text stringlengths 1 81 | start float64 0 10.1k | duration float64 0 24.9 |
|---|---|---|
But we never actually hook
that up for this example. | 1,655.43 | 4.53 |
So in the TODO component here
we're passing down an onToggle prop | 1,659.96 | 4.97 |
but we never actually use it up here. | 1,664.93 | 2.52 |
And so here we should actually
have the switch when we do on-- | 1,667.45 | 7.65 |
what's it called-- on value change. | 1,675.1 | 3.02 |
And I only know this because
that's what the documentation says. | 1,678.12 | 4.06 |
And so when that value changed,
I should run props.onToggle, | 1,682.18 | 6.18 |
which is the name of the
prop that we're passing down | 1,688.36 | 3.03 |
from this parent component. | 1,691.39 | 1.95 |
And so now when we
click TODO it updates. | 1,693.34 | 4.25 |
And as you see right here the unchecked
TODO count still updates as expected. | 1,697.59 | 5.664 |
And so now if we create a bunch
we can see those numbers changing. | 1,703.254 | 3.986 |
We can see the checking and
toggling works as expected. | 1,707.24 | 2.75 |
We see if we delete this
one the TODO count goes down | 1,709.99 | 2.43 |
but the uncheck count does not
go down since it was checked. | 1,712.42 | 2.704 |
If we delete something that isn't
checked, both of them go down. | 1,715.124 | 2.666 |
And so we have the same behavior as
we did in our React Web application. | 1,717.79 | 5.917 |
Any questions there? | 1,728.58 | 1.18 |
So we have this being a scroll view. | 1,735.2 | 2.73 |
But, if you notice, the
scroll view gets cut off early | 1,737.93 | 2.77 |
and as we add TODOs it grows. | 1,740.7 | 4.23 |
But if we add a bunch of
TODOs it grows with it. | 1,744.93 | 11.59 |
But say we actually wanted the scroll
view to reach all the way to the bottom | 1,756.52 | 6.54 |
no matter how many TODOs were there. | 1,763.06 | 2.25 |
Does anybody know how we
may go about doing that? | 1,765.31 | 3.37 |
The hint being that in order
to control layout what we use | 1,768.68 | 2.687 |
is this thing called Flexbox. | 1,771.367 | 1.208 |
So by default components
will grow to however big | 1,775.66 | 4.83 |
they need to be in order
to fit their children. | 1,780.49 | 3.48 |
But we have a way of saying, hey fill
as much space as you possibly can. | 1,783.97 | 4.69 |
And the way to do that
is saying flex: 1. | 1,788.66 | 3.65 |
And so we want the app container
to have a flex value of 1 | 1,792.31 | 3.94 |
so that the app container
fills up all possible space. | 1,796.25 | 4.4 |
And so we could do something like
app container let's do flex: 1. | 1,800.65 | 4.59 |
And then maybe for the TODOs,
the scroll view here, maybe we | 1,805.24 | 5.67 |
want that to fill as well. | 1,810.91 | 1.97 |
And so we could go
down to the scroll view | 1,812.88 | 2.74 |
and say the style is
going to be flex: 1. | 1,815.62 | 5.61 |
But that isn't great design. | 1,821.23 | 2.61 |
What if we wanted instead to just have
a style called Fill, which will just | 1,823.84 | 5.43 |
fill whatever space is available. | 1,829.27 | 2.49 |
And so that would be a
good abstraction to have. | 1,831.76 | 2.772 |
So here we have a TODO container,
we have an app container, | 1,834.532 | 2.458 |
and let's actually create this style
called Fill, which we'll just flex: 1. | 1,836.99 | 4.37 |
And so now we can say hey, we
want this scroll view to fill | 1,845.8 | 9.34 |
and we also want our
app container to fill. | 1,855.14 | 5.37 |
But instead of adding
that to app container, | 1,860.51 | 3.23 |
what would be a better way to do it? | 1,863.74 | 1.78 |
Well, we can actually
apply both those styles. | 1,865.52 | 1.98 |
Does anybody remember how we could
