WEBVTT 0 00:00.450 --> 00:07.140 If you got stuck or if you had any problems completing this project, the first port of call is to review 1 00:07.140 --> 00:08.380 the lessons you learned today. 2 00:08.760 --> 00:14.280 It might just be that you need to see some of the theory a few more times and listen to it a few more 3 00:14.280 --> 00:19.410 times and practice it a few more times before you're ready to tackle this final challenge. 4 00:20.070 --> 00:24.660 But if you have completed it and you just want to see the solution, then I'm going to go through it 5 00:24.660 --> 00:25.380 with you right now. 6 00:26.400 --> 00:30.210 Again, we're going to complete all of the program requirements step by step. 7 00:30.570 --> 00:38.610 So the first thing is to print a report for all of the current resources in the coffee machine. Back 8 00:38.610 --> 00:39.090 in PyCharm, 9 00:39.330 --> 00:44.310 I'm actually going to collapse this entire project folder because I'm not going to be writing any code 10 00:44.310 --> 00:46.140 other than inside main.py. 11 00:47.040 --> 00:54.270 Now you can see up here, we've got access to four classes. And if we take a look inside the documentation, 12 00:54.480 --> 01:00.990 you can see that both the coffeemaker class and the money machine class have a method called report. 13 01:01.560 --> 01:06.690 And this is going to print a report of all of the resources like water, milk, coffee, 14 01:06.990 --> 01:09.810 and this is going to print a report of the current profit. 15 01:10.260 --> 01:16.290 So our final report is going to be both a report from the money machine as well as the coffee maker. 16 01:17.310 --> 01:22.380 Let's go ahead and start off by creating some objects from these classes. 17 01:22.950 --> 01:27.840 For example, the money machine is going to be just called money_machine 18 01:27.870 --> 01:30.250 or you could call it my_money_machine. 19 01:30.270 --> 01:33.090 You can actually name your objects anything you like. 20 01:33.720 --> 01:41.160 But I'm just going to use the default Python snake case to create a new variable money_machine, which 21 01:41.160 --> 01:46.980 is going to hold my object. And my object is going to be created, of course, from the money machine 22 01:46.980 --> 01:47.520 class. 23 01:48.090 --> 01:51.900 And the construction happens when I add the parentheses. 24 01:52.500 --> 01:58.440 So now I have a object created and stored inside this variable money_machine. 25 01:59.280 --> 02:06.870 Now, if I want this money machine to create a report, then all I have to do is tap into the object 26 02:07.260 --> 02:12.360 and then write a dot and then call the method that I need, which is report. 27 02:13.020 --> 02:15.630 So now if I go ahead and run my code, 28 02:18.360 --> 02:22.110 you can see it prints out the current amount of money in the machine. 29 02:22.890 --> 02:25.710 Now let's do the same thing for our coffee maker. 30 02:26.630 --> 02:31.010 Again, I'm going to call it coffee_maker, and you see this frequently. 31 02:31.020 --> 02:39.840 The object naming tends to be the lower case and snake case, so separated by underscores, version of the 32 02:39.840 --> 02:40.740 name of the class. 33 02:40.950 --> 02:47.580 So the name of the class is CoffeeMaker, and usually you'll see people name the object exactly the 34 02:47.580 --> 02:49.290 same, but in lowercase. 35 02:50.280 --> 02:57.900 And now that I have my coffee _maker, then I can go ahead and call the report method on that object 36 02:57.900 --> 02:58.410 as well. 37 02:58.800 --> 03:04.980 And now, if I run my code once more, you can see that I've got everything now being reported and printed 38 03:04.980 --> 03:05.190 out. 39 03:06.060 --> 03:12.870 So in this case, we don't actually have to care how report is implementing all of this functionality. 40 03:13.200 --> 03:19.470 All we have to do is read the documentation, find the method that does the thing that we want, and 41 03:19.470 --> 03:23.640 then trust that it will carry out the functionality as described. 42 03:24.870 --> 03:30.480 Now that we've completed step 1, the next one is to check that resources are sufficient. 43 03:31.080 --> 03:35.370 My first port of call is going to be going over to the documentation. 