1 00:00:02,800 --> 00:00:03,670 Hello everyone. 2 00:00:03,670 --> 00:00:09,220 Welcome to this new session and this session we will learn a few more important concepts of Forbes. 3 00:00:09,220 --> 00:00:14,470 If you'll notice in the last session we never used a student name anywhere student name is an important 4 00:00:14,470 --> 00:00:16,470 property that should be included. 5 00:00:16,540 --> 00:00:20,740 So we should have to rename property but we do not include it anywhere. 6 00:00:21,220 --> 00:00:22,330 Why we not included. 7 00:00:22,330 --> 00:00:24,130 Because there is a reason behind it. 8 00:00:24,520 --> 00:00:27,430 So now let's see how we will work on name. 9 00:00:27,430 --> 00:00:28,020 Okay. 10 00:00:28,030 --> 00:00:36,880 So let us create a class a student so let's create a class student. 11 00:00:36,900 --> 00:00:42,090 Now this time I will have two private properties a general number so each will be integer 12 00:00:46,430 --> 00:00:48,820 age will be integer and is a private property. 13 00:00:48,830 --> 00:00:50,690 Now the name will be a string. 14 00:00:50,810 --> 00:00:57,220 So for storing this string we will use a connectivity took our name and letter to the sizes entered. 15 00:00:57,360 --> 00:00:58,160 Okay. 16 00:00:58,460 --> 00:01:00,840 So we should not do this. 17 00:01:00,910 --> 00:01:01,440 Why. 18 00:01:01,490 --> 00:01:03,920 Because now we have started dynamic allocation. 19 00:01:03,920 --> 00:01:06,450 So now we know how to create data dynamically. 20 00:01:06,540 --> 00:01:12,890 So we should not create that is strategically so creating that dynamically index is very simple CAST 21 00:01:12,900 --> 00:01:17,660 OUR NAME IS NEW. 22 00:01:17,860 --> 00:01:18,730 Hundred. 23 00:01:18,820 --> 00:01:19,560 Okay. 24 00:01:19,840 --> 00:01:25,250 So the problem here is there is a problem here and the problem here is that we do not know the size 25 00:01:25,250 --> 00:01:26,230 of the student name. 26 00:01:26,380 --> 00:01:29,150 If it is more than handed then we will be bribed. 27 00:01:29,320 --> 00:01:33,060 If it is less than a hundred then a lot of memory will be wasted. 28 00:01:33,070 --> 00:01:33,600 Okay. 29 00:01:33,700 --> 00:01:37,690 So according to the requirement we will decide the size of the student name. 30 00:01:37,690 --> 00:01:40,180 So for now let's make it a character pointer. 31 00:01:40,900 --> 00:01:41,140 Okay. 32 00:01:41,140 --> 00:01:44,170 So let's make it a character pointer only. 33 00:01:44,370 --> 00:01:48,400 And according to the requirement we will allocate sites. 34 00:01:48,660 --> 00:01:57,450 So now let's create a constructor so the constructor will take two inputs each and lumber. 35 00:01:57,490 --> 00:02:00,140 We are constructing a betterment based constructor. 36 00:02:00,400 --> 00:02:05,740 So int h. 37 00:02:05,920 --> 00:02:10,350 And secondly B name name. 38 00:02:10,880 --> 00:02:11,160 Okay. 39 00:02:11,190 --> 00:02:19,190 So this arrow h we have to use this here because we have to differentiate between the barometer and 40 00:02:19,190 --> 00:02:21,680 the proper barometer and the property agent. 41 00:02:21,680 --> 00:02:30,820 So this shadow reaches age and similarly this add on name is name. 42 00:02:30,820 --> 00:02:38,620 Okay so what constructor is ready now let us create our display function so that we can print so display 43 00:02:41,440 --> 00:02:43,610 so display function. 44 00:02:43,610 --> 00:02:46,940 Let us first bring the value of Nim. 45 00:02:47,060 --> 00:02:49,040 First we had printing the name of the student. 46 00:02:49,100 --> 00:02:56,990 And then we will print the age of the student Okay so now let us create objects 47 00:02:59,920 --> 00:03:01,100 so a student S1. 