Prop Drilling | Lecture 107 | React.JS 🔥
Summary
TLDRThe video script discusses the concept of prop drilling in component-based development, where state or data must be passed through multiple nested components to reach the target component. It illustrates the process of moving the 'movies' state from a deeply nested 'MovieList' component to the 'NumResults' component, emphasizing the inefficiency and potential complexity of prop drilling, especially in larger and more deeply nested component trees. The script concludes by hinting at future solutions to this issue, such as component composition.
Takeaways
- 🔍 The lecture begins with an intention to fix a small problem in a previously created component and introduces the concept of prop drilling.
- 📈 A review of the previous lecture categorizes components into structural and presentational, with examples provided for each type.
- 🏗️ Structural components like App, NavBar, and Main are responsible for the layout and structure of the application.
- 🎨 Presentational components such as Logo and NumResults do not have state and are responsible for presenting content.
- 🔄 Stateful components like Search, ListBox, MovieList, and WatchedBox manage their own state.
- 🔄 The process of lifting state up to the closest parent component is highlighted as a solution to sharing state across components.
- 💡 The concept of prop drilling is introduced as the need to pass props through multiple nested child components to reach a deeply nested component.
- 🛠️ The script demonstrates prop drilling by passing the 'movies' array down through Main, ListBox, and finally to MovieList.
- 🚧 The inefficiency and potential complexity of prop drilling are discussed, especially when dealing with deeply nested component trees.
- 🔧 The lecture concludes with a mention of future solutions to prop drilling, such as component composition, to be explored in the next lecture.
Q & A
What is the main issue discussed in the script?
-The main issue discussed is the problem of prop drilling, which occurs when a state or prop needs to be passed through multiple nested components to reach a deeply nested component that requires it.
How does the script categorize the components of the application?
-The script categorizes components into structural and presentational components. Structural components are responsible for the layout of the application, while presentational components are stateless and only present content, and stateful components that manage their own state.
What is the solution proposed to the problem of prop drilling?
-The solution proposed is to lift the state up to the closest parent component and then pass it down as a prop to where it is needed, which in this case is the App component.
Why is prop drilling considered a problem?
-Prop drilling is considered a problem because it leads to unnecessary complexity and redundancy. Components that do not need the prop still have to receive and pass it down, which can become unmanageable as the component tree becomes deeper.
What is the significance of the 'movies' state in the script?
-The 'movies' state is significant because it is the data that needs to be passed down through multiple components to display the number of results. It is used to demonstrate the process of prop drilling and the need for a solution to this problem.
How does the script illustrate the process of prop drilling?
-The script illustrates prop drilling by showing the steps of passing the 'movies' state from the MovieList component up to the App component and then down to the NumResults and MovieList components again, which is a tedious process especially for deeply nested components.
What is the alternative solution to prop drilling mentioned in the script?
-The alternative solution mentioned is component composition, which will be explored in the next lecture as a way to avoid the issues associated with prop drilling.
How does the script demonstrate the concept of a stateless component?
-The script uses the Logo component as an example of a stateless or presentational component, which does not have any state and simply presents content without managing any state.
What is the role of the App component in solving the prop drilling issue?
-The App component is the closest parent component to both MovieList and NumResults. It is responsible for lifting the state up and then passing it down as a prop to the necessary child components, thus mitigating the prop drilling problem.
What is the final outcome after addressing the prop drilling issue?
-After addressing the prop drilling issue, the script successfully displays the correct number of results (three results in the example), demonstrating that the state has been passed effectively through the component hierarchy.
How does the script set the stage for future learning?
-The script sets the stage for future learning by introducing the concept of component composition as a potential solution to the problem of prop drilling, which will be explored in subsequent lectures.
Outlines
🔍 Problem Identification and Component Classification
The speaker begins by acknowledging a small issue in a previously created component and proposes to address it. This serves as an opportunity to review the previous lecture, where each component is categorized into structural or presentational. Structural components like the App, NavBar, and Main are responsible for the layout, while presentational components like the Logo, NumResults, and MovieList handle content presentation and state management. The speaker identifies that the ListBox, MovieList, and WatchedBox are stateful components, and the Movie component is stateless, simply displaying data. The main issue highlighted is the lack of dynamic calculation for the number of results, which requires access to the movies state in NumResults. The solution involves lifting the state up to the closest parent component, which is the App component, and then passing it down as a prop through the necessary components, introducing the concept of prop drilling.
🛠️ Tackling Prop Drilling and its Challenges
The speaker delves into the concept of prop drilling, explaining it as the process of passing a prop through multiple nested child components to reach a deeply nested component. This is demonstrated by the need to pass the 'movies' prop from the Main component down to the MovieList. The speaker points out that this can become cumbersome and inefficient when the data structure is nested deeply, potentially spanning 5 to 10 levels. The speaker also notes that while the current solution works, it is not optimal due to the extensive prop drilling involved. The lecture concludes with a teaser for the next session, where a more efficient solution to prop drilling through component composition will be discussed.
Mindmap
Keywords
💡structural components
💡presentational components
💡stateful components
💡prop drilling
💡lifting state up
💡component composition
💡component hierarchy
💡props
💡state
💡data flow
Highlights
The lecture begins by addressing a small problem in a previously created component.