do that, apply multiple styles | 1,867.5 | 3.09 |
to the same component? | 1,870.59 | 1.666 |
So in React Web we would actually
just give it multiple classes. | 1,875.68 | 4.49 |
What is the analog in React Native? | 1,880.17 | 1.64 |
We can actually just pass an array. | 1,884.88 | 2.18 |
And so say first apply
styles.Appcontainer and then apply | 1,887.06 | 3.58 |
styles.fill. | 1,890.64 | 0.75 |
And now, if we add a
bunch of TODOs we can | 1,894.63 | 4.23 |
see that it fills the available space. | 1,898.86 | 2.4 |
And then if we delete TODOs such that
it doesn't fill the available space | 1,901.26 | 3.96 |
we see that it's not getting
cut off at the bottom | 1,905.22 | 3.06 |
because it's filling all the way
down to the bottom of this container. | 1,908.28 | 5.64 |
So any questions on event
handling, styling or moving | 1,913.92 | 4.92 |
React Web to React Native components? | 1,918.84 | 2.355 |
No. | 1,923.925 | 1.301 |
So we've been talking about
this thing called components, | 1,925.226 | 2.374 |
but we haven't really dived too
deeply into what that really means. | 1,927.6 | 4.5 |
In the past few weeks, we've
talked about how components | 1,932.1 | 2.61 |
return a node, how they
represent a discrete piece of UI, | 1,934.71 | 3.08 |
how all components should act like pure
functions with respect to their props. | 1,937.79 | 4.01 |
But that's really where we
stopped talking about components. | 1,941.8 | 2.69 |
And so this week, we're going to
dive more deeply into components | 1,944.49 | 2.73 |
and what components actually are. | 1,947.22 | 2.797 |
And so there are actually
two types of components. | 1,950.017 | 2.083 |
And we've actually seen
both of them already. | 1,952.1 | 2.05 |
So first is this thing called a
stateless functional component. | 1,954.15 | 2.92 |
You might see it abbreviated as SFC or
if you're reading blog posts online, | 1,957.07 | 3.38 |
some people call them pure
functional components. | 1,960.45 | 2.95 |
And what those are
basically just functions. | 1,963.4 | 3.65 |
So something like this
TODO that we've created | 1,967.05 | 3.06 |
is just a function that takes
in props and returns some node. | 1,970.11 | 3.72 |
It has no concept of state. | 1,973.83 | 2.676 |
And so that's why it's called a
stateless functional component. | 1,976.506 | 2.624 |
It's just a function with no state. | 1,979.13 | 2.41 |
And the second is a
react.component which | 1,984.09 | 1.86 |
we've been extending from but we
haven't really talked about it | 1,985.95 | 3.21 |
too far in depth. | 1,989.16 | 1.91 |
And so first let's talk about
stateless functional components. | 1,991.07 | 3.041 |
So this is the simplest
type of component. | 1,999.03 | 2.21 |
You should use this when
you don't need any state. | 2,001.24 | 3.24 |
And what it is is a function that
takes props and returns a node. | 2,004.48 | 4.04 |
And it shouldn't do anything other
than taking props and return a node. | 2,008.52 | 3.34 |
It should be what's
called a pure function. | 2,011.86 | 1.999 |
In other words, it should not have
any side effects, like setting a value | 2,013.859 | 3.041 |
or pushing to an array, updating
an object, something like that | 2,016.9 | 4.86 |
because it should just take
in props and return the value. | 2,021.76 | 4.2 |
If you do stuff other than that you
might create some bugs or even worse | 2,025.96 | 5.4 |
crash your app or something like that. | 2,031.36 | 3.264 |
Then, any changes to the
props that you passed | 2,034.624 | 1.916 |
to a stateless functional
component will automatically | 2,036.54 | 2.68 |
cause that function to be re-invoked. | 2,039.22 | 2.65 |
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