1 00:00:08,100 --> 00:00:13,970 A guys this is Caleb with Dev slopes and in this video we're going to download images using a new function 2 00:00:13,970 --> 00:00:15,470 called retrieve images. 3 00:00:15,500 --> 00:00:20,210 We're also going to write a little function called cancel all sessions that's going to allow us to cancel 4 00:00:20,210 --> 00:00:25,650 the download session so that we don't end up having a lot of duplicate sessions. 5 00:00:25,760 --> 00:00:30,150 And so that we can properly terminate them when they need to be terminated terminated. 6 00:00:30,150 --> 00:00:31,760 Anyway let's move on. 7 00:00:31,790 --> 00:00:36,980 So we're going to open our X code project here and we're going to start by writing a function called 8 00:00:37,040 --> 00:00:38,870 retrieve images. 9 00:00:38,900 --> 00:00:43,340 So go ahead and type that phunk retrieve images. 10 00:00:43,640 --> 00:00:47,230 And the cool thing is that this function whip's retrieve images. 11 00:00:47,450 --> 00:00:52,400 This function is going to be much easier to parse through the data because we've already downloaded 12 00:00:52,400 --> 00:00:55,940 it and appended it to the image you are LRA. 13 00:00:55,940 --> 00:00:59,660 So we're just dealing with a local array of you or else all these images. 14 00:00:59,660 --> 00:01:03,190 So it's going to be much easier to use the data. 15 00:01:03,260 --> 00:01:04,180 Pretty cool. 16 00:01:04,190 --> 00:01:10,460 So let's go ahead and we need to basically create a completion handler because we need to be able to 17 00:01:10,460 --> 00:01:16,310 notify that we have downloaded all of the images and get a notice that it's done so that we can reload 18 00:01:16,310 --> 00:01:20,090 the collection view load in all the images to the cells et cetera et cetera. 19 00:01:20,120 --> 00:01:28,160 So to do that we're going to basically create an identical handler to appear by typing handler at escaping 20 00:01:29,150 --> 00:01:34,490 or making it escaping so that the value can be passed outside of this function. 21 00:01:34,640 --> 00:01:36,750 Ok so it doesn't get stuck in the closure. 22 00:01:36,950 --> 00:01:42,020 And let's go ahead and create a function that's going to return an empty function we don't really need 23 00:01:42,020 --> 00:01:45,730 to return anything and that's why we're doing that inside the function. 24 00:01:45,740 --> 00:01:49,770 We use an underscore because function types are not allowed to have names. 25 00:01:49,850 --> 00:01:51,220 So we use an underscore. 26 00:01:51,470 --> 00:01:58,040 And we're just going to use this call this the status of type Boolean in case status means finished 27 00:01:58,040 --> 00:02:00,120 or not call. 28 00:02:00,170 --> 00:02:01,460 So that's that. 29 00:02:01,490 --> 00:02:07,580 Now we need to actually first create an array that's going to hold all the images just like we did with 30 00:02:07,580 --> 00:02:09,120 image you are right. 31 00:02:09,140 --> 00:02:15,530 So let's go up to the top of our class here and let's create a variable for that as well called var 32 00:02:15,860 --> 00:02:17,700 image array. 33 00:02:18,230 --> 00:02:27,830 And let's go ahead and call that type UI image OK and let's instantiate it. 34 00:02:27,830 --> 00:02:29,840 Scroll back down. 35 00:02:29,960 --> 00:02:31,080 And where were we. 36 00:02:31,130 --> 00:02:33,300 We were right here retrieve images. 37 00:02:33,320 --> 00:02:34,200 OK. 38 00:02:34,220 --> 00:02:37,880 When we enter this function we should first clear out image array. 39 00:02:37,880 --> 00:02:43,490 So go ahead and type image array and then equals empty brackets that way if there are currently images 40 00:02:43,490 --> 00:02:47,190 in there it's cleared out so that the new ones can come in and not interrupt. 