44 03:35.820 --> 03:42.240 And you can see that the coffeemaker class actually has a method called is _resource_efficient. 45 03:42.600 --> 03:50.130 And all we have to do is pass in the drink, which is a menu item, and then it's going to check and 46 03:50.130 --> 03:56.640 give us true, if that drink order can be made, and false if the ingredients are insufficient. 47 03:57.840 --> 04:03.930 So how do we get hold of this drink menu item to pass over to this method? 48 04:04.650 --> 04:11.700 Well, if we take a look at the menu class, you can see it has a method called get_items and this is 49 04:11.700 --> 04:15.030 where you really see reading the documentation properly, 50 04:15.450 --> 04:19.800 actually absorbing everything that's in here becomes really, really helpful. 51 04:20.460 --> 04:24.570 This menu class has two methods that are really useful. 52 04:25.050 --> 04:30.870 One, It's able to get a hold of the names of all the items that are available on the menu. 53 04:31.350 --> 04:35.370 And it returns it as a string separated by forward slashes. 54 04:36.120 --> 04:40.560 It's also able to find a drink based on the order name. 55 04:40.590 --> 04:47.550 So if we passed in one of these names to this function find_drink, then it's going to return a menu 56 04:47.550 --> 04:49.770 item object if it actually exists. 57 04:50.040 --> 04:51.990 Otherwise, it's going to return none. 58 04:52.620 --> 04:56.670 We're going to need both of these in order to ask the user what they want. 59 04:57.530 --> 05:02.520 Let's go ahead and set up our while loop. As we had previously 60 05:02.540 --> 05:08.660 I'm going to create a new variable called is_on and it's going to start off being true. 61 05:09.230 --> 05:16.880 And then while coffee machine is on, well then we're going to get hold of all the options that we 62 05:16.880 --> 05:22.850 can offer the user. And we get that by calling that method get_items. 63 05:23.300 --> 05:28.580 But of course, because this is a method, it's associated with an object. 64 05:28.670 --> 05:32.240 So we have to create an object from this menu blueprint. 65 05:33.440 --> 05:36.770 So let's do that next to all the other objects being created. 66 05:37.190 --> 05:42.050 So let's create a menu object and it's going to be created from the menu class, 67 05:42.050 --> 05:43.640 and then we add the parentheses. 68 05:44.030 --> 05:47.840 And now we have access to that object by the name menu. 69 05:48.380 --> 05:54.800 The options are going to be equal to the menu object and then we're going to call the get_items method. 70 05:55.340 --> 06:01.580 And then when this method returns, it's going to save the string and all the options into this variable 71 06:01.580 --> 06:02.390 called options. 72 06:02.990 --> 06:09.800 Now we can get the user's choice by asking them for what would you like? 73 06:11.170 --> 06:17.650 And then inside a set of parenthesis we'll offer them all the options. And then, of course, I need 74 06:17.650 --> 06:19.480 to turn this into an fstring. 75 06:19.630 --> 06:24.070 And the code highlighting immediately tells me that this is actually now working. 76 06:24.640 --> 06:32.740 So once I've got the user's choice, then I can incorporate the reporting behaviour into this choice. 77 06:33.130 --> 06:42.310 Remember, previously we said if the choice was equal to off, then that means the is_on is going 78 06:42.310 --> 06:45.390 to be equal to false, and elif 79 06:45.400 --> 06:47.860 the choice is equal to report, 80 06:48.310 --> 06:53.110 well, in this case, we're going to get the coffeemaker and the money machine to make their reports 81 06:53.110 --> 06:54.040 into the console. 82 06:54.970 --> 07:03.040 Finally, we're ready to tackle the next problem, which is how do we check that we have enough resources? 83 07:04.100 --> 07:10.520 And this is going to require us to find the drink given the order name that the user chose from the 84 07:10.520 --> 07:17.440 choice and then get hold of the menu item which comes as the output from this method call. 85 07:18.430 --> 07:26.110 So else, we're going to save our drink as a variable called drink, and then we're going to tap into 86 07:26.110 --> 07:35.500 the menu.find_drink. And find_drink, you'll notice, takes a order name as the input. 