WEBVTT 00:00.760 --> 00:09.820 So instead doing some regular practice problems for this section what we do sort of a mini project kind 00:09.820 --> 00:18.140 of review thing we've learned up to this point and including the file IO that we just learned. 00:19.910 --> 00:29.320 So let's take a look at the problem pretty program that will keep a list of contacts the contact will 00:29.320 --> 00:35.580 have a name of worsening last name and a phone number with no dashes. 00:36.070 --> 00:40.700 The program will read in all the saved contacts at the start of the program. 00:41.800 --> 00:50.390 User will be able to either look at all the contacts or add new contacts or quit. 00:50.560 --> 00:59.250 And once the contact is added it should be say the name should be no more than 256 characters. 00:59.320 --> 01:04.090 So let's start breaking down the problem. 01:04.660 --> 01:06.780 Are these the data of the problem. 01:07.060 --> 01:15.010 So I notice that we need some kind of contact and it will have a name. 01:15.680 --> 01:24.790 Well first name a last name and a phone numbers so that tells me that we should have a struct or a struct 01:24.880 --> 01:27.110 and call it contact. 01:30.610 --> 01:36.550 And it has a first name something that make a E-Strings a first name 01:40.840 --> 01:43.740 and you'll have Max doing 56 characters. 01:43.750 --> 01:51.440 In fact you need such an same size 01:54.410 --> 01:58.630 yes it's characters. 01:59.060 --> 01:59.560 Here 02:05.630 --> 02:08.130 so and do that for the last name 02:14.840 --> 02:19.590 is and says we have a phone number with no dashes. 02:19.590 --> 02:23.780 It just means integer number 02:26.710 --> 02:30.170 so we have an object called contact. 02:30.400 --> 02:33.160 And but we need a list of contacts. 02:33.220 --> 02:33.900 OK. 02:34.400 --> 02:41.370 And do something kind of interesting here since we need so I guess an array. 02:41.410 --> 02:48.340 That's the only thing we know right now that has that can store many values right now actually going 02:48.340 --> 02:51.700 to make a new struct 02:54.540 --> 02:58.090 called contact DB. 02:59.140 --> 03:00.150 OK. 03:00.510 --> 03:13.290 And this contact D-B which stands for database will have a pointer to contacts. 03:13.300 --> 03:28.350 Now be kind of the array it all contacts like so and we need to know how many contacts we have. 03:28.350 --> 03:38.880 So number of contacts and one of sweet thing it says it didn't say there's a limit to how many contacts 03:38.970 --> 03:39.950 we can have. 03:39.950 --> 03:40.510 Right. 03:40.770 --> 03:44.680 So we'll just kind of have to assume that there is no limit. 03:45.060 --> 03:56.490 And so to do this we're going to have a capacity of our contact array. 03:56.760 --> 04:04.140 So the contact array will have a number of contacts in how many this array was created for. 04:04.200 --> 04:14.100 So if we create say a thousand capacity would be a thousand even if we only had a 10 actual contacts. 04:14.550 --> 04:19.380 And this is actually the type that we're going to use in order to 04:21.950 --> 04:24.290 hold all our contacts. 04:25.890 --> 04:29.750 So that's really it for the data. 04:29.790 --> 04:31.840 Essentially. 04:32.240 --> 04:36.690 So let's start I guess breaking down the problem. 04:37.640 --> 04:48.000 And I kind of want to we'll kind of do this without really doing a real top down design. 04:48.230 --> 04:53.500 Okay but you'll see kind of how we go about it. 04:53.720 --> 04:58.240 It'll still sort of look like a top line but we'll actually write the code. 04:58.610 --> 05:01.700 So essentially what this is saying is 05:04.780 --> 05:13.210 so user will be able to either look at all their contacts or add new contacts they or quit the app. 05:13.330 --> 05:16.270 And so these are the things that the user is able to do. 05:17.280 --> 05:25.380 K so there's three options that they're able to do so that's actually 05:28.540 --> 05:32.750 right out kind of the baseline of everything. 05:32.770 --> 05:38.140 So let's say we need the option that they can do 05:42.110 --> 05:45.310 and we'll go through 05:48.190 --> 05:50.230 and while the option 05:53.290 --> 05:57.290 is not it's quit of quit odysseys. 