1 00:00:01,890 --> 00:00:02,610 Hello everyone. 2 00:00:02,610 --> 00:00:07,190 So in this session we will learn a few more important concepts of object oriented programming. 3 00:00:07,200 --> 00:00:18,850 So before starting today's glass let us try something so when we write so when we write in day 5 what 4 00:00:18,850 --> 00:00:23,070 will happen we will get a memory block A and it contains the value five. 5 00:00:23,830 --> 00:00:33,520 Similarly if I want to create a budget constraint where does this index end questioned BTC. 6 00:00:33,560 --> 00:00:34,970 So at this vein what will happen. 7 00:00:34,970 --> 00:00:38,610 I will get a memory block B and it will contain five. 8 00:00:38,650 --> 00:00:42,200 Okay so we can write constants before integer or after integer. 9 00:00:42,320 --> 00:00:45,060 Okay so let's have a choice now. 10 00:00:45,110 --> 00:00:47,780 Can I break this line into two parts. 11 00:00:47,870 --> 00:00:50,090 I can make this statement and do two lines. 12 00:00:50,390 --> 00:00:54,620 So the first line is in a and the second is a S5. 13 00:00:54,710 --> 00:00:55,490 So I had this line. 14 00:00:55,520 --> 00:01:02,400 I will get a and it contains a garbage value and at this line I'm overriding the garbage value with 15 00:01:02,400 --> 00:01:03,130 the value five. 16 00:01:04,190 --> 00:01:08,190 Similarly Can I break this line into two parts and do two statements. 17 00:01:08,210 --> 00:01:14,870 So the first treatment will be I'm creating I integer constant so integer constraint B and it's second 18 00:01:14,870 --> 00:01:15,770 line. 19 00:01:15,770 --> 00:01:17,040 I will copy the value. 20 00:01:17,600 --> 00:01:19,340 So at this point what will happen. 21 00:01:19,340 --> 00:01:24,980 I will get time to Block B and it will contain I'm gonna visually enter this line. 22 00:01:24,980 --> 00:01:29,760 What we are trying to do here is we are trying to overwrite this garbage value with the value 5. 23 00:01:29,780 --> 00:01:38,150 So this line will throw us at it via error because we can see here is integer constraint we cannot change 24 00:01:38,150 --> 00:01:40,220 the value of B once it is assigned. 25 00:01:40,220 --> 00:01:45,860 So at this line B contains the garbage value B contains garbage value and at this land we are trying 26 00:01:45,860 --> 00:01:48,040 to override the garbage value with the value 5. 27 00:01:48,080 --> 00:01:50,010 So we will get an error at this line. 28 00:01:50,780 --> 00:01:54,560 So before getting error at this line we will get error at this line. 29 00:01:54,680 --> 00:01:55,620 So why an error. 30 00:01:55,640 --> 00:02:02,160 This line compiler will throw error at this line because what we are trying to do here is we are creating 31 00:02:02,160 --> 00:02:03,770 an integer constant. 32 00:02:03,930 --> 00:02:09,030 We are creating a digital content and adding digit constant contains a garbage value. 33 00:02:09,840 --> 00:02:10,120 Okay. 34 00:02:10,140 --> 00:02:15,330 So don't be a constraint on Basic garbage value basically that we lose use less what is okay since it 35 00:02:15,330 --> 00:02:16,670 contains the garbage value. 36 00:02:16,700 --> 00:02:20,390 So it is useless for us compiler will not allow us to do this. 37 00:02:20,400 --> 00:02:25,020 So what we have to do we have to initialize the constraint we have to finish that's the constraint variables 38 00:02:25,080 --> 00:02:27,180 at the time of its creation. 39 00:02:27,180 --> 00:02:28,790 Okay so this line is correct. 40 00:02:28,830 --> 00:02:32,610 We have to initialize the constraint variable at the time of its creation. 41 00:02:32,610 --> 00:02:35,190 Now let us take one more example. 