48 00:03:01,510 --> 00:03:03,580 So is this treatment right or wrong. 49 00:03:03,580 --> 00:03:04,400 So this is wrong. 50 00:03:04,400 --> 00:03:04,980 Why. 51 00:03:04,990 --> 00:03:11,680 Because as soon as we clear the better based constructor then build constructor in both default constructor 52 00:03:11,800 --> 00:03:14,090 is not visible to us anymore. 53 00:03:14,140 --> 00:03:20,140 So this line what it will do it we tried to call inbuilt default constructor and that constructor is 54 00:03:20,140 --> 00:03:23,000 not visible so this line will throw at it. 55 00:03:23,010 --> 00:03:23,510 Okay. 56 00:03:23,620 --> 00:03:25,280 So what we have to do. 57 00:03:25,360 --> 00:03:25,620 Okay. 58 00:03:25,630 --> 00:03:30,950 So first let us create a name a String name. 59 00:03:31,060 --> 00:03:40,990 So can name let's say the name is let's the name is ABC and now let us create a student. 60 00:03:41,020 --> 00:03:50,370 So student is when we have to call parameters constructor let's say that age is 20 and the name is name. 61 00:03:50,390 --> 00:03:50,900 Okay. 62 00:03:51,020 --> 00:03:53,220 So now let us call display function. 63 00:03:53,240 --> 00:03:54,800 So S1 dart display 64 00:03:59,200 --> 00:04:02,310 Okay now that does create. 65 00:04:02,870 --> 00:04:11,260 Okay so now let us change the value of names so let us make the name ABC. 66 00:04:11,270 --> 00:04:14,090 So now the name is ABC. 67 00:04:14,180 --> 00:04:16,400 Now we will create the object. 68 00:04:16,790 --> 00:04:20,390 So student let's name it as two. 69 00:04:20,540 --> 00:04:25,780 So that ages party and the name is name. 70 00:04:25,820 --> 00:04:26,610 Okay. 71 00:04:26,720 --> 00:04:29,420 So now let us call display function 72 00:04:34,990 --> 00:04:35,680 okay. 73 00:04:35,990 --> 00:04:40,350 So if you will run this file what will be our output. 74 00:04:40,460 --> 00:04:41,060 So let's see 75 00:04:46,930 --> 00:04:55,120 so for student S1 name is ABC and ages 20 for students to name is ABC and the ages 30. 76 00:04:55,170 --> 00:04:55,610 Okay. 77 00:04:55,720 --> 00:04:58,060 So this was our expected output. 78 00:04:58,060 --> 00:05:00,200 So there's is nothing new here. 79 00:05:00,280 --> 00:05:06,940 Now what if after printing as to what if after printing as true I am again printing the value of S1. 80 00:05:06,940 --> 00:05:11,800 So what will happen find out dart display function. 81 00:05:11,850 --> 00:05:15,280 Output should be ABC and 20. 82 00:05:15,280 --> 00:05:19,920 Now let's see what do we output. 83 00:05:20,070 --> 00:05:21,990 See there is something wrong. 84 00:05:22,030 --> 00:05:24,680 The output should be the name should be ABC. 85 00:05:25,150 --> 00:05:29,360 But the output is coming out to be ABC okay. 86 00:05:29,380 --> 00:05:30,630 So why is it so. 87 00:05:30,680 --> 00:05:35,220 Let us try to understand what is going good let us analyse what we have done. 88 00:05:42,610 --> 00:05:42,860 Okay. 89 00:05:42,870 --> 00:05:45,010 So what is the effect of this line. 90 00:05:45,060 --> 00:05:45,900 What it will do. 91 00:05:45,900 --> 00:05:55,010 It will create 80 ABC days and then and let's say that those of the 0 10 Nexus 7 ended okay. 92 00:05:55,090 --> 00:06:05,700 So at this line will happen as friend art student name is 20 and it's already ages 20 and name will 93 00:06:05,700 --> 00:06:06,500 be 700. 94 00:06:06,540 --> 00:06:12,110 We all know how good it bad is our past in fact how it is passed we will pass the test of those Littleton 95 00:06:12,160 --> 00:06:16,460 six so seven and I will go from here and that this line what will happen. 96 00:06:16,620 --> 00:06:22,840 So age is 20 and name is 700. 97 00:06:22,910 --> 00:06:25,310 Okay so this is the scenario ahead. 