WEBVTT 00:00.480 --> 00:05.710 And let's finish off the rest of this mini project we're doing. 00:06.240 --> 00:13.710 So when you left off we still need to implement the precise context to me and we still have to have 00:13.790 --> 00:19.340 the same contacts so let's do that. 00:19.890 --> 00:25.660 So let's start with the recap resize contacts. 00:26.410 --> 00:28.080 This copy this 00:31.160 --> 00:32.910 Clairette up here. 00:38.290 --> 00:44.760 It's a it's not going to return anything. 00:44.870 --> 00:47.380 Take this reference 00:53.090 --> 00:53.570 so 00:56.010 --> 01:09.160 in it's the new capacitor you're right it's either new capacity for the data it's in wow. 01:09.270 --> 01:12.600 While we're at it let's also declare this on 01:23.030 --> 01:25.330 this churn anything 01:29.260 --> 01:32.020 in this one doesn't need to change. 01:32.130 --> 01:32.980 It's. 01:36.210 --> 01:48.260 K so it's implement these two. 01:49.930 --> 01:53.690 Let's move this up actually. 01:55.430 --> 02:02.240 Here because this is going to do file I own this is also an HD file. 02:02.430 --> 02:02.890 OK. 02:02.970 --> 02:06.300 And we'll save all the files for last. 02:06.300 --> 02:09.510 So let's do the resize now. 02:12.510 --> 02:16.730 So how will resize work. 02:17.220 --> 02:27.710 Basically what we want to do is to essentially we're going to create a brand new array of this new capacity 02:28.460 --> 02:35.850 and we're going to copy all of our current contacts into that new array. 02:36.380 --> 02:44.990 And then we're going to delete the current array and then assign it assigned the contacts divvies array 02:45.110 --> 02:48.130 to be the new the new one that we made. 02:48.480 --> 02:48.940 OK. 02:49.010 --> 03:04.460 So that's going to be something like make you array of size new capacity. 03:04.710 --> 03:08.520 Then we're going to copy all existing 03:11.170 --> 03:18.450 contact it's into the new array right. 03:19.780 --> 03:24.890 And then we're going to delete the 03:27.790 --> 03:36.390 old Ray and then we're going to set up contacts 03:38.340 --> 03:39.250 Eby 03:42.030 --> 03:48.370 winter contacts to be the new Eric 03:53.980 --> 04:02.370 cause you can't just delete the old array right away because we need we still need all those contacts 04:02.390 --> 04:05.360 right now otherwise we lose them all. 04:05.840 --> 04:11.480 So that's why we need to kind of make a new one and then copy all the existing contacts into into that 04:11.480 --> 04:18.590 new one then delete the old one then set the contacts be the new array. 04:18.720 --> 04:19.440 OK. 04:19.820 --> 04:23.480 So let's start with this one is pretty easy. 04:25.090 --> 04:26.520 Contact us 04:29.390 --> 04:32.630 or new contacts. 04:32.640 --> 04:35.470 Winter you 04:38.440 --> 04:44.860 capacity. 04:45.120 --> 04:56.760 Contact just make sure it's in then we need to copy all the existing contacts into this new array. 04:56.780 --> 04:57.030 Right. 04:57.030 --> 05:00.180 Because right now this is empty. 05:00.490 --> 05:08.000 Four times zero is this thing thin contacts divi DOT 05:11.820 --> 05:15.260 number. 05:17.960 --> 05:18.590 Plus 05:21.360 --> 05:21.860 k. 05:21.960 --> 05:28.860 So now we shared essentially just copy it up. 05:28.910 --> 05:31.200 So ster Oppy 05:36.470 --> 05:37.100 copy 05:40.230 --> 05:42.260 of the new contacts are 05:46.830 --> 05:50.000 dot watch first name 06:02.440 --> 06:05.710 that you've seen for the last name 06:14.770 --> 06:22.720 in the new scene for phone number 06:34.390 --> 06:37.940 in it for that. 06:38.070 --> 06:39.870 And then we will. 06:39.870 --> 06:43.710 First we should check to see if it's null pointer because if it's null pointer we don't want to delete 06:43.710 --> 06:44.660 it. 06:44.730 --> 06:47.480 So on tax. 06:50.300 --> 06:51.890 Mixtures not known pointer 06:54.580 --> 06:56.370 in if it's not in real 07:03.610 --> 07:06.060 back in will just set it. 07:06.070 --> 07:09.160 We know set it after all so your 07:23.110 --> 07:23.550 so 07:26.590 --> 07:38.740 and then we will set the pointer contacts the 0.03 should be the new contacts. 