WEBVTT 00:00.080 --> 00:05.390 And now let's integrate this service client inside a node that uses OOP. 00:05.480 --> 00:09.590 That first example here was great to start working with service clients. 00:09.590 --> 00:15.620 And you can use this exact code as a template whenever you want to quickly test a service server that 00:15.620 --> 00:17.030 you have just written. 00:17.060 --> 00:23.930 Now as you can see, if we want to add this inside a node that uses object oriented programming, well, 00:23.930 --> 00:28.250 if I come back to the template, you see we make the node spin okay. 00:28.280 --> 00:32.300 And in this script we have a spin until future complete. 00:32.300 --> 00:38.870 So if we use that we are basically going to make a node spin while it is already spinning. 00:38.870 --> 00:41.510 And that can lead to very weird behaviors. 00:41.510 --> 00:43.400 So we are not going to use that. 00:43.400 --> 00:46.310 And I'm going to show you how to solve that challenge right now. 00:46.310 --> 00:49.670 So let's create a new file okay. 00:50.180 --> 00:55.940 Let's go back to Ros2 workspace Source Python package. 00:56.150 --> 01:00.170 And let's create a add. 01:01.270 --> 01:04.090 to its client. 01:04.090 --> 01:06.670 So this one is just going to be the add to its client. 01:06.700 --> 01:07.270 Okay. 01:07.300 --> 01:11.410 With the normal OOP node dot p y. 01:11.530 --> 01:13.570 And let's make it executable. 01:15.400 --> 01:18.400 Add to its client dot p y. 01:18.850 --> 01:22.870 Okay let's take the template. 01:23.470 --> 01:25.810 And let's go to the client. 01:25.810 --> 01:28.120 And let's use this template this time. 01:28.120 --> 01:33.400 And let's call it add to int client. 01:34.810 --> 01:35.440 Okay. 01:35.440 --> 01:40.300 And add to int client. 01:42.520 --> 01:47.680 Let's remove those and remove the column here. 01:47.710 --> 01:48.190 Okay. 01:48.220 --> 01:55.120 So first things first before we even create the service client we need to import the interface. 01:55.150 --> 01:57.790 And the interface is going to be the same okay. 01:57.970 --> 01:59.020 From the server. 01:59.020 --> 02:07.920 a sort from example interfaces dot csv import add to ints. 02:07.950 --> 02:10.020 Okay, we have that interface. 02:10.020 --> 02:16.020 And now what I'm going to do is I'm going to do the first step which is to create a service client. 02:16.020 --> 02:19.980 I'm going to do that in the constructor self dot. 02:20.100 --> 02:32.880 Let's name it client is equal to self create client with add to int and add two ints okay. 02:32.910 --> 02:34.950 So that's the same thing. 02:34.950 --> 02:38.400 Here we provide the type and the name. 02:38.430 --> 02:39.690 Make sure it's the same. 02:39.690 --> 02:44.310 But this time you see we use self because we are directly inside the node class. 02:44.310 --> 02:50.010 So this is a node we can use self and we store that as an attribute of the class. 02:50.010 --> 02:55.860 Then what I will do is I will create a method that we will use to call the service to send the request. 02:55.890 --> 03:01.420 Let's name this call Add two ints, for example. 03:01.420 --> 03:04.750 So call and then the name of the service self. 03:04.750 --> 03:08.710 And let's say we are going to give a and b okay. 03:08.740 --> 03:11.710 So to match the a and b in the request. 03:11.950 --> 03:19.390 And in this method what I will do is well before I send the request, I will first make sure that you 03:19.390 --> 03:21.700 see the service is up. 03:21.700 --> 03:26.830 So I can just take that line here and use it right here. 03:27.310 --> 03:29.590 And let's put the correct indentation. 03:29.590 --> 03:31.270 And you see we need to replace stuff. 03:31.270 --> 03:35.830 So it's not client it's self client. 03:36.370 --> 03:37.810 That's the one we've created here. 03:37.810 --> 03:41.470 And the node is not just node it's self all right. 03:41.500 --> 03:42.730 But the code stays the same. 03:42.730 --> 03:45.460 So we create the client here in the constructor. 03:45.460 --> 03:50.680 And then in this method that we're going to call later we first wait for the service. 03:50.710 --> 03:52.210 We make sure that it's up. 03:52.210 --> 03:55.090 After that we can create a request. 03:55.090 --> 03:59.220 So to create a request well we use the same code. 03:59.610 --> 04:02.850 So I'm just going to take that code here and put it there. 04:05.430 --> 04:05.850 Okay. 04:05.850 --> 04:10.950 We create a request which is an add to insert request. 04:10.950 --> 04:15.960 And we give some numbers request a and request dot b. 04:15.990 --> 04:21.030 The next step is to send the request how to send the request. 04:21.060 --> 04:28.860 We do self client call async with the request. 04:28.890 --> 04:30.480 Okay so nothing new here. 04:30.480 --> 04:31.710 That's the same thing we did. 04:31.710 --> 04:34.200 And this is going to give us a future. 