has spawned, we chase the turtle. 24:21.090 --> 24:24.360 Then the turtle disappears and then we chase another one. 24:25.470 --> 24:28.950 So you see, it is currently working.