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

text stringlengths 1 81	start float64 0 10.1k	duration float64 0 24.9
So all of the React Native components, the React components sorry,	875.58	3.88
we've changed to React Native components and now we have--	879.46	3.388
Oops, something's breaking still.	882.848	2.322
Prompt is another one of those browser APIs	890.42	3.9
that just does not exist in the React Native world which	894.32	2.7
caused our code to crash.	897.02	1.39
And so rather than using one of these browser	898.41	2.96
APIs let's just replace it with some hard coded text for now,	901.37	3.21
maybe something like to do, number, and then whatever it's ID is.	904.58	8.15
And rather than incrementing ID down there	916.511	1.749
let's actually increment it up here.	918.26	1.5
And so now it works.	922.51	1.15
So we have to do number one, to do number two	923.66	2.42
and you can see how we add those.	926.08	3.31
And so we'll fix the style in the future,	929.39	2.1
but basically does anybody have questions	931.49	2.64
on going from React Web to React Native?	934.13	3.39
What we did there was just replace all the React Web components	937.52	3.36
with the React Native components.	940.88	1.89
And it is almost as easy as command effing and replacing like that.	942.77	4.52
Great.	951.291	0.499
And so how are you going to go about styling those components?	951.79	3.27
So in React Web the way we did that was just	955.06	2.9
by adding a class name and then styling in CSS, but in React Native	957.96	3.89
we don't have this concept of CSS.	961.85	3.492
So the way that React Native handles that	965.342	1.708
is by actually using JavaScript objects for styling and what that gives us	967.05	3.33
is the ability to use dynamic styles.	970.38	4.11
Object keys in these objects are based on CSS properties,	974.49	3.35
so we have stuff like margin top, margin bottom, margin padding.	977.84	5.726
And the layout system that we used is Flexbox	983.566	1.874
and so, if you're familiar with the Flexbox system in web,	985.44	2.416
it's almost exactly the same in React Native.	987.856	3.104
One of the key differences is that rather than	990.96	3.06
defaulting to row we default to laying out things in columns.	994.02	7.48
So, in React Web, we have this concept of pixels or percentages,	1,001.5	3.52
but in React Native we actually use unit-less numbers for length.	1,005.02	4.36
Which is good because there are so many different devices	1,009.38	3.48
that this runs on with different pixel densities	1,012.86	2.19
that having a unit-less number allows us to abstract that pixel density out.	1,015.05	4.18
The style prop, so the way that you style a given component	1,022.52	3.72
is by assigning that JavaScript object to a style prop	1,026.24	3.89
and it can actually take an array of styles.	1,030.13	1.87
And so, if you wanted to have a bunch of different class names in React Web	1,032	3.78
you'd just start adding those with a space in between.	1,035.78	3.6
But in React Native you handled that by passing an array of styles.	1,039.38	3.075
So let's go ahead and add styles to this app that we have here.	1,045.109	7.121
So first, let's go ahead and style this view.	1,052.23	2.24
And so right now, as you see, each to do has a Delete button and a	1,054.47	6.27
to do right under it, whereas in web we had the Delete button next to that	1,060.74	4.24
to do.	1,064.98	0.5
And so let's try to figure out exactly how we	1,065.48	2.32
can get that Delete button over here and the to do to be next to it.	1,067.8	4.7
And so does anybody have any ideas about how we might want to do that?	1,072.5	4.59
We know we're going to have to pass a style prop,	1,077.09	2.43
and we know that it's going to be an object.	1,079.52	3.45
And so this looks weird to have those double curlies	1,082.97	2.46
but the outer curlies mean, hey here comes	1,085.43	2.7
some JavaScript and the inner curlies are just an object	1,088.13	3.06
literal like we've seen before.	1,091.19	2.88
And so how might we get those to dos to be in a row?	1,094.07	3.61
So we saw before that React Native uses Flexbox in order to handle it's layout.	1,100.35	6.81
And so we can just say, hey we want the flex direction, rather than being	1,107.16	6.63
column by default, let's set it to row.	1,113.79	2.818
And so now we have the Delete button next to the to do.	1,119.42	5.19
But it's annoying me a little bit how that button is slightly below the text.	1,124.61	5.77
And so how might we get those items to be aligned to center?	1,130.38	5.36
Well in Flexbox we have this thing called align items	1,135.74	6.12
and then you just say, hey align those to be center.	1,141.86	3.66
Then all of a sudden we have it aligned center.	1,145.52	2.27
And just confirming that delete button does indeed work.	1,151.55	3.841
Great.	1,155.391	0.499
Anybody notice any other bad style bugs over here?	1,155.89	3.45
So look at this.	1,161.89	3.25
So most phones will have some nav bar, and that nav bar	1,165.14	5.72
will have stuff like if you're connected to Wi-Fi, the time and etc.	1,170.86	3.87
But that first view is actually going all the way to the top.	1,174.73	3.95
And so how might we get all this content to be slightly moved down?	1,178.68	3.46
So how would we do that in Web?	1,186.29	2.75
AUDIENCE: Add a margin.	1,189.04	1.98
SPEAKER 1: Yeah we would add a margin or some padding or something	1,191.02	2.75
to move the content from the top slightly down.	1,193.77	4.09
And so we could do that in React Native as well.	1,197.86	3.68
So you can say with this view, let's actually put a padding on the top	1,201.54	7.57
and let's just say something like 50 which is somewhat arbitrary.	1,209.11	4.741
And now we've gone ahead and moved that down slightly.	1,213.851	2.249
But what if we wanted to move it down exactly the same amount as the status	1,219.46	6.08
bar?	1,225.54	0.5
Well there's this great tool called Expo which	1,228.96	2.85
we'll talk about in length later today.	1,231.81	1.84
They're also the people who designed Snack.	1,233.65	2.3
And they actually give you this thing called constant	1,235.95	2.61
so we can do import constants from Expo.	1,238.56	3.515
And we can actually say, hey padding top rather	1,245.56	2.2
than assigning an arbitrary value of 50 let's do constants.statusbarheight	1,247.76	8.76
and that will actually give you that exact status bar height	1,256.52	4.05
even if you're on different phones.	1,260.57	2.174
And so, again, we'll talk about Expo and we'll	1,262.744	1.916
talk about importing and exporting later today.	1,264.66	3.17
But just FYI there's this thing called constants.statusbarheight which will	1,267.83	3.99