41 00:02:47,480 --> 00:02:53,000 But basically what we're going to do now is we're going to cycle through our recently filled image you 42 00:02:53,000 --> 00:03:00,050 r l array and we're going to basically create an Alamo file request to download each image from its 43 00:03:00,050 --> 00:03:00,890 you are out. 44 00:03:01,010 --> 00:03:06,380 So go ahead and type for you Arel an image u r l array. 45 00:03:06,380 --> 00:03:14,340 Then we're going to call Alamo fire request and we'll pass it in the U R L K from our array. 46 00:03:14,360 --> 00:03:16,760 Now this is where we're using Alamo fire image. 47 00:03:16,760 --> 00:03:18,090 This is the coolest thing. 48 00:03:18,110 --> 00:03:23,180 Normally Alamo fire does not have the capability to download a straight up image. 49 00:03:23,240 --> 00:03:28,340 It does have the ability to download data or we could parse through Jason and then cast that as data 50 00:03:28,370 --> 00:03:31,250 and then create a UI image pass in the data. 51 00:03:31,310 --> 00:03:32,320 All of that. 52 00:03:32,600 --> 00:03:40,950 But Alamo fire image allows us to call daat response image to see that dot response image and it returns 53 00:03:40,950 --> 00:03:43,280 a completion handler of type image. 54 00:03:43,280 --> 00:03:50,120 So press enter on that and we're going to call this response because that's the response is a data response 55 00:03:50,710 --> 00:03:52,820 of type image. 56 00:03:52,820 --> 00:03:59,060 Now what we can do inside this function is we're going to deal with the response and we're going to 57 00:03:59,240 --> 00:04:02,530 create a constant that holds the image value. 58 00:04:02,540 --> 00:04:10,640 So go ahead and type guard let image equals response that result value that might help if I spell response 59 00:04:10,640 --> 00:04:16,520 right response that result value and that pulls out the image value from the response. 60 00:04:16,520 --> 00:04:21,510 Now of course if we don't get anything else we want to just return. 61 00:04:21,560 --> 00:04:24,710 Meaning get out of this function so that we don't have a crash. 62 00:04:24,710 --> 00:04:27,390 That's a way we can be a safe coder. 63 00:04:27,410 --> 00:04:28,780 Now we need to use this image. 64 00:04:28,790 --> 00:04:32,220 So we're going to go ahead and for this particular you are. 65 00:04:32,250 --> 00:04:40,270 We're going to call a self image array append and we're going to give it the image from our response. 66 00:04:40,290 --> 00:04:46,580 Now if you go ahead and look at what this is you'll see that it's of type image. 67 00:04:46,800 --> 00:04:51,120 And if we go into image array it's of type UI image. 68 00:04:51,120 --> 00:04:57,690 Now the cool thing is when we pass it in image is a comparable type from Alamo fire that we can use 69 00:04:57,690 --> 00:05:01,020 as an image is really really cool that it lets us do that. 70 00:05:01,020 --> 00:05:08,160 So we just downloaded an image from our u r l we append it to our image array and now we need to update 71 00:05:08,190 --> 00:05:11,810 our progress label right to show that that image has been downloaded. 72 00:05:12,000 --> 00:05:20,400 So let's go ahead and type self up progress label dot text and that's going to equal blank out of 40 73 00:05:20,760 --> 00:05:23,810 images downloaded. 74 00:05:23,910 --> 00:05:31,280 Now if you remember we basically have a number that is being downloaded every time this comes through 75 00:05:31,290 --> 00:05:32,900 we want it to be updated. 76 00:05:32,910 --> 00:05:37,370 So what we can do is we can give it the number of items in the image array. 77 00:05:37,380 --> 00:05:40,420 So let's go ahead and do that by using string encapsulation. 78 00:05:40,560 --> 00:05:46,890 And let's just call a self image array count that way once we have one it will show up as one out of 79 00:05:46,890 --> 00:05:49,710 40 images downloaded then two then three than four. 80 00:05:49,890 --> 00:05:55,980 And that is how we're going to store that value so that we can see how many images have been downloaded. 