05:57.310 --> 06:06.540 Q And we'll kind of do the option or get the option from these areas. 06:10.660 --> 06:21.140 User and we will kind of execute this option game or do the option 06:24.410 --> 06:26.150 again we don't have implementations for this. 06:26.150 --> 06:30.280 We're just sort of designing how it's going to work. 06:31.760 --> 06:34.220 Using the option. 06:36.200 --> 06:40.320 And of course we'll probably need our contactee. 06:40.350 --> 06:41.050 So 06:43.710 --> 06:46.110 this is called contact. 06:46.110 --> 06:47.230 It's the 06:55.130 --> 06:55.610 X 06:58.210 --> 07:04.450 the like so and initially it will be empty. 07:05.080 --> 07:06.070 X TV. 07:06.090 --> 07:15.490 So Dot we don't have any right because we haven't read Minya and 07:18.500 --> 07:23.340 you set the size number contact's zero. 07:25.210 --> 07:27.320 And capacity currently zero. 07:27.430 --> 07:28.220 Right. 07:28.270 --> 07:34.960 The very start of her and we don't have anything so everything's kind of just default. 07:37.000 --> 07:44.600 So it says at the start of the program it will read in the list of contacts. 07:45.950 --> 07:53.340 So we'll need some way of loading all of our current contacts if it exists. 07:53.340 --> 08:04.150 So at this start we'll say lude on tax 08:06.520 --> 08:07.840 contacts 08:10.510 --> 08:15.770 the OK so will need to load it somehow. 08:15.820 --> 08:16.270 Right. 08:20.700 --> 08:22.390 Ask Nizer. 08:22.660 --> 08:29.260 OK so we load the contacts will get the option from the user and then we'll just keep the option. 08:29.260 --> 08:36.580 But what I guess will need to also pass in the contacts range because what if they want to add something 08:37.680 --> 08:40.380 and will need context. 08:41.030 --> 08:45.310 So this is another way you can sort of design your program. 08:45.320 --> 08:50.810 It doesn't always have to be the top down design method that we've been use and you know that's kind 08:50.810 --> 08:53.890 of what we're doing right now anyway. 08:54.170 --> 08:59.780 It just means that we don't have to always kind of write out all the pseudo code first and then then 08:59.780 --> 09:06.860 code after which is kind of going against what I told you before but that was really to help you solve 09:06.860 --> 09:07.760 the problem. 09:07.850 --> 09:10.140 And we're still solving the problem. 09:10.160 --> 09:16.820 So right now we're just sort of kind of writing B. 09:17.990 --> 09:25.220 The main function and that'll kind of guide us to you what everything what what we need to do for to 09:25.220 --> 09:26.560 actually solve the problem. 09:26.730 --> 09:33.440 OK so now we have these kind of functions and are not intimate at all really yet. 09:33.440 --> 09:34.020 Right. 09:34.160 --> 09:36.290 That's all this is all we've done. 09:36.320 --> 09:37.230 Not too much yet. 09:38.130 --> 09:46.030 So you need to get the option from the user and execute the option and load context right. 09:47.560 --> 09:50.770 So we'll need those functions. 09:50.810 --> 09:54.410 So you just declare them so. 09:54.610 --> 10:00.220 Option from user will be character or return of character. 10:00.220 --> 10:03.280 This will just be our get character function. 10:05.410 --> 10:05.900 There 10:10.130 --> 10:13.720 they execute option or turn nothing. 10:13.730 --> 10:32.700 And it will take us CH and it will take the option and the contacts Stevy probably by reference ranks 10:33.210 --> 10:33.990 could change 10:41.500 --> 10:50.360 so and we also need load contex. 10:50.810 --> 10:57.110 We're actually going to make it Boullion and going to keep building because what if the file doesn't 10:57.110 --> 10:58.570 exist yet. 10:59.450 --> 11:00.200 So 11:03.360 --> 11:18.510 X is also the right reference. 11:18.570 --> 11:23.750 And let's kind of just to some of the it's 11:31.910 --> 11:36.050 not going to rate everything at this kind of rates. 11:36.060 --> 11:39.380 And some of the simple ones. 11:39.600 --> 11:55.410 So this option from user We just want to call and everready included the huge hills to peer mood tunes 11:55.680 --> 11:57.240 h Gach 11:59.970 --> 12:05.500 and you should actually get it OK. 12:05.580 --> 12:09.200 So we're going to have three options. 