So all of the React Native components, the React components sorry,

875.58

3.88

we've changed to React Native components and now we have--

879.46

3.388

Oops, something's breaking still.

882.848

2.322

Prompt is another one of those browser APIs

890.42

3.9

that just does not exist in the React Native world which

894.32

2.7

caused our code to crash.

897.02

1.39

And so rather than using one of these browser

898.41

2.96

APIs let's just replace it with some hard coded text for now,

901.37

3.21

maybe something like to do, number, and then whatever it's ID is.

904.58

8.15

And rather than incrementing ID down there

916.511

1.749

let's actually increment it up here.

918.26

1.5

And so now it works.

922.51

1.15

So we have to do number one, to do number two

923.66

2.42

and you can see how we add those.

926.08

3.31

And so we'll fix the style in the future,

929.39

2.1

but basically does anybody have questions

931.49

2.64

on going from React Web to React Native?

934.13

3.39

What we did there was just replace all the React Web components

937.52

3.36

with the React Native components.

940.88

1.89

And it is almost as easy as command effing and replacing like that.

942.77

4.52

Great.

951.291

0.499

And so how are you going to go about styling those components?

951.79

3.27

So in React Web the way we did that was just

955.06

2.9

by adding a class name and then styling in CSS, but in React Native

957.96

3.89

we don't have this concept of CSS.

961.85

3.492

So the way that React Native handles that

965.342

1.708

is by actually using JavaScript objects for styling and what that gives us

967.05

3.33

is the ability to use dynamic styles.

970.38

4.11

Object keys in these objects are based on CSS properties,

974.49

3.35

so we have stuff like margin top, margin bottom, margin padding.

977.84

5.726

And the layout system that we used is Flexbox

983.566

1.874

and so, if you're familiar with the Flexbox system in web,

985.44

2.416

it's almost exactly the same in React Native.

987.856

3.104

One of the key differences is that rather than

990.96

3.06

defaulting to row we default to laying out things in columns.

994.02

7.48

So, in React Web, we have this concept of pixels or percentages,

1,001.5

3.52

but in React Native we actually use unit-less numbers for length.