87 07:35.980 --> 07:42.370 So this is a string and this is going to be equal to whatever the user chose inside this choice. 88 07:42.940 --> 07:45.910 So let's put the choice in here as the input. 89 07:46.450 --> 07:51.190 And now, once we've got hold of this drink, let's go ahead and print it. 90 07:51.820 --> 07:55.930 Remember, we're expecting a menu item object at this stage. 91 07:56.500 --> 08:01.480 So let's click run, and let's make sure that we can hit report to get the report, 92 08:01.870 --> 08:11.440 we can say off to switch off the machine and exit the code, and we can also get hold of a latte by 93 08:11.440 --> 08:14.530 passing in latte as the drink that we want. 94 08:15.040 --> 08:21.940 And we now get printed a menu item object at this particular location in the computer's memory. 95 08:22.450 --> 08:23.040 Perfect. 96 08:23.050 --> 08:25.330 Everything is working as expected. 97 08:26.140 --> 08:32.590 Now, instead of printing the drink, I'm going to tackle this step 2, which is to check that the 98 08:32.590 --> 08:34.330 resources are sufficient. 99 08:35.440 --> 08:42.400 Again, that's going to require us to look through our documentation. And you'll see that the coffee 100 08:42.400 --> 08:43.600 maker class has 101 08:43.600 --> 08:50.260 that method is_resource _sufficient, and it expects a menu item object as the input. 102 08:50.710 --> 08:54.970 And then it's going to return true when it can be made and false if it can't. 103 08:55.960 --> 09:03.550 So let's get hold of our coffee maker object and then get it to check if the resources are sufficient 104 09:03.940 --> 09:07.000 to make the current drink that we're interested in. 105 09:07.870 --> 09:11.770 And let's go ahead and print the results here 106 09:12.820 --> 09:14.350 and run our code. 107 09:15.190 --> 09:23.290 Let's say that we wanted to make a latte. That's going to be resource sufficient, so true. Espresso, 108 09:23.620 --> 09:27.560 also true, and a Cappuccino is also true. 109 09:27.580 --> 09:29.740 So we can make all three drinks, basically. 110 09:30.070 --> 09:37.480 Now, instead of printing this, what we want to do is we want to check if this is true and then proceed 111 09:37.480 --> 09:40.210 to the next step if there are enough resources. 112 09:40.870 --> 09:47.830 Now the next step is to take payment from the user and to process the coins and check the transaction 113 09:47.830 --> 09:48.700 is successful. 114 09:49.630 --> 09:56.980 Notice how in our coffee machine documentation for the money machine, we don't actually have a way 115 09:56.980 --> 10:05.050 of processing the coins. But it what it does have is it allows us to make payments passing in the cost 116 10:05.050 --> 10:11.530 of the drink and then it will return true when the payment is accepted or false, if insufficient. 117 10:12.160 --> 10:15.650 So let's see what happens if we actually try to make payment. 118 10:16.510 --> 10:23.110 Let's tap into our money machine object and then call the make_payment method and we have to pass in 119 10:23.110 --> 10:26.170 the cost of the drink that the user ordered. 120 10:26.710 --> 10:34.480 So we've got the drink object here, which remember is a menu item, and each of the menu items have 121 10:34.480 --> 10:39.880 three attributes that we care about: the name of the drink, the cost of the drink and the ingredient 122 10:39.880 --> 10:40.240 list. 123 10:40.630 --> 10:49.360 So this is what we're interested in at the moment. So we can pass in the drink.cost which is the 124 10:49.360 --> 10:52.270 attribute that's associated with the drink object, 125 10:52.750 --> 10:59.110 and that cost is going to be processed by this make_payment method from the money machine. 126 10:59.740 --> 11:05.020 And then finally, it's going to tell us whether if this was successful or not. 127 11:05.410 --> 11:08.200 So let's see what happens when we run this code as it is. 128 11:09.230 --> 11:11.230 Let's say I wanted a latte, 129 11:12.170 --> 11:14.820 notice how it's asking me to insert coins: 130 11:14.840 --> 11:22.340 how many quarters, how many dimes, how many nickels and how many pennies. A the coffee machine, 131 11:22.700 --> 11:28.490 I don't actually need to care about how the money and the coins are processed. 132 11:29.090 --> 11:35.180 All I had to do is call make_payment and it deals with all of this automatically. 