WEBVTT 00:06.370 --> 00:11.870 In this video you're going to learn how to create arrays from other objects in E6. 00:11.920 --> 00:19.150 So in iOS 6 you can create an array from objects which are similar to arrays like strings collections 00:19.180 --> 00:20.530 and so on. 00:20.530 --> 00:27.430 So these objects they are simulated arrays because they have a length property and they may also have 00:27.580 --> 00:30.280 elements indexing or they may not. 00:30.280 --> 00:31.040 All right. 00:31.240 --> 00:37.360 So first let's understand why you would need to create arrays from such objects. 00:37.360 --> 00:42.700 And then after that you're going to have a few examples where we can create arrays from collections 00:42.760 --> 00:45.550 strings functions and so on. 00:45.550 --> 00:50.940 So you're going to have a few essential elements which you're gonna use later. 00:51.010 --> 00:55.870 So you've got you've got a few divs here with a class Blue which you're going to use at some point to 00:55.870 --> 00:57.430 create a collection. 00:57.430 --> 01:05.520 So for now let's understand why we need to create arrays from other objects so let's create an array. 01:05.550 --> 01:06.070 Distance 01:12.010 --> 01:20.680 and let's explore some of the methods of the Array objects that you wouldn't find in a collection or 01:20.680 --> 01:22.360 a string for example. 01:22.390 --> 01:24.990 So a good example of that is the map function. 01:25.630 --> 01:31.650 So you can create a new array out of this array using the map function. 01:31.690 --> 01:38.580 And if I remember you pass a function to the map function or the map method. 01:38.670 --> 01:48.870 So let's say that we cannot pass a function that returns the or X multiplied by two. 01:48.870 --> 01:50.830 And now you get to 4 and 6. 01:50.830 --> 01:57.730 So we took that array we used the map method and we applied this function to the elements of the array 01:58.120 --> 02:01.410 and we created a new array. 02:01.420 --> 02:11.780 Now if you Troy the map method with a string for example unfortunately it is not gonna work. 02:11.830 --> 02:24.550 So if you log X dots map you get undefined meaning that map is not attached to a string but if you log 02:25.960 --> 02:32.660 the array dots map you'll get a function because the function does exists for an array. 02:33.460 --> 02:41.230 So to use the map method with a string in year five we had to do some really laborious work we had to 02:41.230 --> 02:52.900 go back through the array prototype like this array dot prototype and then we used the map method like 02:52.900 --> 02:58.570 that's why using the call function. 02:58.570 --> 03:05.960 So this function takes are they first parameter the value you want for this which is gonna be your string. 03:06.230 --> 03:06.860 All right. 03:06.860 --> 03:11.690 And so let's call this drink you are just to avoid any confusion 03:16.420 --> 03:22.690 and then you specify the arguments of your map method. 03:22.780 --> 03:25.090 So let's say that we want a function 03:28.590 --> 03:30.690 okay so I'm not gonna use an error function. 03:30.690 --> 03:34.090 I'm gonna use a simple function here because we said back to iOS 5. 03:34.570 --> 03:39.690 So while you can still use a narrow function that's absolutely fine. 03:39.970 --> 03:43.420 I'm gonna go for this syntax for now the S5 seems likes. 03:43.640 --> 03:57.720 So let's say that s the function takes a parameter X and returns x plus a for example all right. 03:57.790 --> 04:00.220 And now you get a new string. 04:01.740 --> 04:04.380 So that's really laborious. 04:04.380 --> 04:05.020 All right. 04:05.070 --> 04:12.630 So in E6 instead of writing all that code you can just convert the string to an array and then use the 04:12.690 --> 04:14.440 map method if you like. 04:14.580 --> 04:14.850 All right. 04:15.180 --> 04:28.090 So to convert an array to a string you just use the from method of the array object to which you parse 04:28.240 --> 04:30.010 the string. 