42 00:02:35,190 --> 00:02:44,920 So and day is 5 so I really get my memory block I and it contains the value 5. 43 00:02:44,960 --> 00:02:49,810 Now I want to create that offense variable so of variable G is a. 44 00:02:49,930 --> 00:02:52,240 So the name of this block is also G. 45 00:02:52,450 --> 00:02:56,880 Okay so both I enjoy points to this memory location. 46 00:02:57,040 --> 00:03:00,490 Now can I break this line into two parts into two statements. 47 00:03:00,490 --> 00:03:07,690 So the first statement is create a reference variable and the second statement points to J will point 48 00:03:07,690 --> 00:03:08,380 do I. 49 00:03:08,500 --> 00:03:11,190 Okay so again what will happen. 50 00:03:11,190 --> 00:03:12,150 We will get better. 51 00:03:12,180 --> 00:03:19,530 This line so just like the constant variables it is compulsory to give the value of a reference variable 52 00:03:19,530 --> 00:03:20,970 at the time of its creation. 53 00:03:20,970 --> 00:03:28,130 Okay so at this line what will happen it will contain it will point to a garbage memory location okay 54 00:03:28,160 --> 00:03:30,920 so compiler will not allow us to do this. 55 00:03:30,980 --> 00:03:37,910 Okay so for constraint and for reference variable for constraint and for reference variable we have 56 00:03:37,910 --> 00:03:43,930 to give their value at the time of their creation at the time of the memory allocation okay. 57 00:03:43,940 --> 00:03:44,960 Now let's see in code 58 00:03:51,150 --> 00:03:52,680 so I have a class here. 59 00:03:52,680 --> 00:03:56,630 Student So this student contains two public properties each and William. 60 00:03:56,630 --> 00:03:58,890 But now my aim is very simple. 61 00:03:58,890 --> 00:04:02,820 What I want is what we want is once the roll number is set. 62 00:04:02,880 --> 00:04:06,510 It cannot be changed similarly. 63 00:04:06,510 --> 00:04:12,490 So what we have to do here if we write C++ then it will throw at it. 64 00:04:12,780 --> 00:04:17,100 It will throw Error because B's in beta constant B's integer constant. 65 00:04:17,100 --> 00:04:22,770 Similarly my aim is once the value of the lumber is set but the value of raw lumber is set. 66 00:04:23,190 --> 00:04:24,600 I cannot change it. 67 00:04:24,630 --> 00:04:30,060 So what we have to do we have to make it IPG constant so we can write construct before integer or after 68 00:04:30,060 --> 00:04:30,510 ingredient. 69 00:04:30,510 --> 00:04:35,720 So here I am writing question before integer okay. 70 00:04:36,010 --> 00:04:44,810 Now let us create objects so student S1 not a desk tried to change the values of a general number. 71 00:04:44,840 --> 00:04:55,110 Okay so as one dot age lets certain and S1 DOT rule number let's say hundred. 72 00:04:55,110 --> 00:04:57,120 Okay so let us win this fight. 73 00:04:57,570 --> 00:05:03,120 What will happen at this line there will be an edit and because we are trying to change the rules. 74 00:05:03,140 --> 00:05:05,570 But okay so let us first read the file and see that it 75 00:05:10,250 --> 00:05:15,530 so would you indicate then that it why probably we didn't run this file. 76 00:05:15,950 --> 00:05:16,990 Yes. 77 00:05:17,330 --> 00:05:22,200 Okay now we will read this file again well guess what we get an error at this line. 78 00:05:22,260 --> 00:05:24,390 Now let us try to understand why we get an added 79 00:05:30,850 --> 00:05:31,600 so at this line. 80 00:05:31,600 --> 00:05:32,910 What will happen. 81 00:05:33,070 --> 00:05:36,970 Default constructed will be called default in the constructor. 82 00:05:37,690 --> 00:05:38,040 Okay. 83 00:05:38,080 --> 00:05:45,890 So default and built constructor will get called and what it will do age. 84 00:05:45,890 --> 00:05:49,830 Rule number both will be set to garbage value. 