1 00:00:01,730 --> 00:00:02,360 Hi everyone. 2 00:00:02,360 --> 00:00:06,590 So in this lesson we will learn how to read from a file. 3 00:00:06,650 --> 00:00:09,480 So for example this is your file. 4 00:00:09,800 --> 00:00:13,840 My file not the 60 and let's say it is containing somebody down. 5 00:00:13,880 --> 00:00:21,180 So let's say this containing Hello World and then let's say it is containing integer 5. 6 00:00:21,440 --> 00:00:25,430 So this is the date that at this present in this fight my file not the 60. 7 00:00:25,490 --> 00:00:28,420 So for reading the detail from this fight again. 8 00:00:28,430 --> 00:00:33,410 So first of all we have to include the file so hash include file stream. 9 00:00:35,000 --> 00:00:37,240 So this is my domain. 10 00:00:37,250 --> 00:00:44,180 Now what I have to do so basically first of all we have to create the object of if stream class i.e. 11 00:00:44,400 --> 00:00:50,730 if a stream input file is stream class let's say the name of the object is in fine. 12 00:00:50,790 --> 00:00:54,140 We're digging can do so you will call the concept and you will give the file name. 13 00:00:54,180 --> 00:00:59,150 So my file not the 60. 14 00:00:59,170 --> 00:01:01,570 Now one important thing it is basically Liesel. 15 00:01:01,570 --> 00:01:03,380 This file my file not the 60. 16 00:01:03,670 --> 00:01:09,660 So this file must exist because it will not create a new file. 17 00:01:09,670 --> 00:01:13,930 Now there is one more way to open the file so first is during the constructor. 18 00:01:13,930 --> 00:01:16,690 Second is basically you create an object. 19 00:01:16,690 --> 00:01:23,590 So let's say if stream the object is in file two and there's a function open. 20 00:01:23,590 --> 00:01:24,820 So what you gonna do. 21 00:01:24,820 --> 00:01:31,150 You can call the function open so inviting to dot open and then you can give the name of the file the 22 00:01:31,150 --> 00:01:32,890 file that you want to open. 23 00:01:32,890 --> 00:01:38,620 So I want to open this file and the name is my filing not the 60. 24 00:01:38,650 --> 00:01:41,780 So there are two ways of opening the file first is using deconstruct. 25 00:01:41,920 --> 00:01:46,720 Second is basically using the open function simple now. 26 00:01:46,990 --> 00:01:50,470 So there might be a situation that my file does not exist. 27 00:01:50,470 --> 00:01:51,220 So what will happen. 28 00:01:51,220 --> 00:01:53,160 You can write if condition. 29 00:01:53,200 --> 00:01:53,800 So if 30 00:01:57,100 --> 00:02:01,300 in file do so if this file does not exist. 31 00:02:01,300 --> 00:02:03,600 So this condition will become true. 32 00:02:03,720 --> 00:02:08,620 You can do so you can write C out file does not exist. 33 00:02:12,960 --> 00:02:16,350 So this in file is actually a true false value. 34 00:02:16,410 --> 00:02:20,470 So if the file does not exist then you can print the file does not exist. 35 00:02:20,470 --> 00:02:22,090 So you can check also. 36 00:02:22,110 --> 00:02:25,530 Now there is one more function to check first is using this method. 37 00:02:25,530 --> 00:02:29,940 And second is basically you have a function is open so you can write it like this. 38 00:02:29,970 --> 00:02:30,300 If 39 00:02:34,440 --> 00:02:37,080 in file Dart is open. 40 00:02:37,080 --> 00:02:40,220 So this is a function is open it will return true. 41 00:02:40,320 --> 00:02:42,360 It will identical in value true or false. 42 00:02:42,390 --> 00:02:48,330 So if the file does not exist then you can write the same statement that file does not exist 43 00:02:51,590 --> 00:02:54,650 so you can use this way to check whether file exists or not. 44 00:02:54,650 --> 00:03:01,190 Or you can use this way to check whether my file exists or not Now what I want to do. 45 00:03:01,220 --> 00:03:04,090 So I want to read this file. 46 00:03:04,270 --> 00:03:05,230 So what is the format. 47 00:03:05,230 --> 00:03:08,470 So first of all you should know the format in which order the data is updating. 