81 00:05:55,980 --> 00:05:58,610 So the user has a clue of what's going on. 82 00:05:58,740 --> 00:06:00,030 That's really easy. 83 00:06:00,060 --> 00:06:06,810 Now what we're going to do beneath this is we're going to set up a check to see if the amount of images 84 00:06:07,080 --> 00:06:10,850 in our image array matches the amount of you or else we downloaded. 85 00:06:11,040 --> 00:06:17,850 So to do that what we're going to do is we're going to go ahead and type if self image array count is 86 00:06:17,940 --> 00:06:23,200 equal to self image you are LRA count. 87 00:06:23,850 --> 00:06:26,030 Then we're going to go ahead and use our handler. 88 00:06:26,040 --> 00:06:28,010 That's when we know that we're done. 89 00:06:28,170 --> 00:06:32,790 So type handler and pass it a boolean of true. 90 00:06:33,000 --> 00:06:34,570 That is how we know that we're done. 91 00:06:34,590 --> 00:06:38,200 And that's how we can tell that we have all of the images that we need. 92 00:06:38,490 --> 00:06:45,390 So let's go ahead and let's go up to where we called this originally which is in drop pin and we need 93 00:06:45,390 --> 00:06:46,850 to think what are we going to do now. 94 00:06:46,860 --> 00:06:49,120 We've retrieved all of our you ourselves. 95 00:06:49,260 --> 00:06:55,470 And we actually can get rid of this print function but now that we have retrieved them we need to retrieve 96 00:06:55,470 --> 00:06:57,130 all the images from them. 97 00:06:57,210 --> 00:06:58,540 But I see a problem. 98 00:06:58,650 --> 00:07:01,380 We passed in true here and that works. 99 00:07:01,380 --> 00:07:09,750 But the issue is that this is supposed to be a constant with its own unique name like finished K meaning 100 00:07:09,750 --> 00:07:15,690 that the value could be set as true or false but simply by passing in true here we're sort of overwriting 101 00:07:15,690 --> 00:07:17,130 this to always return true. 102 00:07:17,130 --> 00:07:18,360 But what if it failed. 103 00:07:18,420 --> 00:07:23,610 So we need to pass in finished so that we know whether or not we actually have a true or false value 104 00:07:23,620 --> 00:07:30,660 it should be able to change and we need to do a conditional check here so if finished meaning if finished 105 00:07:30,660 --> 00:07:33,550 returns as true we could also do if finished equals true. 106 00:07:33,570 --> 00:07:36,330 That's fine but you can just say if finished. 107 00:07:36,330 --> 00:07:41,950 Meaning if it's true then what we need to do is retrieve images. 108 00:07:42,000 --> 00:07:43,540 Simple as that. 109 00:07:43,620 --> 00:07:48,620 And of course we we're going to want to use the handler so that we know when that is finished. 110 00:07:48,930 --> 00:07:50,250 And let's go ahead and type that. 111 00:07:50,250 --> 00:07:53,480 So finished is what we can use for that handler. 112 00:07:53,490 --> 00:07:56,570 That's how we know that we're done downloading all of our images. 113 00:07:56,820 --> 00:08:03,180 And what do we want to do if finished what should we do. 114 00:08:03,180 --> 00:08:09,660 Well we should hide the spinner because remember the spinner is spinning on our collection. 115 00:08:09,960 --> 00:08:17,160 We should hide the label and we should also reload our collection view with all of the images that we 116 00:08:17,160 --> 00:08:18,030 just now download. 117 00:08:18,060 --> 00:08:21,930 We want them to show up right so we can do two of these things. 118 00:08:21,930 --> 00:08:25,060 Now we can hide the spinner and we can hide the label. 119 00:08:25,080 --> 00:08:33,660 So I'm going to delete those and call self dot remove spinner and self remove label or remove progress 120 00:08:33,660 --> 00:08:34,790 label rather. 