85 00:05:50,020 --> 00:05:52,480 So a general number both contingent garbage value. 86 00:05:52,510 --> 00:05:56,530 So this is to rent then that's when they both contain garbage values. 87 00:05:57,100 --> 00:05:57,660 Okay. 88 00:05:57,790 --> 00:05:58,810 Add this line. 89 00:05:58,900 --> 00:06:01,590 What I am trying to do I am making. 90 00:06:01,740 --> 00:06:06,390 I am overwriting the garbage value of the age to pen and add this line. 91 00:06:06,390 --> 00:06:07,790 I am overwriting. 92 00:06:08,020 --> 00:06:12,410 I am writing this garbage value and I am trying to make a hundred. 93 00:06:12,520 --> 00:06:14,110 But you cannot do this. 94 00:06:14,120 --> 00:06:14,800 Why. 95 00:06:14,870 --> 00:06:17,550 Because rule number is a constraint. 96 00:06:17,560 --> 00:06:23,260 If you see the glass if you show the glass we have make it in PJM constant since all lumber is in digit 97 00:06:23,260 --> 00:06:24,140 constant. 98 00:06:24,220 --> 00:06:26,680 Once it creates a value we cannot tolerate it. 99 00:06:27,100 --> 00:06:29,630 So here we cannot tolerate this garbage value. 100 00:06:29,740 --> 00:06:36,700 But if we will see we get an error at line number six why we go down a red line number six because what 101 00:06:36,700 --> 00:06:41,380 we are trying to do here is we are creating we are creating a rule number we are creating and digital 102 00:06:41,380 --> 00:06:43,760 constraint which will contain the garbage value. 103 00:06:43,900 --> 00:06:46,180 So compiler will not allow us to do this. 104 00:06:46,750 --> 00:06:54,560 So basically what compiler will say if these integer constant and this integer constant contains some 105 00:06:54,570 --> 00:06:59,470 garbage value then basically it's useless it's useless to make integer constraint. 106 00:06:59,530 --> 00:07:03,720 Okay so that's why we will get it at line number 6. 107 00:07:03,790 --> 00:07:05,910 We will also get in that red line number eight. 108 00:07:06,130 --> 00:07:09,340 But before line number it we will get that red line number six. 109 00:07:09,970 --> 00:07:14,830 Okay so it is amended to do initialize the rule number at the time of its creation at the time of memory 110 00:07:14,830 --> 00:07:15,610 allocation. 111 00:07:15,610 --> 00:07:22,150 Okay so the one way to correct that one for the one way to correct that record is what we will do we 112 00:07:22,150 --> 00:07:23,010 have to initialize. 113 00:07:23,020 --> 00:07:25,240 So let's make a hundred here now. 114 00:07:25,370 --> 00:07:26,620 There is a problem. 115 00:07:26,650 --> 00:07:27,850 So what is the problem. 116 00:07:27,850 --> 00:07:30,000 Suppose I have tends to rinse. 117 00:07:30,010 --> 00:07:31,190 Then what will happen. 118 00:07:31,270 --> 00:07:35,540 All that tends to advance will have the roll number is handed and they cannot change it. 119 00:07:35,620 --> 00:07:37,680 So obviously this is a wrong approach. 120 00:07:37,690 --> 00:07:39,660 This is a wrong method. 121 00:07:39,700 --> 00:07:41,760 Okay so what we should do. 122 00:07:41,890 --> 00:07:47,100 So where to initialize so that each object can have its different number of each object can have different 123 00:07:47,190 --> 00:07:47,830 number. 124 00:07:47,830 --> 00:07:53,500 So the answer is constructor y constructor because constructor is called for each object and construct 125 00:07:53,500 --> 00:07:55,180 will be called on live once. 126 00:07:55,270 --> 00:07:57,610 Okay so let us create a constructor 127 00:08:02,150 --> 00:08:03,130 so we will construct. 