pre-view/CS50-raw · Datasets at Hugging Face

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

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