121 00:08:34,830 --> 00:08:37,410 And those are the two things that we can do. 122 00:08:37,410 --> 00:08:42,690 We have not yet set up our collection view to even pull data from our image array. 123 00:08:42,810 --> 00:08:44,090 We'll do that in the next video. 124 00:08:44,250 --> 00:08:47,860 But I'm going to save this here so that we remember that that's what we're going to do. 125 00:08:47,880 --> 00:08:51,340 There's only one last issue we need to look at and that is here. 126 00:08:51,420 --> 00:08:57,090 Since we're inside of another closure we need to call self because this dysfunction is publicly accessible 127 00:08:58,320 --> 00:09:02,610 in this class and we need to call self so that we can use it from the view controller. 128 00:09:02,650 --> 00:09:08,230 So we should go ahead and check to see if this works we should get all of our images downloading. 129 00:09:08,480 --> 00:09:12,950 It should update our label it should remove our spinner and progress label when it reaches 40. 130 00:09:12,950 --> 00:09:14,510 Let's go ahead and build and run. 131 00:09:14,660 --> 00:09:15,980 Let's see how we did. 132 00:09:16,040 --> 00:09:21,020 And then in the next video we'll set up our collection view so that it actually loads the images into 133 00:09:21,050 --> 00:09:23,350 all of the different cells in the collection view. 134 00:09:23,660 --> 00:09:26,280 So let's give it a try. 135 00:09:26,320 --> 00:09:35,820 It's loading K There we go we have zoomed in let's drop a pin and let's see if the label gets updated. 136 00:09:40,470 --> 00:09:40,880 All right. 137 00:09:40,890 --> 00:09:41,550 Awesome. 138 00:09:41,550 --> 00:09:45,510 So it looks like the label is showing up it says three out of 45 out of 46 out of 40. 139 00:09:45,510 --> 00:09:45,950 OK good. 140 00:09:45,950 --> 00:09:50,880 So it's updating every time there's a photo downloading and I'm noticing that the fonts too big. 141 00:09:50,880 --> 00:09:55,320 So I'm actually going to go change that where we create the label which I think is up here near the 142 00:09:55,320 --> 00:09:58,890 top add progress label. 143 00:09:59,040 --> 00:10:00,880 Let's make it maybe size 14. 144 00:10:00,900 --> 00:10:02,870 That'll update in the next build. 145 00:10:02,880 --> 00:10:06,980 So for now we're just waiting until it gets to 40 to see if it properly hides. 146 00:10:06,990 --> 00:10:11,350 And later it will reload the collection view. 147 00:10:11,490 --> 00:10:12,000 All right. 148 00:10:12,120 --> 00:10:12,490 Awesome. 149 00:10:12,480 --> 00:10:14,450 So it looks like it made it to 40. 150 00:10:14,490 --> 00:10:15,630 It hid. 151 00:10:15,840 --> 00:10:18,170 And that's exactly what we were hoping for. 152 00:10:18,170 --> 00:10:19,020 This is awesome. 153 00:10:19,020 --> 00:10:27,060 So now we need to handle the instance of what if a user cancels What if they swipe down like we can 154 00:10:27,270 --> 00:10:30,750 to cancel it should stop the request it should stop the download. 155 00:10:30,750 --> 00:10:31,640 Right. 156 00:10:31,740 --> 00:10:35,770 And we're going to set up a function that can do that called cancel all sessions. 157 00:10:35,970 --> 00:10:41,480 So in order to get to that scroll down and we're going to put it right beneath retrieve images. 158 00:10:41,480 --> 00:10:50,280 Go ahead and type phunk cancel all sessions and then inside of those curly braces we're going to actually 159 00:10:50,310 --> 00:10:53,450 access a singleton class from Alamo fire. 160 00:10:53,460 --> 00:10:58,560 So go ahead and type Alom a fire session manager that's a singleton. 161 00:10:58,560 --> 00:11:01,380 We're going to get the default session manager. 162 00:11:01,380 --> 00:11:07,080 We're going to get it session and we're going to call a function here called Get tasks with completion 163 00:11:07,080 --> 00:11:08,370 handler. 