12:09.210 --> 12:15.660 So cons are options for the proper input. 12:16.090 --> 12:23.290 Say d is for display everything a is for adding and for. 12:26.440 --> 12:27.830 A return. 12:29.140 --> 12:30.480 Get character 12:34.020 --> 12:44.500 the prompt will be please choose option. 12:44.840 --> 12:50.930 New lines in here and I'll just say I like D for display. 12:54.100 --> 12:55.090 Contact's 12:57.350 --> 13:14.700 in a we're adding contacts and Hugh. 13:14.870 --> 13:18.840 A What is your choice. 13:22.180 --> 13:22.760 I like that. 13:22.920 --> 13:30.070 So I remember that slash and is for a new lines like the Entergy essentially. 13:30.130 --> 13:35.130 So the next thing we need is the error strings right. 13:36.440 --> 13:42.280 Such and such for string 13:46.220 --> 13:49.880 you're. 13:50.570 --> 13:54.010 Again so 14:01.910 --> 14:12.330 that in and of course all the options three of them and we'll say C C lowercase 14:15.010 --> 14:20.430 and it's lowercase because you use lowercase Q here for quit. 14:21.680 --> 14:23.080 It's Y. 14:23.310 --> 14:26.180 So that's kind of it for this. 14:26.180 --> 14:29.330 So let's just run this and see 14:33.310 --> 14:40.330 that. 14:40.330 --> 14:42.760 So what is your choice. 14:42.760 --> 14:48.160 A Nothing happens D nothing happens. 14:48.160 --> 14:55.970 Q It's gay that's for that and let's rate execute option. 14:58.090 --> 15:02.300 So here we'll do a switch on the options 15:06.460 --> 15:16.230 have a case for adding a and for this will say well need new function. 15:16.240 --> 15:18.160 I'll just add option 15:21.650 --> 15:22.110 and 15:26.130 --> 15:26.670 Imbert 15:30.150 --> 15:41.010 and don't need another one for displaying the same display and contacts 15:46.490 --> 15:54.930 so notice how we're kind of doing the stuff this now. 15:55.160 --> 16:00.180 So we're kind of doing the design of this kind of piecemeal right. 16:00.280 --> 16:04.860 So we just kind of said oh I'll probably need something like this for I get the option for Muser and 16:04.860 --> 16:10.390 then I have to actually do the option from the user right and then we'll do that while he doesn't want 16:10.390 --> 16:11.340 to quit. 16:11.410 --> 16:11.980 Right. 16:12.100 --> 16:18.640 So that's how we kind of came up with this main loop and same with like this all we need to somehow 16:18.640 --> 16:22.600 read it into the actual context. 16:22.970 --> 16:25.690 Right no we haven't done that yet. 16:25.720 --> 16:33.340 And similarly here next cute option we need some way of adding a contact and it's a way of displaying 16:34.000 --> 16:35.270 all the contacts. 16:35.270 --> 16:36.090 Right. 16:36.340 --> 16:41.220 So we're just kind of doing this piecemeal and what we think makes sense. 16:41.710 --> 16:49.150 So we're still sort of doing this top down design we're just not writing at all in pseudo code for us 16:49.180 --> 16:53.230 we're just kind of writing code as we kind of think of it. 16:55.520 --> 16:59.580 So we need to add option and display option. 16:59.630 --> 17:07.040 So it's this or read option 17:09.820 --> 17:16.200 and it's going to take the context D-B by reference. 17:16.730 --> 17:18.640 Change the contacts there. 17:20.790 --> 17:22.590 And we need display. 17:22.740 --> 17:30.230 It's display option. 17:30.380 --> 17:33.590 This will be by conc because we don't have to change it. 17:43.580 --> 17:44.690 Copy this 17:48.620 --> 17:49.980 piece it down here. 17:55.050 --> 17:55.750 OK. 17:56.290 --> 18:03.160 So let's kind of implement the display option should be quite simple. 18:03.820 --> 18:10.360 So we just loop through all of our contacts and then display contact. 18:10.500 --> 18:17.500 So 4 0 is less than an hour. 18:17.810 --> 18:23.480 It's the number of contacts it's right. 18:26.990 --> 18:31.400 And all we do is just put everything in the name 18:33.680 --> 18:34.640 is 18:37.330 --> 18:42.020 going to tax the rich winter. 18:42.530 --> 18:46.820 First rate. 18:47.030 --> 18:53.460 And that's because this kind of this is called the indexing operator. 18:53.510 --> 18:54.730 Right. 18:54.950 --> 18:58.190 That we've been using for arrays and this actually will dereferences. 