04:34.200 --> 04:35.970 So we save it as a future. 04:35.970 --> 04:38.700 And then this is the big difference. 04:38.700 --> 04:42.450 We are not going to do a spin inside the spin. 04:42.450 --> 04:44.610 We are not going to spin while we are spinning. 04:44.610 --> 04:50.250 What I'm going to do is I'm going to do future dot add done callback. 04:50.280 --> 04:57.470 You see we have add done callback and I will create a callback function that will be called when the 04:57.470 --> 05:00.020 client receives the response, okay. 05:00.020 --> 05:02.510 And that's going to work because the node is spinning. 05:02.510 --> 05:07.790 So if the node is spinning, we can execute all of the callbacks for this node including that one. 05:07.790 --> 05:13.910 So let's do callback call add to insert for example. 05:13.910 --> 05:16.190 That's the callback for this method here. 05:16.190 --> 05:17.510 What do we receive. 05:17.510 --> 05:20.690 So we have self and then we receive future. 05:20.960 --> 05:24.380 All right so you can register I'm just going to put. 05:24.380 --> 05:25.670 So I'm going to put pass. 05:25.670 --> 05:26.450 If you don't know pass. 05:26.450 --> 05:29.090 It just means you don't want to do anything in a function. 05:29.090 --> 05:31.430 So here just useful. 05:31.430 --> 05:33.530 So we don't have an errors in VS code. 05:33.530 --> 05:41.780 For now I'm going to do future dot add done callback and I'm going to provide self callback call add 05:41.810 --> 05:42.530 to ints. 05:42.560 --> 05:42.920 All right. 05:42.920 --> 05:45.350 So here I wait for the service. 05:45.350 --> 05:46.520 I create the request. 05:46.520 --> 05:48.770 I send the request asynchronously. 05:48.770 --> 05:51.710 And then I add a callback for when we get the response. 05:51.710 --> 05:54.650 So when we get the response we go to this code. 05:54.650 --> 06:01.180 And we can do response is equal to future dot result. 06:01.540 --> 06:13.930 And then we can do uh, not print but self getlogger for example.info let's say got response. 06:14.410 --> 06:16.660 It's going to be the same plus. 06:16.660 --> 06:22.120 So let's cast as a string response dot sum okay. 06:22.150 --> 06:26.290 We get the response object inside the response object we have the sum. 06:26.320 --> 06:26.770 All right. 06:26.770 --> 06:29.560 And now there's just one thing that's missing. 06:29.590 --> 06:32.350 Because if we start this node well we're going to start the client. 06:32.350 --> 06:37.420 But then no request is going to be sent because we don't call this function. 06:37.420 --> 06:42.700 So what I'm going to do in the main I'm going to create the node. 06:42.730 --> 06:44.020 So it's going to create the client. 06:44.020 --> 06:48.940 And then I'm going to do node dot call add to ints. 06:48.970 --> 06:52.390 I'm going to call this function right away with. 06:52.420 --> 06:55.210 So let's say actually here I put three and eight. 06:55.210 --> 06:59.150 But it's going to be A and B. 06:59.180 --> 07:02.420 Those are the parameters that I get from the method here. 07:02.450 --> 07:04.490 Let's say two and seven. 07:04.820 --> 07:10.160 And so what's going to happen here when we create the node it's going to create the client then. 07:10.160 --> 07:12.530 Well you could call that from anywhere. 07:12.530 --> 07:14.630 But here we don't have other callbacks for now. 07:14.630 --> 07:17.000 So I'm just calling it here. 07:17.030 --> 07:18.860 So that's going to wait for the service. 07:18.860 --> 07:25.880 Create a request, send a request and then register a callback so that when we get the response we can 07:25.880 --> 07:29.270 get it in this callback method after that. 07:29.270 --> 07:33.950 So we're going to execute this return here make the node spin. 07:33.950 --> 07:36.590 So the node is spinning and can execute the callbacks. 07:36.590 --> 07:42.620 That's why when we get the response from the server we can get to that part okay. 07:42.650 --> 07:46.640 So the node needs to be spinning in order to receive the response. 07:46.640 --> 07:52.640 And here well as I told you, if we had let's say a subscriber callback or if we had a timer callback, 07:52.640 --> 07:56.600 we could decide at some point to call this one from one of those callbacks. 07:56.600 --> 08:00.020 But because I don't have this here, I just call it here. 08:00.020 --> 08:01.280 It's going to be the same. 08:01.280 --> 08:05.690 Now let's save this and let's go back to the setup.py. 08:05.690 --> 08:18.230 And let's add the last executable here, add to its client which is going to be my pi pkg dot add to 08:18.260 --> 08:20.120 its client. 08:20.180 --> 08:22.250 And that's the main function. 08:22.250 --> 08:22.760 Great. 08:22.760 --> 08:24.230 Let's go back here. 08:24.230 --> 08:29.720 Let's go to the roster workspace and call call build. 