164 00:11:08,490 --> 00:11:15,700 Now press enter to set up this completion handler and we're going to call this session data task. 165 00:11:15,920 --> 00:11:19,110 Ok this is all of the data tasks that come in. 166 00:11:19,110 --> 00:11:23,900 This is going to be called upload up load data. 167 00:11:24,090 --> 00:11:24,520 OK. 168 00:11:24,570 --> 00:11:26,880 And this is going to be download data. 169 00:11:26,880 --> 00:11:34,440 These are three constants that are used to hold all three different types of sessions that can be happening 170 00:11:34,470 --> 00:11:35,210 in your app. 171 00:11:35,370 --> 00:11:40,770 Now we're required to use all three of these here but we are not required to use them all within the 172 00:11:40,770 --> 00:11:41,520 closure. 173 00:11:41,550 --> 00:11:42,630 We're not uploading anything. 174 00:11:42,630 --> 00:11:46,020 So we actually don't need to worry about the upload data session task. 175 00:11:46,020 --> 00:11:47,520 But here's what we're going to do. 176 00:11:47,520 --> 00:11:53,160 We're going to cancel every instance of session data task and every instance of download data. 177 00:11:53,370 --> 00:11:56,520 If you look you can see that session data task. 178 00:11:56,760 --> 00:12:00,960 Maybe you can't at the moment well anyway session data task is an array. 179 00:12:00,960 --> 00:12:01,590 This is an array. 180 00:12:01,590 --> 00:12:06,300 This is an array we have arrays here meaning we're going to need to cycle through all of them to cancel 181 00:12:06,300 --> 00:12:07,500 all the tasks. 182 00:12:07,500 --> 00:12:10,630 There's a really cool and easy Swiftie way to do it. 183 00:12:10,650 --> 00:12:18,390 So let's start with the session data task by typing session data task for each and for each allows us 184 00:12:18,390 --> 00:12:24,180 basically to cycle through like a for loop but instead of saying for a task in-session data task and 185 00:12:24,180 --> 00:12:31,200 then calling tasks cancel what we can do is instead we can give it some curly braces we can use dollar 186 00:12:31,200 --> 00:12:38,640 signs zero and dollar signs zero basically creates that placeholder as if we were typing for a task 187 00:12:38,700 --> 00:12:41,600 in session data task right. 188 00:12:41,610 --> 00:12:45,220 We could do a print task or will like. 189 00:12:45,230 --> 00:12:53,160 Like I said we could do tasks cancel right now task is like a temporary variable that is used for every 190 00:12:53,160 --> 00:12:55,150 instance in that array. 191 00:12:55,350 --> 00:13:00,400 Dollar Signs zero is the same thing it's just kind of a generic variable name. 192 00:13:00,600 --> 00:13:04,500 And so we can just call DOT cancel we can fit everything on one line. 193 00:13:04,500 --> 00:13:05,850 It's like a single line for loop. 194 00:13:05,850 --> 00:13:07,170 Really really cool. 195 00:13:07,170 --> 00:13:11,880 So we just canceled all of the session data tasks and now we need to cancel all of the download data 196 00:13:11,880 --> 00:13:18,340 tasks as well so called download data for each wups for each make sure you get the right one there. 197 00:13:18,540 --> 00:13:20,880 Curly braces and then inside. 198 00:13:21,030 --> 00:13:24,310 Dollar Signs zero dot cancel. 199 00:13:24,540 --> 00:13:29,040 Now using this function we just canceled all of the sessions that we need. 200 00:13:29,040 --> 00:13:35,130 And that's actually the perfect way to make sure that you're not having multiple data sessions happening 201 00:13:35,130 --> 00:13:40,230 on top of one another that can be really really inefficient in your app and so we're going to make sure 202 00:13:40,230 --> 00:13:42,360 that our app is nice and efficient. 