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in the last video we started tidying up

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our download XML function to write it

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more how you do it in Kotlin rather than

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converted Java now that was a useful

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exercise and seeing things like the

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catch blocks being changed will help you

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to write better Kotlin code now the

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catch block change didn't save us a lot

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of code but when we replaced our while

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loop with a single line in Kotlin well

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that saved quite a bit of code

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now unless code means fewer errors so

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that's definitely an improvement so as

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promised i'm now going to replace the

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download XML function with just one line

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of Kotlin so the first thing to do is to

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deal to delete all the code we've got in

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here in there I'm going to delete

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everything out of the download XML

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function look so now at the moment we're

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getting an error because the function is

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not returning anything so we better tell

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it what to return so let's do return URL

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URL path dot retakes and that's it let's

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make sure it works before we look at

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what's actually going on you can see the

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code is just literally one line so let's

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start bring up the logcat we'll clear it

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and we'll actually run it and then if

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you need to see the emulator screen we

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just need to see the log count output

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and you can see that everything's worked

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as it's done before we're still seeing

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the XML downloaded code and the various

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uncreate doing background so on and so

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forth that's all working so basically

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the oncreate starting and finishing just

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like before then the background task

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executes with the URL that we provided

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now there's no logging for download XML

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because there's nothing really to log it

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obviously works though because we get

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we're getting the XML logged by the on

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post execute function now I will say

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that there was nothing wrong with our

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previous code and you'll see in a moment

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why you might need to use code like that

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so the steps we went through in the last

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video were important I didn't just get

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you to type in all that code just so you

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can see how impressive this is although

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I will say it is pretty impressive but

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let's actually have a look at what's

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going on

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how Commons let us replace all that code

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with just a single line now Cullen

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provides something called extension

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functions which are a great way to add

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extra functions to existing classes

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now here the Kotlin library's added read

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text as an extension function to the URL

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class no URL is a class from the

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standard Java library in the package

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java.net now you can check that by

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holding down ctrl or command on URL and

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hovering over URL as I'm doing there now

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I won't click on it because I don't yet

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have the API 26 source code but the

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tooltip tells us all we need to know and

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you can see where it's coming from

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Java declarations java.net so URL is a

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Java class that's been around for a long

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time now the colon developers wanted to

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give it a read text method but they

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can't go messing about with standard

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Java libraries

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so instead Kotlin allows extension

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functions to be attached to existing

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classes and call us so they really

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belong to that class so that's what read

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text is an extension function now we can

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have a look at it by ctrl or command

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clicking read text let's do that this

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takes us to the Kotlin readwrite module

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where Kotlin added all sorts of

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functions to standard Java classes in

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fact we've been here before because if

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you scroll a short way up we should be

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able to see the reader dot read text

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there's reader copy to and reader dot

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read text we looked at those earlier

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alright so back down to what URL don't

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read text

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and the docstring there says reads the

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entire content of this URL as a string

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and that's just what our previous code

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was doing we just did it the long way so

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read text is a function that returns a

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string so it works by calling the read

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bytes function then returning the result

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of Dennis a string by calling the two

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string function now read bytes appears

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at the end of the file

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you can see that and then read bots it

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calls open stream and uses that to read

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bytes from it now this is very similar

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to what we've seen so you probably won't

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be surprised by what we see when I

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control click on it or command or

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control click read bytes we're gonna

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come over here the oit don't read bias

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and click on read bytes over there we've

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been here as well so her read bytes uses

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that copy to function to read from the

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stream and copy to use as a while loop

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there it is just above

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as you can see on the screen there at

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the top that's just above the read bytes

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extension function now before we go back

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to our e-text in the readwrite Kotlin

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code notice are covered that it is the

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caller's responsibility to close this

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dream now this may worry you but it

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needn't so if we close our iOS dreams

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Katie now and we're back at readwrite

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Katie the use function actually takes

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care of closing down the resources as we

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saw earlier so that's handled for us now

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the last thing that I want to mention

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here is that the second line for the doc

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string for read text this method is not

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recommended on huge files now that's why

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our previous code may be useful so

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getting it all working and Kotlin wasn't

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a wasted exercise you know if you're

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dealing with a lot of data it's

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important to remember that read text

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will read the whole lot into a string in

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memory

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now what's meant by huge depends on the

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environment you might think nothing of

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reading a gigabyte on a desktop computer

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with 32 gigabytes of RAM but we're

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writing apps for Android devices though

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so even a couple of megabytes can be

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considered huge now the Downloads that

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we'll be dealing with for this feat are

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just a few kilobytes but if you

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experiment with different feeds

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definitely keep an eye on their size now

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as you browse through these Kotlin

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libraries to get a feel for what's

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provided make sure you also pay

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attention to any comments like this one

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Kotlin can make coding a lot easier but

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it's up to you to only use features when

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they are appropriate with great power

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comes great responsibility

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now before I finish I'm going to check

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the import section of main activity and

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it claims down read/write cought at the

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moment the Kotlin plugin isn't very good

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at removing unused import so we may

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still have the Java net and Java dot IO

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imports for the code we deleted now in

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my case I haven't because I've optimized

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imports to be automatically updated or

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the unused imports will be removed

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automatically but if you've got any

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unused imports here now there would be a

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good time to get rid of them and what

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you should end up is a little green dot

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will end up with is a little green tick

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in the right-hand corner we need to when

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you're when you're saying that you know

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that you're ready to continue all right

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so let's finish the video here and in

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the next one we're gonna make a start on

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passing out the information we want

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from the XML that we've downloaded see

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you in the next video