133 11:36.170 --> 11:43.430 Finally, it gives me the change and it returns true, telling me that this make_payment was indeed 134 11:43.430 --> 11:44.240 successful. 135 11:45.140 --> 11:52.610 If you actually look inside the money_machine code, then you can see that it has a method called process_ 136 11:52.610 --> 11:56.790 coins, but it's called when make payment is triggered. 137 11:57.290 --> 12:02.960 This class is going to process coins, and then it's going to decide whether if it was successful 138 12:03.170 --> 12:07.820 or not. And if it was successful, it's going to add the cost to the profit, 139 12:08.120 --> 12:13.130 and if not, it's going to tell you that that was not enough money and your money is refunded. 140 12:14.980 --> 12:23.620 Coming back over here, if this is successful, then that means the user has managed to pay and we fulfilled 141 12:23.680 --> 12:27.850 step 3 and 4 just using one method. 142 12:28.960 --> 12:32.440 The final thing we have to do is to actually make the coffee. 143 12:33.160 --> 12:35.830 And that, of course, happens right at the end here. 144 12:36.430 --> 12:42.730 And all we have to do to make the coffee is get hold of the coffee maker object and then call the make_ 145 12:42.730 --> 12:48.220 coffee method and we can pass in the order, which is our drink. 146 12:48.700 --> 12:54.850 Because remember that the make_coffee method expects a menu item as the input parameter. 147 12:55.990 --> 13:03.280 We can actually simplify this code even more by saying, well, if the coffee maker is_resource_sufficient 148 13:04.030 --> 13:11.620 and the money machine was able to take payment, well then we can get the coffee_maker to make coffee. 149 13:12.310 --> 13:14.320 So now let's go ahead and run our code. 150 13:16.530 --> 13:21.930 And let's report to begin with, to see how much resources we have to begin with. 151 13:22.380 --> 13:24.780 And then let's order a coffee. 152 13:26.930 --> 13:30.890 Insert lots of money and we've got our coffee back. 153 13:31.400 --> 13:39.800 So now let's go ahead and order a different coffee, latte, and let's go ahead and insert lots of money. 154 13:40.370 --> 13:42.380 And you can see, here's my latte. 155 13:42.770 --> 13:49.910 But now, if I hit report, you can see that the objects, the coffee maker has been managing our resources 156 13:50.420 --> 13:53.240 and the money_machine has been managing our profit. 157 13:53.960 --> 13:59.900 Now, if I decided to order another latte, then it should actually tell me, sorry, there's not enough 158 13:59.900 --> 14:04.520 water and there's not enough milk. So it can't make me that drink. 159 14:05.150 --> 14:12.650 And we've managed to achieve all of this functionality by writing very few lines of code, and the code 160 14:12.650 --> 14:16.130 itself is actually very, very easy to understand. 161 14:16.370 --> 14:22.840 Even if you came to this completely fresh, you've never seen how each of the methods are implemented, 162 14:22.850 --> 14:24.440 you don't know how the coffee maker works, 163 14:24.710 --> 14:26.240 you don't know how the money machine works, 164 14:26.540 --> 14:29.000 you can see quite easily what it's trying to do. 165 14:29.960 --> 14:35.660 And so if you only have to write this kind of code, then it would make it so much easier to create 166 14:35.660 --> 14:39.440 even more complex functionality in your coffee machine, right? 167 14:40.430 --> 14:43.130 So have a play around with these classes: 168 14:43.580 --> 14:50.270 the coffeeMaker, the moneyMachine, the menu, the menu item, etc. And see what else it is that 169 14:50.270 --> 14:51.590 you can do with this code 170 14:51.860 --> 14:55.880 while not touching any of the blueprints for each of these classes. 171 14:57.200 --> 15:02.660 Now, in the next lesson, I'm going to be showing you how to create your own classes so that you can 172 15:02.660 --> 15:07.880 actually start structuring your code using full object-oriented programming. 173 15:08.390 --> 15:14.420 And we're going to learn about these things like the initialization and how classes are declared and 174 15:14.420 --> 15:16.910 why there's all this self all over the place. 175 15:17.630 --> 15:20.480 That's all yet to come on tomorrow's lessons.