128 00:08:03,170 --> 00:08:06,010 We will create a better matrix constructor it will take. 129 00:08:06,030 --> 00:08:12,920 Rule number as input and then we will set rule number do. 130 00:08:13,830 --> 00:08:23,200 Okay now let us run this file see we are again getting an error so let us try to understand why we get 131 00:08:23,200 --> 00:08:23,640 in it at 132 00:08:30,000 --> 00:08:30,930 so when I write 133 00:08:34,060 --> 00:08:36,420 it a and in the next line. 134 00:08:36,610 --> 00:08:38,260 If I write a equals five. 135 00:08:38,800 --> 00:08:40,790 So at this line what will happen. 136 00:08:40,850 --> 00:08:45,360 So before a I am not writing and Deja before I am not writing Deja. 137 00:08:45,400 --> 00:08:46,540 So what does this mean. 138 00:08:46,540 --> 00:08:51,790 This means that is already created and the memory is already kicked into the memory which contains the 139 00:08:51,790 --> 00:08:55,850 garbage value and we are trying to override this garbage value. 140 00:08:56,060 --> 00:09:02,120 Okay now we see this line rhodium but it goes out we are not writing in Egypt before William but so 141 00:09:02,120 --> 00:09:07,270 that means that William has already been created in the memory and it contains the guide of base value. 142 00:09:07,280 --> 00:09:13,960 And here we are trying to put odd R in doodle lumber and lumber contains garbage value since all lumber 143 00:09:13,960 --> 00:09:21,200 is St. PJ constant we can not tolerate garbage failure without Okay so that's why we are getting added 144 00:09:21,280 --> 00:09:23,340 at this lane. 145 00:09:23,520 --> 00:09:30,570 Okay so what happened is as soon as we entered the constructor as soon as we each line number seven 146 00:09:31,680 --> 00:09:36,750 rule number is already created in the memory and it contains garbage value. 147 00:09:36,750 --> 00:09:38,250 So what is the solution. 148 00:09:38,280 --> 00:09:43,180 The solution is we have to initialize the rule number at the time of memory allocation. 149 00:09:43,230 --> 00:09:48,840 We cannot do it inside the constructor because as soon as we reach inside the constructor memories are 150 00:09:48,840 --> 00:09:52,840 allocated and garbage based Ray Lewis present at the memory location. 151 00:09:52,860 --> 00:09:58,020 Okay so what we can use here is there is something called initialization list 152 00:10:01,490 --> 00:10:04,850 initialization list can help us here. 153 00:10:04,850 --> 00:10:06,800 Okay so let's 1 again see. 154 00:10:06,830 --> 00:10:07,870 What is the problem. 155 00:10:07,880 --> 00:10:09,220 So the problem is very simple. 156 00:10:09,230 --> 00:10:16,250 As soon as we reach line number seven as soon as we reach inside the constructor the roll number this 157 00:10:16,250 --> 00:10:21,020 roll number property this roll number that a member has already been doing to the memory and it contains 158 00:10:21,110 --> 00:10:24,940 a garbage value and add line number seven and line number seven. 159 00:10:24,950 --> 00:10:30,190 We are trying to override this garbage value with ADD okay and we cannot do this. 160 00:10:30,190 --> 00:10:30,430 Why. 161 00:10:30,460 --> 00:10:32,710 Because a number is in beta constraint. 162 00:10:32,780 --> 00:10:35,000 We cannot change the values. 163 00:10:35,120 --> 00:10:37,490 We cannot change the value through a number. 164 00:10:37,490 --> 00:10:37,910 Okay. 165 00:10:38,030 --> 00:10:45,150 So the solution is initialization list so what initialization will do. 166 00:10:45,210 --> 00:10:49,680 It will initialize the constraint properties at the time of memory allocation. 167 00:10:49,680 --> 00:10:51,000 Now let's see this index 168 00:10:53,660 --> 00:10:56,050 so first of all this is wrong. 