1 00:00:02,170 --> 00:00:02,890 Hello everyone. 2 00:00:02,890 --> 00:00:06,030 So in this video I want to discuss about inheritance. 3 00:00:06,380 --> 00:00:06,690 OK. 4 00:00:06,730 --> 00:00:09,040 So what is the meaning of inheritance. 5 00:00:09,130 --> 00:00:14,210 So inheritance means to inherit some properties from our parents or ancestors. 6 00:00:14,260 --> 00:00:14,710 OK. 7 00:00:14,800 --> 00:00:20,440 So just like we humans do what we do we all inherit some correct districts from our parents or grandparents 8 00:00:20,740 --> 00:00:23,100 and some properties or qualities are our own. 9 00:00:23,590 --> 00:00:25,320 OK so let's say in code. 10 00:00:25,420 --> 00:00:27,160 So suppose I have three classes 11 00:00:30,740 --> 00:00:34,820 bicycle and I have a class truck. 12 00:00:34,990 --> 00:00:35,570 Okay. 13 00:00:35,600 --> 00:00:44,870 So the properties of car class are color color of the car maximum speed of the car and let's say the 14 00:00:44,870 --> 00:00:46,640 number of gears. 15 00:00:46,640 --> 00:00:46,900 Okay. 16 00:00:46,940 --> 00:00:55,160 So number of gears and louder let's talk about the properties of bicycle to color of the bicycle max 17 00:00:55,160 --> 00:01:00,030 speed and obviously bicycle doesn't have gears. 18 00:01:00,030 --> 00:01:02,670 So let's say we have a billion property is for level. 19 00:01:02,690 --> 00:01:04,530 So some bicycle s for level. 20 00:01:04,620 --> 00:01:06,110 So we have a property billion. 21 00:01:06,150 --> 00:01:08,060 Property is for level. 22 00:01:08,100 --> 00:01:08,590 Okay. 23 00:01:08,670 --> 00:01:10,600 Now let us talk about truck. 24 00:01:10,620 --> 00:01:21,330 So conserve the truck max speed of their truck and some other drug related properties okay. 25 00:01:21,470 --> 00:01:25,640 So what is happening here is some properties are common in many classes. 26 00:01:25,640 --> 00:01:25,950 Okay. 27 00:01:25,980 --> 00:01:30,850 So common common and common. 28 00:01:31,470 --> 00:01:31,880 Okay. 29 00:01:31,930 --> 00:01:37,090 So these properties and some properties are common in many classes because they all have one feature 30 00:01:37,090 --> 00:01:40,390 in common all three belongs to vehicle. 31 00:01:40,390 --> 00:01:40,680 Okay. 32 00:01:40,690 --> 00:01:42,400 All three are vehicle. 33 00:01:42,460 --> 00:01:48,980 So what is happening here is so I have a class vehicle. 34 00:01:49,330 --> 00:01:59,090 So all the three things car bicycle and truck they all have one feature in common. 35 00:01:59,110 --> 00:02:00,940 All three are vehicles. 36 00:02:01,030 --> 00:02:01,720 Okay. 37 00:02:01,780 --> 00:02:07,530 So now my aim is I have to create these three classes okay. 38 00:02:07,560 --> 00:02:09,660 So I have to create three classes 39 00:02:12,350 --> 00:02:13,670 guide bicycle and truck. 40 00:02:14,180 --> 00:02:17,840 So the first race just like we created these classes. 41 00:02:17,900 --> 00:02:21,680 So the first race we will create classes in this manner. 42 00:02:21,680 --> 00:02:25,640 First some common properties then candidate properties. 43 00:02:25,640 --> 00:02:29,810 Then again some common properties then bicycle related properties. 44 00:02:29,810 --> 00:02:33,990 Again some common properties and then regulated properties. 45 00:02:34,010 --> 00:02:34,550 Okay. 46 00:02:34,610 --> 00:02:40,150 Now the second way to create these three classes in a good way in a in an appropriate way. 47 00:02:40,350 --> 00:02:41,770 It is what we will do. 48 00:02:41,840 --> 00:02:50,810 We will move these properties inside difficult class okay so that we could class will have color and 49 00:02:50,810 --> 00:02:53,600 the vehicle will obviously have the max speed. 50 00:02:54,380 --> 00:02:54,650 Okay. 51 00:02:54,650 --> 00:02:55,940 And we will remove it from here. 52 00:02:56,390 --> 00:02:56,650 Okay. 53 00:02:56,660 --> 00:02:59,630 So remove these things from the bicycle class. 54 00:02:59,660 --> 00:03:05,150 Remove the common properties from the track class okay. 55 00:03:05,180 --> 00:03:06,000 So we have to move. 56 00:03:06,000 --> 00:03:07,880 Common properties to difficult class. 