The process involves fixing the problem and discovering the concept of prop drilling.
A quick review of the previous lecture classifies components into structural and presentational categories.
The App and NavBar components are identified as structural components responsible for layout.
The Logo and NumResults are presentational components, stateless and focused on content presentation.
The Search and ListBox components are stateful, holding and managing their state.
The Movie component is stateless, receiving props and presenting data without state management.
The issue of not dynamically calculating the number of results is highlighted.
The solution involves accessing the movies state in the NumResults component.
Lifting the state up to the closest parent component is suggested as a solution to the problem.
The App component is identified as the closest parent where the state should be lifted to.
Prop drilling is introduced as the challenge of passing props through nested components.
The process of prop drilling is demonstrated by passing the movies array through multiple components.
The inefficiency and potential complexity of prop drilling are discussed, especially with deeper nesting.
The lecture concludes with a mention of future solutions to prop drilling, such as component composition.
Transcripts
Now we left a small problem
in one of the components that we just created earlier.
And so let's now go fix that problem, and in the process,
discover the problem of prop drilling.
But before we go do that,
I just want to very quickly review the previous lecture
by classifying each of our components
into one of the categories that we just looked at.
So I think that clearly both the App
and the NavBar component here are structural components.
So they're only responsible for the structure
or for the layout of the application.
And the same can also be set of this Main component here.
So those are for providing structure.
Then the logo here
is clearly a presentational component,
so it doesn't have any state,
and so therefore it's stateless.
And it simply presents some content here.
Then the Search is, of course, a stateful component.
Then NumResults is just a presentational component here.
Main we already talked about.
Then we have the ListBox,
which clearly is a stateful component,
and the same for the MovieList and for the WatchedBox.
So those are all stateful components,
while the Movie simply receives this prop right here
and then presents that data in the user interface.
And so Movie here is just a stateless
or presentational component.
Then we have this one here,
which is also a presentational component,
and the same for this one,
so WatchedMoviesList and WatchedMovie.
All right, and that's actually it.
I just wanted to quickly categorize each of them,
but now let's move on
to that problem that I mentioned in the very beginning.
And that is that right now
here we are not dynamically calculating
the number of results.
So we are not basically taking the list of movies
and reading how many there are, and then displaying it here.
So that's what we want to do.
But yeah, now we only have this X.
So what we need, basically,
is to get access to the movies state
right here in NumResults.
Now, where does that state live right now?
Well, it's here inside of MovieList,
so right here.
So, again, it's here, but we also need it here
in NumResults.
So what's the solution to that?
And I really hope you already know at this point.
Well, the solution is to lift the state up
to the closest parent component.
And what parent is that?
Well, it's the App component, right?
So it's not the NavBar,
because, of course, that's not a parent of MovieList.
And so it is really the App component.
So what we need to do
is to cut this from here
and place it right back into the App component.
All right?
And now we need to pass it down as a prop
to where we need it.
And so this is where the problem of prop drilling
will come into play.
So, again, we need now this state
in order to make this work again inside of the MovieList.
But this MovieList is really deeply nested
inside this component tree, right?
So it has these two parent components,
which now will also need to receive that state as a prop.
But instead of talking, let's actually do this.
So movies={movies}.
So now we have the movies array inside Main,
so let's go there.
And we need to receive it here,
and then we need to pass it here
right into the WatchedBox
or actually into the ListBox.
So movies={movies},
or actually here, yeah
it's not main, of course, it's movies.
Okay, so now we got it inside the Main,
and now we got it inside the ListBox.
So let's come here and do it all again.
So accepting it here
and then passing it here.
So movies={movies}.
And so what we are doing right now
is what we call prop drilling.
So now we finally accept it here, and then it works again.
So basically prop drilling means
that we need to pass some prop
through several nested child components
in order to get that data into some deeply nested component,
which in this case is this one.
So we had to pass this movies prop here first into the Main,
then, well, from the Main into the ListBox,
and then from the ListBox into the MovieList.
And so all these components,
they didn't actually even need this prop.
All they needed this for
was to then pass it down even further the tree.
And so we end up with a lot of props
that are really not needed at all.
All they are needed for
is to pass the data down even further
into our component tree.
So this is what prop drilling is.
And you saw that it is not a lot of fun,
and it could be even worse, of course,
if the data was nested even deeper into the tree.
So this was just like three levels deep,
but it could be like 5 or 10 levels.
And so then it would become a little bit out of control.
So we will look at ways of fixing prop drilling
a bit later in this section,
but, for now, let's finally also make this prop,
so this movies data,
available right here where we also need it.
So right here.
So movies={movies}.
So now we have to do some prop drilling again,
because here we need to again accept this prop,
but we don't need it here.
All we need it for is to pass it down again.
But here it's not so bad,
because it's really just one level.
Okay, and now, finally, movies.length.
And so ta-da, we got three results.
Nice. So this works.
And what we just did here
is a perfectly valid solution
to make the application work, of course.
But, as I mentioned,
what we did was some so-called prop drilling,
which is not always the best solution,
especially if we need
to pass that prop down really, really deep into the tree.
And so in the next lecture,
we will take a look
at one of the possible solutions to this problem,
which is component composition.
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