18:58.190 --> 19:01.090 So that's why we don't need a star or a star. 19:01.100 --> 19:04.910 But this thing is Arrow right. 19:05.100 --> 19:06.800 You reference it it's say Dot 19:11.830 --> 19:13.540 and we'll do that for the last few 19:27.860 --> 19:28.550 mean and 19:31.760 --> 19:34.260 then we'll put the phone numbers on 19:41.400 --> 19:42.040 there 19:57.160 --> 20:04.880 and we'll put two initials here because we want a space between each entry. 20:05.910 --> 20:09.090 And that's really it for display option really. 20:09.090 --> 20:12.560 So again we're just sort of doing this all piecemeal right. 20:12.690 --> 20:18.370 Or just kind of taking a little piece of work and then reading that code the way we think it should 20:18.390 --> 20:22.940 work and then we're moving on to the next part right. 20:24.000 --> 20:29.420 So add option it's go with this. 20:29.610 --> 20:35.160 This will be a little bit more complicated I think. 20:35.230 --> 20:41.570 So like I said before in the program it never said that we could have. 20:41.710 --> 20:47.220 There's no upper limit to how many contacts we can have. 20:47.410 --> 20:48.030 OK. 20:49.620 --> 20:59.490 So that means that we need to grow our contacts array any time that we're at the maximum. 21:00.730 --> 21:04.960 So here now let's say if 21:07.570 --> 21:23.500 the contacts D-B dot the number of contacts is somehow equal to the capacity then we somehow need to 21:23.530 --> 21:30.460 resize this whole this whole contacts D.B right we need to grow it to be bigger. 21:30.490 --> 21:33.570 So we can add more contacts. 21:34.060 --> 21:40.730 So say resign as contact us Eby. 21:40.980 --> 21:49.280 And so we're just kind of kind of eyeballing this right we're kind of just like going off the cuff a 21:49.280 --> 21:50.260 little bit. 21:50.260 --> 21:56.540 We're just saying Oh like we see a problem and then we just kind of I'm just writing a function that 21:56.690 --> 22:04.880 doesn't exist yet and we're saying OK it's going to it's just going to resize this thing somehow we 22:04.880 --> 22:06.010 don't know yet. 22:06.090 --> 22:06.500 Right. 22:06.860 --> 22:08.750 So how much should we need. 22:08.810 --> 22:12.430 Well need the context to me obviously that's what resizing. 22:12.470 --> 22:15.280 So how much should we resize it by. 22:15.300 --> 22:18.710 We could just add one right too. 22:18.770 --> 22:22.790 So we just make capacity one more right. 22:22.970 --> 22:30.670 But instead of that because we don't want to resize it all the time are actually going to say contacts. 22:30.710 --> 22:34.540 TB dot capacity. 22:34.820 --> 22:44.300 And when you say times 2 and then plus 10 so we'll multiply whatever the capacity is times 2 and then 22:44.300 --> 22:46.570 just add 10 more. 22:46.760 --> 22:47.330 Okay. 22:47.630 --> 22:52.660 And I'm doing this because what if the capacity with zero. 22:52.900 --> 22:53.860 Right. 22:54.170 --> 22:56.960 Which is which it is at the very start. 22:57.030 --> 22:57.460 Right. 22:58.780 --> 23:07.100 And what if it was zero then contacts D.B capacity which is zero times to zero. 23:07.300 --> 23:10.610 So if I didn't have this plus 10 they would still amount to zero. 23:10.620 --> 23:13.220 So that's why I'm kind of just adding a few more. 23:13.340 --> 23:18.660 OK so what does resize. 23:18.850 --> 23:28.360 And then once it's resize and everything's good then we will actually get all the input. 23:28.360 --> 23:40.250 So the next thing we need to do is actually get the first name and last name so don't have a way in 23:40.270 --> 23:48.510 you to actually get a string although we've done that in hangman before. 23:48.650 --> 23:50.180 Right. 23:50.270 --> 23:59.780 So what I've done you tildes is I've actually added a method called Get string and I I took this directly 23:59.780 --> 24:09.170 from hangman and I use sort of the same signature as get character with like the valid input or not 24:09.170 --> 24:16.820 that out and put it like the scared character with the prompt in the air and actually just feel this 24:16.820 --> 24:17.950 string. 24:18.080 --> 24:23.090 And with some maximum. 24:23.180 --> 24:32.910 So if you want to take a look at how I implemented this it you shouldn't be surprised what's happening. 