57 00:03:07,890 --> 00:03:15,990 So vehicle is our parent vehicle is our parent class and car is a child. 58 00:03:16,080 --> 00:03:23,500 Child class bicycle is a child class truck is a child a class okay. 59 00:03:23,540 --> 00:03:30,500 So what really happened that car class will have some kind of specific properties and the common properties 60 00:03:30,560 --> 00:03:33,230 it will inherit from its parent. 61 00:03:33,830 --> 00:03:34,150 Okay. 62 00:03:34,180 --> 00:03:40,100 Similarly bicycle will have some properties of its own bicycle later properties and other properties 63 00:03:40,220 --> 00:03:42,030 it will inherit from vehicle. 64 00:03:42,200 --> 00:03:47,840 Similarly truck will have some percolated properties truck specific properties and the common properties 65 00:03:48,080 --> 00:03:52,110 it will inherit from its parent that is difficult class. 66 00:03:52,160 --> 00:03:52,570 Okay. 67 00:03:52,640 --> 00:03:55,600 Now suppose I want to create one more class here. 68 00:03:55,760 --> 00:03:57,500 Okay so I want to create one more class. 69 00:03:57,500 --> 00:04:04,460 Let's say the name of the class is bike so the name of the classes bike. 70 00:04:04,510 --> 00:04:05,950 Now what bike will do. 71 00:04:06,130 --> 00:04:13,840 It will inherit some common properties it will inherit color and the max speed from the vehicle class 72 00:04:14,230 --> 00:04:18,140 and some properties will be related to the bike specific properties. 73 00:04:18,730 --> 00:04:23,570 Okay so the second way is the most appropriate way to create classes. 74 00:04:23,620 --> 00:04:25,010 Okay so whatever approach. 75 00:04:25,140 --> 00:04:25,480 Move. 76 00:04:25,480 --> 00:04:33,730 Common properties to a common class to one class create one class which is the parent of all the classes 77 00:04:34,030 --> 00:04:36,370 and move the common properties there. 78 00:04:36,370 --> 00:04:36,730 Okay. 79 00:04:37,890 --> 00:04:41,990 So let us take one more example to understand it better. 80 00:04:43,570 --> 00:04:53,210 OK so suppose I ever teach a class and I have a student class teacher class end student class. 81 00:04:53,230 --> 00:04:55,990 So now let us talk about some properties of the teacher. 82 00:04:56,170 --> 00:05:01,360 So teacher will have a name age of the teacher will be a property. 83 00:05:01,420 --> 00:05:03,970 Similarly address contact number 84 00:05:07,750 --> 00:05:16,750 and let's say qualifications without the qualification of their teacher expertise area. 85 00:05:16,890 --> 00:05:19,150 So these are some properties of a teacher. 86 00:05:19,170 --> 00:05:21,660 Now let us talk about the properties of the student. 87 00:05:21,660 --> 00:05:29,130 So a student will have a name and will have age similarly address contact number 88 00:05:32,240 --> 00:05:33,140 a student will have. 89 00:05:33,140 --> 00:05:40,220 Rule number badge number and so on. 90 00:05:40,290 --> 00:05:49,870 Okay so now we can see here again some properties are common name age address contact number and here 91 00:05:49,900 --> 00:05:53,570 also some properties are common. 92 00:05:53,830 --> 00:05:57,370 Okay so now what we will do we have learned about inheritance. 93 00:05:57,370 --> 00:05:58,740 We will create a new class. 94 00:05:58,750 --> 00:06:06,020 We will create one class let's say the name of this class is human class. 95 00:06:06,290 --> 00:06:12,520 We will move the common properties here and we will remove the common properties from here okay. 96 00:06:12,530 --> 00:06:17,280 So remove the common properties because the common properties will now belong to human class. 97 00:06:17,380 --> 00:06:21,410 So all human will have name it will have each. 98 00:06:21,770 --> 00:06:24,920 It will have address and it will have contact number 99 00:06:28,830 --> 00:06:29,020 so. 100 00:06:29,040 --> 00:06:32,860 Teacher class will contain only teacher specific properties. 101 00:06:32,860 --> 00:06:38,210 Student class will contain only student specific properties and all the other properties. 