07:41.350 --> 07:44.670 Like that and then will also set the new 07:47.310 --> 07:47.880 capacity 07:56.850 --> 07:58.360 like that. 07:59.710 --> 08:03.080 So hopefully this makes sense of what's happening. 08:04.200 --> 08:11.740 So that's really it for resizing. 08:11.800 --> 08:16.300 Now we just need to load the contacts and save the contacts. 08:16.300 --> 08:16.960 OK. 08:17.530 --> 08:23.360 And let's do this by using binary files. 08:23.370 --> 08:27.280 Ok just to make it easy. 08:28.290 --> 08:31.910 So let's start with saving the contacts. 08:32.020 --> 08:36.340 So say oh lifestream file 08:39.510 --> 08:42.110 OK and we'll say out file 08:45.540 --> 08:50.700 open you see. 08:51.020 --> 08:52.840 Well I need the file name. 08:52.850 --> 08:54.290 So it's actually 08:57.030 --> 08:58.650 up here. 08:59.350 --> 09:02.850 So it's still 09:08.350 --> 09:19.680 and what his name it contacts or something been for binary by the way or it doesn't. 09:19.720 --> 09:23.000 That's not a real extension so don't worry about it. 09:25.470 --> 09:33.010 So open contacts name and we're going to open it for a binder 09:38.560 --> 09:42.280 OK and we'll check to see if we opened it. 09:49.950 --> 09:54.480 And if it is then we'll write it to the 09:57.500 --> 09:58.670 rate for that. 09:58.680 --> 10:08.450 And in this case again we still have to write it in in characters essentially. 10:08.490 --> 10:10.530 So one so this is one byte. 10:10.590 --> 10:13.700 So we have to write it in one byte chunks. 10:14.340 --> 10:19.750 So we'll just cast the contract. 10:20.350 --> 10:33.320 You need a pointer contacts to be source essentially setting it to be the first bite of this array. 10:33.870 --> 10:41.280 And then we need to know how many we're writing so how many writing is context to beat the number of 10:41.280 --> 10:45.140 contacts times the size of a contact 10:49.990 --> 10:57.960 so we're reading this many contacts and it's of this so it's so. 10:58.140 --> 11:05.390 And then we'll just close the file. 11:05.780 --> 11:08.970 And that's really it for the save contacts. 11:09.380 --> 11:19.640 And we only have one more to go which is the load contex So 11:22.070 --> 11:24.510 here we need the live stream 11:28.270 --> 11:28.880 final 11:31.280 --> 11:41.570 infile the open rate we're opening for reading or reading only just like we're opening this one for 11:41.570 --> 11:43.180 writing only. 11:45.860 --> 11:46.280 It's 11:52.040 --> 11:56.860 it's for binary. 11:57.340 --> 11:59.520 Would check to see if it's open 12:05.540 --> 12:14.080 and if it is OK we're going to use that same trick we did before you know how big the file. 12:14.090 --> 12:22.460 So if you remember we said in file C and C to the end right. 12:26.060 --> 12:28.970 And we need the like of 12:31.780 --> 12:41.910 file in bytes so infile that tell G Very. 12:41.990 --> 12:44.390 And then we go back to the beginning. 12:44.420 --> 12:44.720 Right. 12:44.730 --> 12:49.890 So in file this sheet 12:58.140 --> 13:06.060 so says go to the end of the file tell me what position the current byte is at which basically just 13:06.060 --> 13:13.500 gives me or current character is that and this just gives me how many bytes are in the file. 13:13.500 --> 13:13.820 Right. 13:13.920 --> 13:20.940 So if it's like 100 it's 100 bytes and then we just go back to the beginning so we can actually do the 13:20.940 --> 13:22.800 proper reading. 13:22.800 --> 13:26.930 So this only gives us how many bytes are in the file. 13:26.940 --> 13:30.920 But this doesn't tell tell us how many contacts we have. 13:30.920 --> 13:31.640 Right. 