04:30.010 --> 04:37.420 So now if you do that you're gonna get a new array created from this string. 04:37.420 --> 04:42.970 So now you can use all sorts of methods which are attached to the array prototype so you can use the 04:43.000 --> 04:47.490 mop method you can use the sliced method and so on. 04:47.720 --> 04:48.230 Right. 04:48.430 --> 05:00.230 So let's go back now two years five and understand why we we still need the to create arrays from other 05:00.390 --> 05:02.270 these are types like collections. 05:02.960 --> 05:10.060 So here we've got three lives of class blue. 05:10.190 --> 05:14.340 So what we're gonna do we can create a 05:18.610 --> 05:28.770 collection of these elements by selecting all elements of class blue so you can use a concept here instead 05:28.780 --> 05:36.870 of let's not really because we changed array afterwards. 05:36.920 --> 05:37.890 That's fine as well. 05:37.970 --> 05:51.170 So in our collection we're gonna have all the elements of class blue. 05:51.670 --> 05:58.670 So if your log collection you get in a shameful collection. 05:59.080 --> 06:06.970 So now let's say that you want to get only one portion of the collection. 06:07.390 --> 06:16.330 For example only the elements of index one of the elements of index to know if you had an array you 06:16.330 --> 06:18.630 could do thus using the slice method. 06:19.030 --> 06:25.810 But the slice method doesn't work with a collection to be try that you get undefined. 06:25.810 --> 06:29.410 There is no slice method attached to a collection. 06:29.410 --> 06:34.150 So again to do that in year five 06:38.240 --> 06:44.760 you had to use the slice method attached to the array prototype. 06:46.380 --> 06:46.630 Okay 06:51.790 --> 06:52.300 like this 06:55.230 --> 07:00.640 and then you had to use the call method specify the value of this which is gonna be your collection 07:01.840 --> 07:04.930 and then you parse the arguments of these slice function here. 07:04.930 --> 07:09.590 So we want to go from the elements of indexed one to the elements of index 2. 07:09.700 --> 07:15.190 So that's going to be from 1 to 3. 07:15.190 --> 07:15.440 All right. 07:15.460 --> 07:23.450 Because this will go from the elements 1 until 3 3 not included. 07:23.670 --> 07:23.890 All right. 07:23.890 --> 07:25.140 So now if we try these 07:28.640 --> 07:37.860 you will get an array this time and you get only the first or the elements of index 1 and the element 07:37.860 --> 07:39.270 of index 2. 07:39.540 --> 07:47.070 Now in iOS 6 you can convert the collection to an array and then use this like method. 07:47.190 --> 07:47.820 All right. 07:47.910 --> 07:51.840 So to to convert the collection. 07:51.840 --> 07:59.400 So you just use the array objects from method and you pass the collection so it's like that. 07:59.440 --> 08:01.540 And this time you get an array. 08:01.590 --> 08:09.070 Now you can use the slice method as you like attach it to this element. 08:09.220 --> 08:09.500 All right. 08:09.500 --> 08:17.100 So this explains why you would need to create arrays from other objects which are similar to arrays. 08:17.110 --> 08:23.010 Now let's have a look at one more example creating an array from function arguments so it creates a 08:23.010 --> 08:30.470 function G which takes a couple of promises. 08:30.620 --> 08:33.470 So first let's log the arguments 08:38.910 --> 08:42.220 so let's call g of 1 and 2. 08:42.220 --> 08:49.060 So the arguments and arguments elements it's not really in the right and you can see all elements inside 08:49.060 --> 08:49.820 the arguments. 08:49.880 --> 08:53.110 You can see your parameters and so on. 08:53.530 --> 08:54.510 All right. 08:54.580 --> 09:04.510 So now if you want to convert the arguments to the right again you use great dots from 09:10.050 --> 09:17.040 right and you've got an array and now you can use all sorts of methods which attach to the array prototype. 09:17.150 --> 09:17.430 All right. 09:17.430 --> 09:22.950 So in the next video you're going to learn some other features of the array dots from method.