102 00:06:38,230 --> 00:06:38,950 What it will do. 103 00:06:38,980 --> 00:06:41,280 It will inherit from its parent. 104 00:06:42,190 --> 00:06:46,600 Okay so we will inherit the common properties from our parents. 105 00:06:46,600 --> 00:06:52,090 Again we will inherit some properties from our parents and some properties will be our own. 106 00:06:52,900 --> 00:07:02,550 Okay so we are inheriting common properties Okay so human is our patent class human is our parent and 107 00:07:02,700 --> 00:07:04,320 teacher and student. 108 00:07:04,380 --> 00:07:05,670 They both had a child. 109 00:07:05,680 --> 00:07:08,420 Child classes okay. 110 00:07:08,570 --> 00:07:10,310 So what is the main purpose. 111 00:07:10,310 --> 00:07:13,290 What is the main benefit of using inheritance. 112 00:07:14,780 --> 00:07:19,430 So the main benefit of using inheritance is reusing the called 113 00:07:23,380 --> 00:07:25,150 We are reusing the code. 114 00:07:25,150 --> 00:07:32,820 Okay so move all the common things at one place and whenever that common thing is acquired just inherited 115 00:07:32,850 --> 00:07:34,050 the common properties. 116 00:07:34,050 --> 00:07:38,820 Okay so this is the main benefit of using inheritance reusing the gold. 117 00:07:38,820 --> 00:07:39,100 Okay. 118 00:07:39,120 --> 00:07:45,780 We will just write the code once and if someone wants those properties just inherit the properties. 119 00:07:45,810 --> 00:07:46,070 Okay. 120 00:07:46,110 --> 00:07:49,920 So the main benefit of inheritances reusing the code 121 00:07:52,860 --> 00:07:53,350 okay. 122 00:07:53,420 --> 00:07:57,730 Now let's talk about excess modifiers. 123 00:07:57,780 --> 00:08:00,150 Now let's talk about excess modifiers 124 00:08:03,560 --> 00:08:08,820 so we already know about to excess modifiers public and private. 125 00:08:09,140 --> 00:08:16,100 So we have already started about private and we have already started about public so private means it 126 00:08:16,100 --> 00:08:22,460 is not accessible outside the class and public means it is accessible to anyone outside the class. 127 00:08:22,460 --> 00:08:25,130 Okay so they both are very extreme. 128 00:08:25,130 --> 00:08:29,420 Private is very strong and public is very lenient okay. 129 00:08:29,420 --> 00:08:37,550 So we want something in between and there is something in between the public and private is called protected. 130 00:08:37,670 --> 00:08:38,140 Okay. 131 00:08:38,240 --> 00:08:39,800 So what is protected. 132 00:08:39,800 --> 00:08:40,570 So what will happen. 133 00:08:40,580 --> 00:08:47,700 Let's say I have a class and inside the class if I declare a property X to be a protected property. 134 00:08:47,730 --> 00:08:48,830 So what will happen. 135 00:08:48,870 --> 00:08:56,790 So this protected property is accessible to someone outside the class and is not accessible to the others. 136 00:08:56,880 --> 00:08:57,550 Okay. 137 00:08:57,720 --> 00:09:04,620 So if I declare a property X a protected property for this protected property will be accessible outside 138 00:09:04,620 --> 00:09:11,150 the class for only for some people and for that it will not be accessible okay. 139 00:09:11,310 --> 00:09:18,210 So X is a property I've owned the property that would be accessible for some person and not accessible 140 00:09:18,240 --> 00:09:19,320 for the rest of the world. 141 00:09:19,560 --> 00:09:22,280 So we will declare that property as a protected property. 142 00:09:22,590 --> 00:09:31,020 Okay so let's say I have two classes Class A and Class B Class A is a parent class and class B is a 143 00:09:31,020 --> 00:09:33,300 child's class. 144 00:09:33,780 --> 00:09:34,070 Okay. 145 00:09:34,080 --> 00:09:36,490 So B inherit some property from me. 146 00:09:36,510 --> 00:09:38,860 Okay so let us take the call in God. 147 00:09:39,090 --> 00:09:40,890 So I have vehicle and God. 148 00:09:40,920 --> 00:09:42,030 So God is a child. 149 00:09:42,030 --> 00:09:44,760 Class and vehicle is a parent. 