98 00:06:25,560 --> 00:06:27,330 Now what will S1 contain. 99 00:06:27,390 --> 00:06:37,380 So for the S1 age will become 20 and the name which is a character pointer it stores 700 okay too. 100 00:06:37,410 --> 00:06:38,410 This is the scenario. 101 00:06:38,430 --> 00:06:45,240 S1 so basically what is happening here is so the name is pointing towards this name. 102 00:06:45,260 --> 00:06:51,830 Okay so the name of S1 the character pointer is pointing towards this name. 103 00:06:51,900 --> 00:06:55,420 Okay now add this line as our display. 104 00:06:55,500 --> 00:06:56,610 What it will do. 105 00:06:56,610 --> 00:06:59,310 It will print the name and age. 106 00:06:59,310 --> 00:07:00,960 So for name it what it will do. 107 00:07:00,960 --> 00:07:02,760 It will go to the 700. 108 00:07:02,850 --> 00:07:07,020 So we will reach at best seven hundred and then we will print the entire contents of the array which 109 00:07:07,020 --> 00:07:08,330 is a b c d. 110 00:07:08,620 --> 00:07:10,310 So here it is our output. 111 00:07:10,450 --> 00:07:14,630 So output is a b c v and they just run T. 112 00:07:14,680 --> 00:07:20,480 Okay so now what we did here is we changed the target index and now it becomes E. 113 00:07:20,490 --> 00:07:24,160 So ABC e it is now ABC. 114 00:07:24,360 --> 00:07:24,870 Okay. 115 00:07:25,020 --> 00:07:27,610 And here how we will call. 116 00:07:27,630 --> 00:07:37,200 We will call as to dart student so that ages party and addresses 700 similarly agent names will become 117 00:07:37,260 --> 00:07:39,010 20 and set 20. 118 00:07:39,070 --> 00:07:41,350 Sorry it will -- had 700. 119 00:07:41,520 --> 00:07:43,990 And finally S2 will look something like this. 120 00:07:44,010 --> 00:07:49,650 Ages 30 and S2 name also contains the address 700. 121 00:07:49,760 --> 00:07:50,780 Okay. 122 00:07:50,940 --> 00:07:58,570 It also contains that best 700 and this is our S2 so as to is also pointing towards this area only then 123 00:07:58,660 --> 00:08:00,300 we will print the value of S2. 124 00:08:00,400 --> 00:08:07,150 So for printing the name we will go to our number 700 and print its content so the content is ABC and 125 00:08:07,150 --> 00:08:08,520 they just 30. 126 00:08:08,800 --> 00:08:16,690 Now again we are printing S1 s under display so for us on our display we will do each S1 for printing 127 00:08:16,690 --> 00:08:17,130 the name. 128 00:08:17,140 --> 00:08:18,170 What we will do. 129 00:08:18,270 --> 00:08:23,980 We will go to the seven hundred and print the content now editor seven indeed we have ABC. 130 00:08:23,980 --> 00:08:27,720 So ABC will get printed and they each will be 20. 131 00:08:27,760 --> 00:08:30,240 So that's how ABC is coming out to be here. 132 00:08:30,250 --> 00:08:31,450 Which is wrong. 133 00:08:31,450 --> 00:08:33,830 Ideally it should be ABC. 134 00:08:34,780 --> 00:08:39,610 OK so what is happening here is both objects are pointing towards the same area. 135 00:08:39,640 --> 00:08:43,480 If we do change in one object it will reflect in the other object also. 136 00:08:43,750 --> 00:08:49,940 Okay so what we should do we should copy the end that every other then copying the ad does only. 137 00:08:50,020 --> 00:08:54,230 Okay here we are only copying that address seven that is being getting copied. 138 00:08:54,250 --> 00:08:57,740 Ideally what we should do is we should copy that Eddie. 139 00:08:57,820 --> 00:09:02,950 Okay so this copy this copy is called shallow copy. 140 00:09:02,950 --> 00:09:08,080 So what is the meaning of shallow copy shallow copy means copy only the address. 141 00:09:08,080 --> 00:09:10,420 So currently we are doing shallow copy. 142 00:09:10,530 --> 00:09:11,000 Okay. 143 00:09:11,110 --> 00:09:12,690 So whenever we pass Eddie. 