203 00:13:42,360 --> 00:13:44,850 And now we need to just think of where does this go. 204 00:13:44,850 --> 00:13:46,860 Cancel all sessions. 205 00:13:46,860 --> 00:13:54,260 Remember in our app when we drop a pen it pulls up our view here like that when we swipe down. 206 00:13:54,330 --> 00:13:55,280 It hides. 207 00:13:55,470 --> 00:13:59,100 I think that's where it should be cancelling every session as well. 208 00:13:59,100 --> 00:14:03,870 So we need to go find the animate down function which I believe is up here. 209 00:14:04,170 --> 00:14:04,680 Yes. 210 00:14:04,740 --> 00:14:05,210 OK. 211 00:14:05,430 --> 00:14:10,470 So animate view down is here and whenever we swipe down we should cancel all sessions. 212 00:14:10,470 --> 00:14:13,010 That's a great place to put it. 213 00:14:13,080 --> 00:14:14,520 So that's looking good. 214 00:14:14,530 --> 00:14:16,360 That'll cancel all of the sessions. 215 00:14:16,410 --> 00:14:23,640 Now there's another thing that we should do is well what if the view is up and what if we click to add 216 00:14:23,700 --> 00:14:24,300 a new pin. 217 00:14:24,300 --> 00:14:29,640 Right let's say we get to maybe 4 photos and we add a new pin. 218 00:14:29,670 --> 00:14:34,460 Believe it or not it's not actually canceling the session it's creating a new one on top of that. 219 00:14:34,470 --> 00:14:39,810 So in order to be the most efficient we should definitely remove or cancel all sessions before we start 220 00:14:39,810 --> 00:14:40,870 a new session. 221 00:14:40,920 --> 00:14:47,280 So in droppin that's that's where we double click and drop a pin we should cancel the session and started 222 00:14:47,280 --> 00:14:51,730 over so that we get a brand new fresh fresh session every time. 223 00:14:51,750 --> 00:14:52,430 Very cool. 224 00:14:52,440 --> 00:14:57,840 So let's go ahead and call cancel all sessions from drop in as well when we remove all of the stuff 225 00:14:57,840 --> 00:15:00,490 we might as well remove the session as well. 226 00:15:00,660 --> 00:15:02,940 So very very cool. 227 00:15:03,060 --> 00:15:07,720 Well sorry let's actually go check to see if this works let's build and run it before we move on. 228 00:15:08,220 --> 00:15:14,260 We'll have the the terminal or the console pop up and the console will show us when the sessions are 229 00:15:14,320 --> 00:15:14,880 exited. 230 00:15:14,950 --> 00:15:21,500 So let's go ahead and open it up here we'll get a lot of a lot of debug messages here. 231 00:15:21,550 --> 00:15:26,410 Now I'm going to go ahead and drop a new pin cancelled out and you'll see right here it says finished 232 00:15:26,410 --> 00:15:32,440 with error and error just means that it printed an error saying maybe user cancelled session or something 233 00:15:32,440 --> 00:15:33,700 like that. 234 00:15:33,970 --> 00:15:40,960 But the cool thing is if I swipe down as well like so you'll notice we get the same finished with error 235 00:15:40,960 --> 00:15:43,930 message meaning the task is being canceled and we're starting over. 236 00:15:43,930 --> 00:15:44,900 Every single time. 237 00:15:45,130 --> 00:15:46,590 Which is really really cool. 238 00:15:46,600 --> 00:15:51,650 This is a great way to make sure that our app is nice and efficient and not wasting any resources. 239 00:15:51,690 --> 00:15:55,250 So go ahead and we're going to move on to the next video. 240 00:15:55,360 --> 00:16:00,910 We're going to set up our collection view to have an image view to pass in an image to that image view 241 00:16:01,120 --> 00:16:04,150 and to add that is a sub view to our collection view cell. 242 00:16:04,150 --> 00:16:07,680 That way we can show all of our awesome images that we just downloaded from Flickr. 243 00:16:07,680 --> 00:16:10,060 I'm really excited to get that working. 244 00:16:10,060 --> 00:16:13,080 So let's go ahead and head over to the next video and let's get it set up.