24:32.910 --> 24:33.180 Right. 24:33.200 --> 24:41.730 So we get the string string which is named the function a failure we have a length. 24:41.750 --> 24:52.740 Again I just stole this basically exactly from hangman and the one thing I added was this line. 24:52.770 --> 24:57.560 So by the way if you want to copy this down just pause the video and then copy the whole thing. 24:57.660 --> 25:08.290 OK so the one thing I did add that that's new is this line right here which will kind of get the whitespace. 25:08.290 --> 25:15.120 This is actually a special thing that kind of comes with the scene in I'll stream and this will get 25:15.150 --> 25:20.060 all the white space before we actually get the string. 25:20.580 --> 25:22.960 It's kind of weird why we need to do this. 25:23.340 --> 25:33.140 But sometimes I guess the input stream really doesn't clear properly once we get once we call this get 25:33.400 --> 25:35.650 function k. 25:35.790 --> 25:37.790 So that's why we kind of need it here. 25:37.800 --> 25:44.970 So just remember to put this whitespace see in whitespace here. 25:45.200 --> 25:50.020 Otherwise I've also added this doesn't matter too much I don't think. 25:50.030 --> 25:53.460 But I bet it doesn't matter. 25:54.410 --> 25:59.720 And everything else should be the same in all it does is turn the length of the string that you got 26:00.100 --> 26:02.060 and that's it. 26:02.060 --> 26:06.830 So this is directly from Hank except for this part. 26:07.340 --> 26:09.290 So let's go back. 26:09.290 --> 26:12.920 So here I wanted to say get string 26:15.380 --> 26:21.190 and or say please enter first name 26:24.680 --> 26:28.340 and input it's it's 26:31.050 --> 26:32.280 air string 26:34.590 --> 26:44.270 Turks TV your contacts so are actually going to change this array directly. 26:45.730 --> 26:57.280 And this should be contacts D-B DOT number of contacts so put it in the next available slot is what 26:57.280 --> 26:58.470 this is saying. 26:58.540 --> 26:59.220 Right. 26:59.350 --> 27:08.380 Because if even if we had zero as long as we had some as long as we actually had a positive capacity 27:09.150 --> 27:14.210 I would just add it to the next available slot. 27:14.290 --> 27:16.490 And even if there's a zero this would work. 27:17.410 --> 27:26.420 So first name that's the string and then Max Nemes size as well. 27:27.690 --> 27:28.310 OK. 27:28.480 --> 27:31.450 And again minus one because we're not here. 27:31.960 --> 27:45.810 This puts the knot here and there it was a string these enter the last name. 27:47.660 --> 27:50.370 As your string 27:54.500 --> 27:55.130 xt. 27:55.170 --> 27:59.300 The pointer X 28:06.750 --> 28:09.020 contacts and last 28:21.280 --> 28:25.100 and then we'll just say see each 28:29.590 --> 28:30.490 actually will say 28:33.160 --> 28:36.220 get integer. 28:37.090 --> 28:43.780 So we'll just see an integer here please. 28:46.110 --> 28:47.240 Phone number 28:50.050 --> 28:52.230 is in contact. 28:52.540 --> 28:54.890 It's. 29:05.430 --> 29:11.710 Number of contacts phone number OK. 29:11.770 --> 29:23.050 So that will put the whatever the user input into our into the next available phone numbers. 29:23.790 --> 29:29.570 And then we'll just add one to the number of contacts. 29:29.770 --> 29:31.390 It's the 29:34.400 --> 29:36.860 kinda plus. 29:36.970 --> 29:48.020 And then we'll save contacts and again we do not have this function right. 29:49.750 --> 29:57.220 But but we know we need to save here because in the problem once the contact is added it should be saved. 29:57.380 --> 29:58.200 OK. 29:58.630 --> 30:00.540 So again I'm just I know I'm not doing it. 30:00.540 --> 30:02.470 Top down design for this. 30:02.470 --> 30:09.660 I'm just kind of going off the cuff and just writing the code that I think we will need right. 30:09.710 --> 30:11.830 You know it's just. 30:11.900 --> 30:18.350 I'll just say to the user say. 30:18.910 --> 30:22.050 So I want to call it quits for this lecture. 30:22.060 --> 30:28.780 But in the next lecture we will actually implement the resize all the contacts and we'll implement the 30:28.780 --> 30:33.340 saved contacts and load decks. 30:33.700 --> 30:35.730 So I'll see you in the next lecture.