1,005.02

4.36

Which is good because there are so many different devices

1,009.38

3.48

that this runs on with different pixel densities

1,012.86

2.19

that having a unit-less number allows us to abstract that pixel density out.

1,015.05

4.18

The style prop, so the way that you style a given component

1,022.52

3.72

is by assigning that JavaScript object to a style prop

1,026.24

3.89

and it can actually take an array of styles.

1,030.13

1.87

And so, if you wanted to have a bunch of different class names in React Web

1,032

3.78

you'd just start adding those with a space in between.

1,035.78

3.6

But in React Native you handled that by passing an array of styles.

1,039.38

3.075

So let's go ahead and add styles to this app that we have here.

1,045.109

7.121

So first, let's go ahead and style this view.

1,052.23

2.24

And so right now, as you see, each to do has a Delete button and a

1,054.47

6.27

to do right under it, whereas in web we had the Delete button next to that

1,060.74

4.24

to do.

1,064.98

0.5

And so let's try to figure out exactly how we

1,065.48

2.32

can get that Delete button over here and the to do to be next to it.

1,067.8

4.7

And so does anybody have any ideas about how we might want to do that?

1,072.5

4.59

We know we're going to have to pass a style prop,

1,077.09

2.43

and we know that it's going to be an object.

1,079.52

3.45

And so this looks weird to have those double curlies

1,082.97

2.46

but the outer curlies mean, hey here comes

1,085.43

2.7

some JavaScript and the inner curlies are just an object

1,088.13

3.06

literal like we've seen before.

1,091.19

2.88

And so how might we get those to dos to be in a row?

1,094.07

3.61

So we saw before that React Native uses Flexbox in order to handle it's layout.

1,100.35

6.81

And so we can just say, hey we want the flex direction, rather than being

1,107.16

6.63

column by default, let's set it to row.

1,113.79

2.818

And so now we have the Delete button next to the to do.

1,119.42

5.19

But it's annoying me a little bit how that button is slightly below the text.

1,124.61

5.77

And so how might we get those items to be aligned to center?

1,130.38

5.36

Well in Flexbox we have this thing called align items

1,135.74

6.12

and then you just say, hey align those to be center.

1,141.86

3.66

Then all of a sudden we have it aligned center.

1,145.52

2.27

And just confirming that delete button does indeed work.

1,151.55

3.841

Great.

1,155.391

0.499

Anybody notice any other bad style bugs over here?

1,155.89

3.45

So look at this.

1,161.89

3.25

So most phones will have some nav bar, and that nav bar

1,165.14

5.72

will have stuff like if you're connected to Wi-Fi, the time and etc.

1,170.86

3.87

But that first view is actually going all the way to the top.

1,174.73

3.95

And so how might we get all this content to be slightly moved down?

1,178.68

3.46

So how would we do that in Web?

1,186.29

2.75

AUDIENCE: Add a margin.

1,189.04

1.98

SPEAKER 1: Yeah we would add a margin or some padding or something

1,191.02

2.75

to move the content from the top slightly down.

1,193.77

4.09

And so we could do that in React Native as well.

1,197.86

3.68

So you can say with this view, let's actually put a padding on the top

1,201.54

7.57

and let's just say something like 50 which is somewhat arbitrary.

1,209.11

4.741

And now we've gone ahead and moved that down slightly.

1,213.851

2.249

But what if we wanted to move it down exactly the same amount as the status

1,219.46

6.08

bar?

1,225.54

0.5

Well there's this great tool called Expo which

1,228.96

2.85

we'll talk about in length later today.

1,231.81

1.84

They're also the people who designed Snack.

1,233.65

2.3

And they actually give you this thing called constant

1,235.95

2.61

so we can do import constants from Expo.

1,238.56

3.515

And we can actually say, hey padding top rather

1,245.56

2.2

than assigning an arbitrary value of 50 let's do constants.statusbarheight

1,247.76

8.76

and that will actually give you that exact status bar height

1,256.52

4.05

even if you're on different phones.

1,260.57

2.174

And so, again, we'll talk about Expo and we'll

1,262.744

1.916

talk about importing and exporting later today.

1,264.66

3.17

But just FYI there's this thing called constants.statusbarheight which will

1,267.83

3.99