150 00:09:44,760 --> 00:09:51,620 Class Okay so God will inherit some of its properties from the vehicle class. 151 00:09:51,750 --> 00:09:58,170 Okay so what will happen if a property is protected then it is only accessible to child class. 152 00:09:58,380 --> 00:09:59,970 So let us take an example. 153 00:10:03,220 --> 00:10:07,270 So suppose this is working class and inside the working class. 154 00:10:07,480 --> 00:10:10,770 I have declared a property X as a protected property. 155 00:10:10,900 --> 00:10:11,680 So what will happen. 156 00:10:11,700 --> 00:10:19,200 So this protected property X is accessible outside the class but only for those classes which inherit 157 00:10:19,230 --> 00:10:20,820 from the vehicle class. 158 00:10:20,820 --> 00:10:28,710 Okay so this protected property X is accessible outside the class but only for those classes which inherit 159 00:10:28,800 --> 00:10:29,910 from vehicle class. 160 00:10:29,970 --> 00:10:33,450 That is only the child classes of the class. 161 00:10:33,870 --> 00:10:35,940 Okay so what I am saying is. 162 00:10:36,150 --> 00:10:44,790 So what I am saying here is let's say I have a vehicle class so I have a class vehicle inside the vehicle. 163 00:10:44,800 --> 00:10:54,700 I have a public property X Y and Z so access public values private and Z is protected 164 00:10:58,400 --> 00:11:00,800 and this is outside. 165 00:11:01,430 --> 00:11:07,710 Okay so public property X anyone can access public property X outside the class. 166 00:11:07,940 --> 00:11:08,340 Okay. 167 00:11:08,420 --> 00:11:10,840 X is accessible for everyone okay. 168 00:11:10,880 --> 00:11:18,950 Anyone can access anyone can access X because X is a public property outside the class private property 169 00:11:18,950 --> 00:11:27,050 y no one can access the private property why outside the class protected properties and it is accessible 170 00:11:27,110 --> 00:11:36,200 outside the class but using only roads child classes using only its child classes 171 00:11:39,760 --> 00:11:40,160 okay. 172 00:11:40,290 --> 00:11:47,040 So public property X anyone can access outside the class no one can access outside the class it is accessible 173 00:11:47,040 --> 00:11:48,850 outside the class but using only it. 174 00:11:48,860 --> 00:11:58,960 Child classes Okay so suppose this is our vehicle class and there are three other classes which I inherited 175 00:11:58,960 --> 00:12:03,500 from the working class and these are car is a child class of vehicle. 176 00:12:03,670 --> 00:12:08,960 Bicycle is also the child class of vehicle and truck is also the child the class of vehicle. 177 00:12:08,980 --> 00:12:17,880 Similarly let's say I have a class human so a human teacher and student inherits from human. 178 00:12:18,100 --> 00:12:28,920 Okay now let's talk about protected properties and okay so obviously vehicle can access the protected 179 00:12:28,920 --> 00:12:32,650 properties and God can access the protected property. 180 00:12:32,670 --> 00:12:38,570 Bicycle can access that and truck can access it and why because the oil out of child classes or difficult 181 00:12:38,600 --> 00:12:45,540 class so human cannot access that teacher cannot access it and student cannot access it. 182 00:12:45,720 --> 00:12:52,490 Okay so this is human cannot access student cannot access and teacher cannot access the protected property. 183 00:12:52,530 --> 00:12:54,890 Z of the class. 184 00:12:54,900 --> 00:13:00,720 Okay so if you want to access the protected property there should be a relation between the parent class 185 00:13:00,720 --> 00:13:01,770 and the child class. 186 00:13:01,800 --> 00:13:02,730 Okay. 187 00:13:03,160 --> 00:13:10,110 So I hope you know what is protected now so protected properties only accessible using. 188 00:13:10,110 --> 00:13:17,760 Child classes okay since human does not have any relation with the vehicle so it cannot access Z if 189 00:13:17,760 --> 00:13:23,580 human cannot exist then obviously teacher and student those who cannot access okay. 190 00:13:23,910 --> 00:13:24,330 Thank you.