WEBVTT 00:00.080 --> 00:04.940 This is the solution for the first challenge of the activity five on parameters. 00:04.940 --> 00:12.290 And what we want to do here is to come back to the robot news station node that we have created at the 00:12.290 --> 00:18.350 beginning of the course, and we want to be able to provide a different robot name at runtime. 00:18.350 --> 00:21.380 So you see this is hard coded in the code. 00:21.380 --> 00:21.980 For now. 00:21.980 --> 00:26.960 We want to be able to choose a different robot name when we start the node. 00:26.960 --> 00:33.170 And so for example it's going to say hi this is and then a different robot name plus from the robot 00:33.170 --> 00:34.070 news station. 00:34.070 --> 00:35.090 And how to do that. 00:35.120 --> 00:37.220 Well we're going to use a parameters. 00:37.730 --> 00:44.030 So I'm going to the beginning of the constructor here I have my super that I live. 00:44.030 --> 00:48.800 And then I'm going to do self declare parameter. 00:48.950 --> 00:53.630 And the name of the parameter I gave you is robot name. 00:53.960 --> 00:56.420 And I'm going to give it a default value. 00:56.420 --> 00:58.280 I'm going to use that one okay. 00:58.310 --> 01:00.590 That was the value I wanted to use in the code. 01:00.590 --> 01:03.440 So let's keep it as a default value. 01:03.830 --> 01:05.450 And now the robot name. 01:05.450 --> 01:10.370 Instead of just hard coding it, I will simply do self. 01:11.120 --> 01:22.700 So self dot get parameter with the value robot name it must be the same and dot value. 01:22.790 --> 01:24.530 Okay, once again very important. 01:24.530 --> 01:25.820 Don't add any parentheses. 01:25.820 --> 01:29.420 And you see that's basically all we need to change in the code. 01:29.420 --> 01:32.330 Because then we use the robot name variable here. 01:32.330 --> 01:36.140 So I've kind of already prepared the code in advance for that. 01:36.140 --> 01:40.940 If you had hard coded the name directly in the string, you should have. 01:40.940 --> 01:42.140 For example, like this. 01:42.140 --> 01:47.990 You create a attribute a class attribute, and you set the class attribute here with the value of the 01:47.990 --> 01:48.800 parameter. 01:49.100 --> 01:49.520 Okay. 01:49.520 --> 01:51.410 So with those two lines that's it. 01:51.920 --> 01:53.600 Now I'm going to save. 01:53.600 --> 01:57.170 And I think I used Simulink install before. 01:57.170 --> 02:00.200 So we don't need to compile this again. 02:00.230 --> 02:08.870 Let's do Ros2 run my pip pkg with I think it was robot new station to execute table. 02:09.940 --> 02:11.710 Okay, so it's starting. 02:11.710 --> 02:14.560 We haven't provided any value for the parameters. 02:14.560 --> 02:18.370 Let's see with Ros2 param list. 02:19.930 --> 02:20.320 Okay. 02:20.350 --> 02:23.140 And you can see we have a robot name. 02:23.170 --> 02:31.240 If I do Ros2 param get robot new station and robot name. 02:33.250 --> 02:41.890 This is a string and the value is C-3po, just like we have here with the default value. 02:42.550 --> 02:49.840 Then if I do ros two topics, let's do Ros two topic list and the name was Robot News. 02:49.990 --> 02:54.220 Ros two topic equal robot news. 02:56.050 --> 02:56.620 We see. 02:56.650 --> 02:59.590 Hi, this is C-3po from the robot news station. 02:59.620 --> 02:59.980 All right. 03:00.010 --> 03:03.460 So now let's stop this and let's run it again. 03:03.460 --> 03:09.370 But this time I'm going to provide a parameter ros args dash p. 03:09.370 --> 03:14.380 And then the name of the parameter is robot name exactly? 03:14.530 --> 03:17.860 And let's say a b, c. 03:19.960 --> 03:20.290 Okay. 03:20.320 --> 03:21.460 It's starting. 03:21.460 --> 03:23.680 And we can see directly with the topic. 03:24.430 --> 03:27.940 We have hi, this is ABC from the robot News station. 03:27.940 --> 03:32.080 And we can get the parameter ABC. 03:32.290 --> 03:32.710 All right. 03:32.740 --> 03:35.710 So it's working now if you want to add. 03:35.710 --> 03:39.160 So if you want to add a space in a string. 03:39.160 --> 03:43.120 So let's say the name of the robot is the robot. 03:43.150 --> 03:49.750 If you want to add a space where that's not going to work you need to add double quotes okay. 03:51.640 --> 04:00.220 And here you see we have the robot and the parameter value is that one you see. 04:00.220 --> 04:03.610 So you just add double quotes if you want to add a space. 04:03.610 --> 04:03.970 Great. 04:03.970 --> 04:08.590 And now well I'm gonna start this node. 04:08.620 --> 04:17.830 Let's for example rename it dash R and then node and let's name it two. 04:17.860 --> 04:21.400 So that was robot new station, let's say station one. 04:23.230 --> 04:23.530 Okay. 04:23.530 --> 04:25.450 So it's station one and it's publishing. 04:25.450 --> 04:30.430 Note that I start kind of always with renaming Remappings and then parameters. 04:30.430 --> 04:34.630 You don't have to follow that order, but I think it makes things a bit cleaner. 04:34.630 --> 04:35.860 So I have this note here. 04:35.860 --> 04:45.760 Let's start another node here Ros two run my pi pkg robot new station. 04:46.390 --> 04:57.760 Let's rename let's say station two and then dash p robot name. 04:58.870 --> 05:03.790 And that's going to be discard for example. 05:04.120 --> 05:07.720 And okay we have station two. 05:07.750 --> 05:15.970 If I look at what we get on the robot news topic you see then we get both okay. 05:16.000 --> 05:18.580 Because both are publishers to that node. 05:18.580 --> 05:20.710 And so everything is correctly working. 05:20.710 --> 05:22.590 Just one last thing I want to show you. 05:22.590 --> 05:32.040 If I do Ros2 param list, then you see we have those two nodes and each node has a different set of 05:32.040 --> 05:32.940 parameters. 05:32.970 --> 05:33.330 Okay. 05:33.360 --> 05:40.560 If I do ros2 param get station one with robot name. 05:40.740 --> 05:45.120 So somehow well you see that it's a bit stuck. 05:45.120 --> 05:47.340 So autocompletion with parameters. 05:47.340 --> 05:55.020 Sometimes it's stuck so well okay, it's still a bit buggy, so I recommend just you copy paste the 05:55.020 --> 05:56.370 parameters like that. 05:56.940 --> 06:04.290 And what I wanted to show you is that for those two nodes you see those two parameters have different 06:04.290 --> 06:04.860 value. 06:04.860 --> 06:12.000 So the robot name parameter here only exists within that node and has a different value than that one 06:12.030 --> 06:12.390 okay. 06:12.420 --> 06:16.530 So if you kill that node it's going to kill that parameter inside this node okay. 06:16.560 --> 06:17.640 They have the same name. 06:17.640 --> 06:25.710 But you can see they each belong to a different node and they only exist as long as the node exists.