13:31.650 --> 13:40.610 So if we want to know how many contacts we have we have to say this number of contacts equals the length 13:41.450 --> 13:49.290 of file in bytes over the size of a contact or eight. 13:49.420 --> 13:53.220 So a contact has a certain size right in bytes. 13:53.420 --> 14:00.650 And if we'd divide the length of the file and bytes over that size that will tell us how many contacts 14:00.740 --> 14:04.160 we created initially. 14:06.720 --> 14:10.950 And then here will create the capacity 14:14.050 --> 14:18.970 as being the number of contacts 14:22.180 --> 14:25.900 times two plus 10. 14:26.120 --> 14:32.230 So we just kind of said how many there are based off of how many we wrote before. 14:32.410 --> 14:37.710 And then we just need to set all our contacts. 14:38.170 --> 14:48.000 Well first we need to actually set set pointer or actually knew the memory right. 14:48.270 --> 14:54.410 What do your contacts because when we load it when we only load it once at the very beginning. 14:54.720 --> 14:57.720 So when we load it this is set to no pointer. 14:57.750 --> 15:02.520 So it's not actually pointing at any memory at need point to that a memory 15:06.370 --> 15:07.850 city. 15:08.290 --> 15:17.610 This and then we say contacts he'd got a number of contacts we know how many that is 15:20.990 --> 15:23.410 in a capacity 15:31.330 --> 15:35.690 capacity like that. 15:36.070 --> 15:44.850 Now our context is it finally initialized now need to actually read it or read it. 15:44.890 --> 15:45.860 Sorry. 15:46.160 --> 15:51.350 Read should look exactly like the right for 16:03.270 --> 16:06.510 and we read how many bytes are in the fight right. 16:15.430 --> 16:17.330 Then just close the file 16:21.780 --> 16:25.880 and return true that it actually read everything. 16:29.060 --> 16:33.140 So that's it for that. 16:36.150 --> 16:37.490 So are we done. 16:40.060 --> 16:43.370 Oh we load the contacts right. 16:44.330 --> 16:46.820 And all that. 16:46.850 --> 16:49.430 So that's OK. 16:49.520 --> 16:53.420 And the last thing we should do is say if 16:56.430 --> 17:02.430 if we have loaded the contact or if we haven't learned the contacts we should kind of output that we 17:02.430 --> 17:02.790 didn't 17:05.660 --> 17:07.230 didn't. 17:07.700 --> 17:11.430 Error eating file 17:16.710 --> 17:18.330 the file name 17:24.870 --> 17:25.590 it's 17:28.270 --> 17:36.250 Annibale kind of return zero here because if we can't write read the file then we can't do anything 17:36.370 --> 17:37.400 right. 17:37.450 --> 17:40.190 So let's run this. 17:40.280 --> 17:40.770 You. 17:41.510 --> 17:49.230 It's so everything foul contacts up in. 17:49.350 --> 17:50.150 OK. 17:50.380 --> 17:53.840 So why why do you think that is. 17:53.990 --> 17:54.830 Right. 17:54.950 --> 18:00.070 So the reason is because the file doesn't exist. 18:00.370 --> 18:07.390 And we said before that if you actually write to the file it'll create the file but we'd never have 18:07.390 --> 18:08.520 written to the file. 18:08.530 --> 18:12.610 So how do we create it. 18:13.600 --> 18:16.330 Here's a little trick that we can do. 18:16.360 --> 18:18.610 So I'm going to write one more function 18:21.320 --> 18:33.430 in void and say create contact us file and copy this 18:36.970 --> 18:41.880 and we're going to paste it here. 18:46.540 --> 19:00.970 And we're going to try to see if we can open the file OK and if we can't open the file we will actually 19:01.000 --> 19:02.500 create the file. 19:04.510 --> 19:18.050 And open tax file name stream Harry. 19:18.120 --> 19:28.060 If not you can file is open so we couldn't open the file. 19:28.080 --> 19:30.260 That probably means we haven't actually created it. 19:30.300 --> 19:31.970 So we'll say off stream 19:36.880 --> 19:37.760 file. 19:39.780 --> 19:43.290 And we'll say oh file it open 19:45.860 --> 19:46.780 again. 