144 00:09:12,700 --> 00:09:17,090 So rather than copying the entirety we copy the address of the Zulu index of dairy. 145 00:09:17,110 --> 00:09:25,800 So if we copy the address if we copy the address of Eddie then it is called shallow copy okay. 146 00:09:25,850 --> 00:09:28,820 So now let's see how to fix this problem 147 00:09:31,720 --> 00:09:34,620 see at this line this arrow age is age. 148 00:09:34,630 --> 00:09:35,070 Okay. 149 00:09:35,080 --> 00:09:36,900 So this line is absolutely correct. 150 00:09:36,910 --> 00:09:40,010 Wyatt is correct because age is then digital variable. 151 00:09:40,060 --> 00:09:42,850 So the whole values being getting copied. 152 00:09:42,850 --> 00:09:47,220 But in this case we are only copying the address. 153 00:09:47,740 --> 00:09:53,620 Okay so at a somewhere else and we have only copied the address of the z index of that diary. 154 00:09:53,680 --> 00:09:56,850 So this is called shallow copy. 155 00:09:56,950 --> 00:09:57,610 This is 156 00:10:00,480 --> 00:10:02,030 shallow copy. 157 00:10:02,410 --> 00:10:10,270 I believe we should avoid shallow copy shallow copy means copy only the address of the error a copy 158 00:10:10,270 --> 00:10:12,130 only the address of the area. 159 00:10:12,130 --> 00:10:18,130 So I believe what we should do we should create a new Eddy and then copy the entirety. 160 00:10:18,600 --> 00:10:19,310 Okay. 161 00:10:19,420 --> 00:10:23,280 We should create a new area and then copy the entire content of dairy. 162 00:10:23,380 --> 00:10:28,750 So that is called deep copy so shallow copies 163 00:10:33,530 --> 00:10:36,990 copy only address 164 00:10:39,910 --> 00:10:44,820 often zero index of the area and deep copy is 165 00:10:47,900 --> 00:10:55,630 copy DNA battery not only their address we should copy the entire area. 166 00:10:55,650 --> 00:10:57,210 Now let's see how we really do this 167 00:11:06,530 --> 00:11:10,950 so let us first of all create a new area so that we can copy the entirety. 168 00:11:10,950 --> 00:11:15,810 So we're creating the new areas in Texas like similar to this new cat. 169 00:11:16,280 --> 00:11:22,110 What it will take it will take the size of the eddy size of the this name. 170 00:11:22,330 --> 00:11:26,910 So for calculating the land we have and will function as to get alien. 171 00:11:27,050 --> 00:11:28,440 We will pass it name. 172 00:11:28,460 --> 00:11:33,840 It will give me the name it will give me the size for example the name is ABC. 173 00:11:33,890 --> 00:11:38,890 So listing land as Tierra Leon will give me for ABC SGI really intrigued me food. 174 00:11:39,500 --> 00:11:45,380 So I have to do plus one had Y plus one because we have to also copy the null corrector so for copying 175 00:11:45,380 --> 00:11:47,270 the null corrector I am doing plus one here 176 00:11:50,300 --> 00:11:50,610 okay. 177 00:11:50,630 --> 00:11:53,030 So now we have created a new Eddy. 178 00:11:53,090 --> 00:11:56,210 Now after creating the new Eddy we just have to copy the content. 179 00:11:56,330 --> 00:12:00,020 So for copying the content we have inbuilt function string copy. 180 00:12:00,050 --> 00:12:10,620 So first we have to give their destination and then we have to give the source so the sources name copy 181 00:12:16,490 --> 00:12:17,030 so. 182 00:12:17,120 --> 00:12:19,220 Copy this name into this name. 183 00:12:19,220 --> 00:12:20,180 Copy the content. 184 00:12:20,180 --> 00:12:20,410 Okay. 185 00:12:20,420 --> 00:12:22,180 So content will get copied. 186 00:12:22,190 --> 00:12:23,390 Null will also get copied. 187 00:12:23,420 --> 00:12:23,900 Okay. 188 00:12:23,900 --> 00:12:30,460 Along with content we will also copy the null and void this plus one here because we need one space. 