169 00:10:56,150 --> 00:11:02,240 Let us come into this code and this index for initialization list syntax for using initialization list 170 00:11:02,240 --> 00:11:03,620 is very simple. 171 00:11:03,680 --> 00:11:13,630 Put a column and then name of the name of the bat and we did the argument which is odd. 172 00:11:13,810 --> 00:11:14,080 Okay. 173 00:11:14,080 --> 00:11:14,800 And that's all. 174 00:11:15,270 --> 00:11:15,510 Okay. 175 00:11:15,520 --> 00:11:16,880 So let us win this fight. 176 00:11:18,320 --> 00:11:20,840 See now this time there is no edit. 177 00:11:20,960 --> 00:11:22,550 Okay so what is happening here is 178 00:11:27,530 --> 00:11:33,140 so I told you when we will reach line number seven rule number property is already being created in 179 00:11:33,140 --> 00:11:34,270 the memory. 180 00:11:34,490 --> 00:11:36,020 Now see line number six. 181 00:11:36,020 --> 00:11:37,160 So what will happen I like. 182 00:11:37,340 --> 00:11:39,460 So what will happen at line number six. 183 00:11:39,500 --> 00:11:45,000 We can assume that rule number is given memory at line number six. 184 00:11:45,020 --> 00:11:48,550 Rule number is given memory and add the line number six. 185 00:11:48,560 --> 00:11:50,480 We are writing this statement. 186 00:11:50,630 --> 00:11:53,480 So this rule number will contain R okay. 187 00:11:53,630 --> 00:11:59,710 So this way we can initialize our private properties week initialize have a constant private properties. 188 00:11:59,840 --> 00:12:07,900 So at this line we can say what is happening constant in integer rule number 189 00:12:11,400 --> 00:12:12,570 equals out. 190 00:12:12,630 --> 00:12:14,380 So this is the meaning of this line. 191 00:12:14,450 --> 00:12:15,100 Okay. 192 00:12:15,100 --> 00:12:21,450 Memories being allocated to General Lambert and the OT is initialized and this is and rule number and 193 00:12:21,450 --> 00:12:26,280 rule number of private properties initialized with that. 194 00:12:26,320 --> 00:12:28,510 Okay so this is the use of initialization list. 195 00:12:33,270 --> 00:12:38,730 Okay so what we can do here is it is not necessary to take an integer as input. 196 00:12:38,730 --> 00:12:43,530 We can also set the value as we can also write it like hundred but also. 197 00:12:43,530 --> 00:12:44,520 This is of no use. 198 00:12:44,520 --> 00:12:51,570 This is useless by useless because every object will have the roll number hundred okay every object 199 00:12:51,570 --> 00:12:53,740 will have rule number hundred. 200 00:12:53,760 --> 00:13:00,930 So obviously this is useless now what if I take two parameters hasn't put a general number so in total 201 00:13:00,930 --> 00:13:04,130 number and the second values and each. 202 00:13:04,170 --> 00:13:16,120 Okay so rule number are and then comma each is a okay so. 203 00:13:16,180 --> 00:13:21,260 So we should notice here is initialization list can also be used for normal variables. 204 00:13:21,270 --> 00:13:23,130 Normal integer variables. 205 00:13:23,130 --> 00:13:23,580 Okay. 206 00:13:23,640 --> 00:13:28,380 It can also be used for normal properties so it is not necessary. 207 00:13:28,530 --> 00:13:33,360 It is not compulsory that initialization list can only be used for constant data members. 208 00:13:33,450 --> 00:13:36,750 Okay initialization list can be used for normal data members. 209 00:13:37,340 --> 00:13:37,830 Okay. 210 00:13:38,010 --> 00:13:46,560 Now what will happen if I change the argument name to each so we have to write aged 211 00:13:50,390 --> 00:13:50,890 okay. 212 00:13:50,990 --> 00:13:51,860 So this is correct. 213 00:13:51,860 --> 00:13:56,210 There is no need to write this way because it is very clear. 