08:29.720 --> 08:39.980 So if I go back here I can find call build with the Python package and symlink install okay let's open 08:39.980 --> 08:41.210 some terminals. 08:43.430 --> 08:46.250 I'm going to start a server here. 08:46.250 --> 08:55.320 So ros2 run my pi pkg with add to intz server Okay. 08:55.320 --> 09:04.650 And then I'm going to start the client Ros to run my Pi PG with add two ints client. 09:04.650 --> 09:07.620 So this time you see I can choose between client. 09:07.650 --> 09:08.400 No OOP. 09:08.430 --> 09:09.660 That's the previous script. 09:09.660 --> 09:11.790 And that one is the one we have just written. 09:11.790 --> 09:17.790 So I'm going to run the latest and you can see it's working. 09:18.000 --> 09:21.990 We have the log on the server side and the log on the client side. 09:22.020 --> 09:25.050 Now let's say we also want to. 09:25.080 --> 09:27.960 So here you see in this no. 09:27.990 --> 09:28.470 Where is it. 09:28.500 --> 09:33.690 Here in this callback I only get access to the response okay. 09:33.690 --> 09:40.590 If I wanted to print a plus B is equal to sum I could pass for example the request here. 09:40.590 --> 09:43.860 So I could put request. 09:43.860 --> 09:49.770 And then here I would need to do request is equal to request. 09:49.860 --> 09:55.040 So then I can pass the request object also in the callback. 09:55.040 --> 09:57.620 So we get access to what was the previous request. 09:57.620 --> 10:01.910 And in this case that request corresponds to that name here. 10:01.910 --> 10:03.830 And this is the object we've created. 10:03.830 --> 10:07.130 I'm just going to save and see if we get an error here. 10:07.760 --> 10:09.200 So let's start again. 10:10.520 --> 10:12.410 And you see we have an error okay. 10:12.410 --> 10:19.430 Because the future add on callback got an unexpected keyword argument because you've added an extra 10:19.460 --> 10:20.330 argument here. 10:20.330 --> 10:26.270 So you need to use the partial function from func tools okay. 10:26.300 --> 10:28.700 That's something specific to Python. 10:28.700 --> 10:32.120 You cannot really know that without having looked on the internet. 10:32.120 --> 10:36.470 So I'm going to import well for example here from Func tools. 10:36.470 --> 10:40.730 That's a Python module import partial. 10:40.730 --> 10:50.570 And then when you do add on callback you need to do partial here partial of that okay. 10:50.600 --> 10:56.790 So just remember that if you want to add extra arguments to a callback with add on callback for a future 10:56.790 --> 11:01.530 object, you need to add the partial function here from func tools. 11:01.530 --> 11:05.160 And let's just go back to new line here, because it takes a lot of space. 11:05.190 --> 11:11.250 Now let's save and that should work okay it's working. 11:11.250 --> 11:15.840 So now that it's working we can use the request here. 11:15.840 --> 11:19.380 And let's just do the same thing we did before here. 11:19.380 --> 11:21.750 Let's print that. 11:21.750 --> 11:26.400 So let's take this log and let's print that instead. 11:27.360 --> 11:30.150 It's going to be self okay. 11:30.150 --> 11:32.760 So we print the full equation. 11:32.760 --> 11:34.020 Let's save. 11:34.020 --> 11:37.110 And now I'm gonna run again. 11:37.140 --> 11:38.550 Let's see if it works. 11:39.840 --> 11:43.080 And you see we have the two plus seven is equal to nine. 11:43.080 --> 11:47.520 So in the callback we have the response. 11:47.520 --> 11:50.400 But we can also pass the requests okay. 11:50.430 --> 11:53.030 To know what was the request fields? 11:53.060 --> 11:53.570 Great. 11:53.570 --> 12:00.500 And the last thing we can do as a test is, well, we just call the function once, but let's call it 12:00.530 --> 12:02.570 actually three times. 12:02.600 --> 12:04.340 I'm going to use different numbers. 12:04.340 --> 12:10.610 So one plus four and then maybe ten plus 20. 12:11.090 --> 12:12.860 Okay let's save. 12:12.860 --> 12:15.470 And let's see what happens if we call it three times. 12:16.790 --> 12:18.500 Um let's run that here. 12:21.650 --> 12:23.360 You can see that it's working. 12:23.390 --> 12:23.630 Okay. 12:23.660 --> 12:26.510 We can send as many requests as we want. 12:26.540 --> 12:29.180 You can see it's going to process all three requests. 12:29.180 --> 12:32.000 So it's going to process them one by one. 12:32.000 --> 12:33.830 But you can see here it was very fast. 12:33.830 --> 12:35.690 So it looks like it's at the same time. 12:35.690 --> 12:37.700 And then for each request it's going to send back. 12:37.700 --> 12:40.670 So the server is going to send back the response to the client. 12:40.700 --> 12:41.030 All right. 12:41.030 --> 12:46.580 So with one client you can send several requests as you want. 12:46.610 --> 12:47.060 Great. 12:47.060 --> 12:52.130 And you have successfully written a full Python service server and client.