19:49.090 --> 19:49.670 Street 19:52.100 --> 20:05.670 Nery write and I would like to effectively make an empty five day and how you do that is this is out 20:05.720 --> 20:12.430 file and insertion operator and we'll say flush and then close it 20:16.630 --> 20:18.490 so flesh will actually 20:21.520 --> 20:28.210 essentially write out nothing but this will still create the file. 20:28.860 --> 20:36.650 So that's kind of a nice little trick you can do if you just want to flush the entire file. 20:36.650 --> 20:41.970 So it basically just makes a 0 byte file is this. 20:42.300 --> 20:53.310 So it opens it or does kind of flush meaning a just please just create it right and then close and then 20:53.340 --> 20:57.380 otherwise otherwise you could open it. 20:57.380 --> 20:58.570 So you should close it 21:03.330 --> 21:07.730 and up here we will actually create its 21:12.120 --> 21:15.020 if it's not created already. 21:15.630 --> 21:20.410 And there's one thing that we should do after the loop is done. 21:25.150 --> 21:27.700 Which is save the contacts 21:30.100 --> 21:32.200 so if we quit we should just save them all 21:35.520 --> 21:41.670 and we should also delete the memory right. 21:41.730 --> 21:42.420 We haven't done that 22:09.170 --> 22:09.640 today. 22:09.650 --> 22:11.680 This is just good practice to do. 22:13.020 --> 22:18.140 So no I think that's kind of it. 22:18.230 --> 22:21.730 It's be missed anything right. 22:24.160 --> 22:27.510 So let's read this and see what happens. 22:30.360 --> 22:34.320 So notice we actually got to the main screen. 22:34.590 --> 22:39.210 So it actually was able to load even though it probably has nothing. 22:39.360 --> 22:40.230 OK. 22:40.230 --> 22:44.580 So what happens if we display nothing happens. 22:44.600 --> 22:48.200 Let's try to add something. 22:48.280 --> 23:01.150 So please enter the first name Fred last name and and please enter a number 23:03.750 --> 23:06.840 saved and see if that actually worked. 23:08.300 --> 23:14.540 So Fred Flintstone then has the very first phone number in existence right which makes sense. 23:15.120 --> 23:17.070 OK let's add something else 23:27.460 --> 23:28.190 OK. 23:28.270 --> 23:29.850 So there you go. 23:30.950 --> 23:38.990 So we have a list of contacts that we can add to which 23:44.390 --> 23:48.180 so flee all of that made sense. 23:48.170 --> 23:54.290 And we found this kind of interesting this is really just a good review. 23:54.380 --> 24:05.660 And it is also to illustrate to I guess more of the advanced students how to not always have to do a 24:05.660 --> 24:06.900 top down design. 24:06.980 --> 24:07.210 Right. 24:07.200 --> 24:11.120 We can kind of do this piecemeal as it makes sense. 24:11.130 --> 24:11.910 OK. 24:12.290 --> 24:20.830 Which is which is usually the more common method that programmers will use sort of. 24:21.050 --> 24:28.160 Right the usage code even though you don't have the code at all and then make sure that makes sense 24:28.220 --> 24:37.730 and it solves the problem and then actually go back and implement everything that that you had you declared 24:37.730 --> 24:39.050 before. 24:40.670 --> 24:46.700 So that's kind of a more natural way and that's usually the more it's usually the way I approach problems. 24:46.700 --> 24:56.510 Now I rarely do a top down design especially for really big projects you usually want to break a small 24:56.510 --> 25:03.760 piece of it right down and just implement that and then test it and see if it's working. 25:03.950 --> 25:05.860 And then kind of add on to it. 25:06.100 --> 25:13.650 And and that's really b approach will take for the very final project in this course. 25:13.880 --> 25:16.740 So I will see you in the next section.