Flutter 16 - Intro to Libraries Video Lecture | Flutter: Build beautiful native apps in record time - App Development

hey everybody it's Brian and welcome to
the 16th flutter tutorial we're still on
the dart learning curve here we've
covered quite a bit but what we need to
do now is we scroll all the way down
here you can see there's libraries and
visibility and I wanted to talk about
this a little bit here in dart
everything is a library including the
programs that we've made up to this
point there's a distinction in how those
libraries are actually set up and how
they're used though another distinction
is whether they're internal to Dart
they start with the import dart
semicolon or whether they are packages
that are not included in dart itself
there is a lot out there and to be
brutally honest there's some of these
features you may never actually use you
can import a package as a variable you
can actually show only specific parts of
the package and hide specific parts of a
package you can even do lazy loading of
a library meaning you can have this
massive library and only load the pieces
you need as you need them it's actually
a really cool feature
they don't really cover it a lot in the
tour of dart you have to actually click
on libraries over here and you can see
there's a tour of the dart libraries
commonly used libraries and then a whole
tutorial on how to create your own
library packages we're going to cover a
little bit of this but I wanted you to
be aware of this for future tutorials
here that when you click on that let me
back up in case that wasn't apparent
what I did you click on tour of dart
libraries and you can see they have got
just a ton of information of all of the
built-in functionality with dart and
their slogan is batteries included which
I think they kind of took that and
plagiarized that from Python I'm not
sure which one came first I'm pretty
sure was Python but anyways it is
actually batteries included there's a
lot of bang for your buck in here one of
my favorites is they have you know
browser-based apps they have I oh they
have conversion and they have mirroring
which is reflection so it's really nice
to have this right into the library
itself so you don't have to go and get
something external however back here you
should be aware that you can actually
make your own and you can publish it out
on this thing called
pub.dartlang.org now if you're wondering
what it's pub pub is a tool for managing
directors and if you go out to pop dart
playing org you can see there is a lot
out here so let's say we want to and I'm
just going to pick something at random
image you can see there's image pictures
flutter image syllable image image
carousels image transformers okay let's
try something little more specific like
resize alright so here's a good one
provides a server and web apps with the
ability to load manipulate save him just
various image file formats and you can
see it works in flutter it works on
server and it works on web so we
actually just click on this and it gives
you a brief rundown and not all of these
are created equally mind you but some of
them have a lot of documentation some of
them don't you can see the author this
was not an official dart package and you
can see that has no reliant reliance on
dart io so it can be used on both server
and web applications you can read right
all of these formats read only those and
it has all of these functions built in
and it has changelog and how to install
and how to use which we'll cover in a
future tutorial but for this tutorial
specifically I wanted you to know that
that functionality exists just know that
there is a massive amount and it's
growing daily of libraries out there for
you to use and just about any
functionality you can think of already
out there and it's I mean as you're
listening to me speak it is continuing
to grow and grow and grow I've heard a
lot of programmers say oh darn tis dead
don't work with dart I've actually seen
it grow right before my own eyes and
it's kind of crazy
so let's dive into you this one we're
gonna make our console and we'll call
this lib intro why I don't know just
because I couldn't come up with a better
name alright so now that we have got
this a little bit of explaining what's
going on here you can see how we have
this folder live we have this folder pub
when we use something out on the public
ie in pub dart it actually goes in here
and you'll see that in future tutorials
what we're going to be working with is
right here and in the built-in libraries
so let's actually expand this and this
is just boilerplate this comes with
every single application that we've made
to date and you can see how it says
import package semicolon and then as the
path live intro slash live intro are as
because we're importing this as a
variable and then we can down here live
intro calc and we can import this it has
pretty much anything we want I mean we
could say cat and then it will calculate
using the function out here and we've
talked about it before how we can add
things in it's a pretty strong feature
to be able to do that you can structure
this pretty much any way you want there
are some caveats one thing you'll have
to have and we'll cover this one we
actually build our own library is you'll
have to have this pub spec Y amel which
just has some details into it all right
so what I wanted to cover is the
differences here
so let's actually work with a built in
dart package here so let's say local
notice how I'm starting with dart
semicolon and you can see all of these
that it come built-in that's pretty
crazy right we've worked with a sync
before so that's what we're going to
work with is called convert convert
really has some pretty nice features to
it but what we're going to work with a
little bit is called JSON if you don't
know what that is it's a way of
stringify I guess is a good way of
putting it an object so that you can
work with it some people like XML some
people like JSON it basically takes an
object and makes it into a giant string
or variable that you can pump off to the
network read it into another program and
convert it back into an object so we're
going to make a map and I'm going to say
string int and then we're going to say
map what if absent and what we're going
to do here is we're just going to say
put my age in here and now I feel old I
feel ancient
I play call of duty and these kids like
mop the map with my face hey we'll just
throw my daughter in there so what we're
gonna do now is we're going to actually
convert that object into a string so I'm
gonna say string in code and we're going
to encode the map itself and we're just
gonna print this out and you can see
there is the JSON right there that's the
string representation of that object so
now we want to convert this well from a
string back into an object so we're
gonna say map
string int and let's call this people so
we know that we have a different object
all together
and we're going to take that string and
decode that into an object and we're
just going to say people for each and
then we have our key value pair maybe
that was kind of bad we have our key
value pair
yeah we're just gonna print that out so
really all we're doing is we're taking
our map our object using JSON to encode
it into a string and then using JSON to
take that string and decode it back into
an object and you can see here's our
JSON and here's our actual decoded
object being printed out Li for each so
if this seems like a very simple example
but it really shows you just how
powerful dart is not so much that it can
do JSON encoding and decoding other
languages can do that obviously but the
fact that you can very easily add this
functionality right into your
application without jumping through a
lot of Hoops like you have to with other
languages sometimes you'll have to
import this do some local bill do some
extra steps do some configuration dot it
on most of the time it's very simple
very easy and I think in future
tutorials probably actually maybe the
next tutorial we're gonna actually show
how to just grab something random off of
pub dartlang.org and show you how to
leverage somebody else's code I may have
to actually well I mean I mean it's not
that I'm a I'm going to definitely have
to test a few of these that make sure
they actually work as intended but I
mean as you can see just about anything
you can really think I'm like let's just
say so you want to do a server
let's look out here ok so there's all
different types of TCP servers web
server there's a multi server web server
middleware ICU server let's just pick
something completely random here let's
say IRC there's an IRC library out here
IRC client I mean as you can see there's
just a lot out here and it's I hate to
sound like a broken record but it's
continually growing so it's very
important that you learn how to work
with this because a lot of the times
you'll find functionality that you need
already exists and rather than
reinventing the wheel you're going to
have to import the
and actually work with it that's all for
this tutorial I hope you found this
educational entertaining
once again visit my website void rom-com
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