189 00:12:30,470 --> 00:12:33,500 We need one block for copying that also. 190 00:12:33,500 --> 00:12:33,930 Okay. 191 00:12:33,980 --> 00:12:36,300 Now what will happen in this scenario. 192 00:12:36,380 --> 00:12:43,060 So the name dedicated in the mean that was containing there the 700 and the content was initially ABC 193 00:12:43,080 --> 00:12:48,520 the annual then we will call the function we will call constructor. 194 00:12:48,600 --> 00:12:53,040 So for calling the constructors and text will be like as one dot student. 195 00:12:53,250 --> 00:12:57,270 First we will pass the H and then we will pass the name. 196 00:12:57,270 --> 00:12:59,670 So name will be 700. 197 00:12:59,820 --> 00:13:03,540 So the barometer H will contain 20. 198 00:13:03,570 --> 00:13:06,480 And the barometer name will contain 700. 199 00:13:06,510 --> 00:13:07,000 Okay. 200 00:13:07,080 --> 00:13:10,450 So at this line what we are doing we are creating a new 80. 201 00:13:10,530 --> 00:13:15,120 So this name this arrow name what it will do it will create a new Eddy. 202 00:13:15,300 --> 00:13:20,970 And what will the size of the size of that is five Y five because ABC DST ideally will give me four 203 00:13:21,520 --> 00:13:22,830 and null. 204 00:13:23,220 --> 00:13:25,450 So this is four plus one. 205 00:13:25,470 --> 00:13:31,560 So we will get a new every letter that does have those wrote indexes 800 and then we what we are doing 206 00:13:31,620 --> 00:13:33,230 we are copying the content. 207 00:13:33,300 --> 00:13:36,260 So e b c b and. 208 00:13:36,780 --> 00:13:37,040 Okay. 209 00:13:37,050 --> 00:13:43,920 Now this time this arrow name and this arrow name contains 800. 210 00:13:44,060 --> 00:13:44,320 OK. 211 00:13:44,340 --> 00:13:46,220 This item name contains 800. 212 00:13:46,230 --> 00:13:52,890 So in the next step when we change the value of the name ABC when the value of name became ABC. 213 00:13:52,890 --> 00:13:58,290 And then if we again print the value of S1 so that's when name contains at does 800. 214 00:13:58,290 --> 00:13:59,890 So it will print from here. 215 00:14:00,060 --> 00:14:00,930 It will print from here. 216 00:14:00,960 --> 00:14:02,020 So what. 217 00:14:02,160 --> 00:14:03,730 So I would probably be right. 218 00:14:03,750 --> 00:14:05,310 Our output will come out to be right. 219 00:14:05,310 --> 00:14:05,830 ABC. 220 00:14:05,830 --> 00:14:06,560 The only. 221 00:14:06,570 --> 00:14:06,800 OK. 222 00:14:06,810 --> 00:14:09,780 So this is called deep copy. 223 00:14:09,840 --> 00:14:12,320 So what is the procedure for deep copy deep copy space. 224 00:14:12,330 --> 00:14:18,090 Make a new Adi which is same as the size of the this name. 225 00:14:18,090 --> 00:14:19,400 And then copy the content. 226 00:14:19,420 --> 00:14:19,690 Okay. 227 00:14:19,710 --> 00:14:22,750 Make a new Eddie make a new Eddie. 228 00:14:22,780 --> 00:14:25,140 And then copy the content. 229 00:14:25,210 --> 00:14:28,360 So in this way we will solve our problem of shallow copy. 230 00:14:28,360 --> 00:14:29,080 Now let's see. 231 00:14:30,110 --> 00:14:31,710 Okay so let us compile this file 232 00:14:35,620 --> 00:14:35,890 okay. 233 00:14:35,900 --> 00:14:41,810 So this item name is string lint so if we're using the function string England we have to include. 234 00:14:41,820 --> 00:14:44,190 I had a file called C string 235 00:14:51,520 --> 00:14:55,200 Okay so we can see here is now the output is ABC the only. 236 00:14:55,220 --> 00:14:58,850 Okay so this is called shallow copying deep copy. 237 00:14:58,850 --> 00:15:01,100 So I hope you guys understand this. 238 00:15:01,100 --> 00:15:01,430 Okay. 239 00:15:01,460 --> 00:15:01,910 Thank you.