48 00:03:08,470 --> 00:03:09,810 So first is a string. 49 00:03:09,820 --> 00:03:11,380 Second is actually integer. 50 00:03:11,980 --> 00:03:13,410 So what do we do. 51 00:03:13,600 --> 00:03:14,700 First thing is a string. 52 00:03:14,710 --> 00:03:20,050 So you will create a variable string SDR for storing Hallowell and then you will create an in danger 53 00:03:20,080 --> 00:03:22,560 to store the digital value faith. 54 00:03:22,750 --> 00:03:23,010 Okay. 55 00:03:23,020 --> 00:03:28,930 So one important thing here is basically you should know the format the order in which the data is appearing 56 00:03:28,960 --> 00:03:31,570 in your text file. 57 00:03:31,660 --> 00:03:33,080 So what do you do. 58 00:03:33,220 --> 00:03:38,080 So you will use this object for example in file 2 I'm using in value or you can use in file. 59 00:03:38,110 --> 00:03:39,490 You can use any one of them. 60 00:03:39,940 --> 00:03:44,440 So for example if I'm using in file so I will write it like this in file 61 00:03:47,170 --> 00:03:47,750 SDR. 62 00:03:47,810 --> 00:03:54,200 Similarly in file I now after this what you can do. 63 00:03:54,200 --> 00:03:56,780 So after this you can print your data. 64 00:03:56,810 --> 00:04:00,460 So see out SDR and line. 65 00:04:00,470 --> 00:04:03,740 And similarly you can print your digital value which is five 66 00:04:08,580 --> 00:04:10,220 now after adding the compute data. 67 00:04:10,290 --> 00:04:11,700 I would reach and of the file. 68 00:04:11,730 --> 00:04:13,650 So this is end of file. 69 00:04:13,650 --> 00:04:18,090 Now I've a function and a file to check whether you reach an end of the file or not. 70 00:04:18,090 --> 00:04:20,080 So basically you can use this function. 71 00:04:20,130 --> 00:04:25,490 So if in file you will call this function. 72 00:04:25,520 --> 00:04:28,280 End of file E or F.. 73 00:04:28,300 --> 00:04:32,860 Now this function will return true or a false value so this function will again a boolean value. 74 00:04:32,860 --> 00:04:37,260 So if it is returning true that means I have reached the end of the file so you can print a message 75 00:04:37,280 --> 00:04:45,090 like and a file reached now after doing all the work that you want to do with the file. 76 00:04:45,150 --> 00:04:48,360 The most important thing is basically you have to close the connection. 77 00:04:48,360 --> 00:04:50,720 So you have to call the function close. 78 00:04:51,030 --> 00:04:53,620 So I will call in file dot close. 79 00:04:53,640 --> 00:04:58,930 And similarly you can also call in file to dart close. 80 00:04:58,980 --> 00:05:01,920 So this is all about reading from a fine. 81 00:05:01,920 --> 00:05:04,100 Now one important thing here is basically. 82 00:05:04,170 --> 00:05:12,190 So there are two modes actually so you can use a us in and the second mode is basically us out. 83 00:05:13,190 --> 00:05:14,630 So us in mode. 84 00:05:14,630 --> 00:05:19,640 So this is actually for reading the data and I use out is actually for writing the data. 85 00:05:19,730 --> 00:05:21,530 So we call these flags. 86 00:05:21,530 --> 00:05:28,250 So these are called flags or you can call them modes but I am using input file stream so input files 87 00:05:28,250 --> 00:05:33,490 stream that means that automatically means that I want to use this when I want to basically read. 88 00:05:33,500 --> 00:05:36,590 So that's why you do not need to mention the flags. 89 00:05:36,630 --> 00:05:37,490 I'm repeating myself. 90 00:05:37,490 --> 00:05:41,740 There are actually two types of flag input and output. 91 00:05:41,750 --> 00:05:47,690 You want to read or you want to write but since I'm using input file stream then it is obvious that 92 00:05:47,720 --> 00:05:49,210 I want to perform the operation. 93 00:05:49,220 --> 00:05:53,260 So that's why you do not need to mention these flags any of these flags. 94 00:05:53,300 --> 00:05:58,780 So in the next trade deal we will write the code I will see on the next one but I.