214 00:13:57,680 --> 00:14:08,020 It is very clear here that this age means this at age and this age is the argument age so there is no 215 00:14:08,020 --> 00:14:09,180 confusion here. 216 00:14:09,190 --> 00:14:12,600 Everything is very clear so there is no need to write this here. 217 00:14:13,270 --> 00:14:17,010 Okay so there is no confusion since there is no confusion. 218 00:14:17,110 --> 00:14:24,320 We do not need to write this okay so one more case where the initialization list can be used is suppose 219 00:14:24,320 --> 00:14:29,450 we have a reference variable let us have a reference variable. 220 00:14:29,480 --> 00:14:40,030 Okay so offense variable X so this X is e.g. defense easy reference variable 221 00:14:45,860 --> 00:14:53,110 Okay so initialization list can also be used for reference variables to what we want is our aim is very 222 00:14:53,110 --> 00:14:53,530 simple 223 00:14:59,020 --> 00:14:59,830 so we've warned 224 00:15:03,590 --> 00:15:04,640 this. 225 00:15:04,730 --> 00:15:07,990 So this is our home okay. 226 00:15:08,360 --> 00:15:16,440 But it cannot write like this way because this H if you see here this age can be argument page. 227 00:15:16,610 --> 00:15:17,950 So there is a confusion here. 228 00:15:17,960 --> 00:15:26,470 Since there is confusion we have to write something like this this arrow each so at this line. 229 00:15:26,510 --> 00:15:29,730 There was confusion that age can be the argument age. 230 00:15:29,750 --> 00:15:32,960 So to avoid the confusion we will write this. 231 00:15:33,050 --> 00:15:33,290 Okay. 232 00:15:33,290 --> 00:15:35,450 So writing this is mandatory here. 233 00:15:36,470 --> 00:15:39,560 And I told you so I told you before. 234 00:15:39,560 --> 00:15:45,890 Just like the constraint variables reference variables have to be initialized at the time of its creation. 235 00:15:46,030 --> 00:15:54,480 Okay so it is mandatory that we have to use initialization list for reference variables so X and the 236 00:15:54,480 --> 00:15:56,610 value will be this arrow each 237 00:15:59,660 --> 00:16:00,800 okay. 238 00:16:00,920 --> 00:16:01,970 Now let us in this file 239 00:16:07,200 --> 00:16:12,450 now obviously as we write our own parameters constructor default constructor is not available to us 240 00:16:12,450 --> 00:16:12,890 anymore. 241 00:16:13,710 --> 00:16:16,440 So we have to use parameters constructor. 242 00:16:16,440 --> 00:16:20,410 So let's say that rule number is a hundred and let's say the easiest 10. 243 00:16:20,850 --> 00:16:21,520 Okay. 244 00:16:21,690 --> 00:16:23,340 So obviously this line will not work 245 00:16:26,150 --> 00:16:27,990 because when somebody is a constant property. 246 00:16:28,520 --> 00:16:33,430 Okay now let us on this file and they should be noted okay. 247 00:16:33,440 --> 00:16:34,710 So our code is running. 248 00:16:34,750 --> 00:16:37,420 There is no added. 249 00:16:37,640 --> 00:16:44,050 So what we learned in this session there's is something called initialization list. 250 00:16:46,520 --> 00:16:50,210 And what is the purpose of initialization list. 251 00:16:50,260 --> 00:16:52,350 The purpose is very easy. 252 00:16:52,560 --> 00:16:53,380 It initialize 253 00:16:56,550 --> 00:17:06,030 constraint properties constraint data members constraint properties and the defense's data member and 254 00:17:06,030 --> 00:17:09,250 reference properties at the time 255 00:17:12,220 --> 00:17:13,910 and their time of memory allocation 256 00:17:19,680 --> 00:17:20,630 okay. 257 00:17:20,700 --> 00:17:23,010 So I hope you have understood this video. 258 00:17:23,160 --> 00:17:23,620 Okay. 259 00:17:23,700 --> 00:17:24,110 Thank you.