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I am displaying contact list array.
If contacts array is empty it will show the loader else will display contact list.
I render loader using higher order component Using this tutorial. For this I got performance summary as shown in the below image-
when i render loader using simple if else condition then i had performance graph as below -
comparing this i got to know that while using higher order component it requires more time than simple loop.
Can anyone please explain me which is better to use ? and when we should use the Higher order component ? what are advantages and disadvantages of using Higher order component ?
A higher order component allows you to apply functionality or data that is common amongst a number of components to a component and will return a new component with the functionality or data of the HoC included.
As for advantages or disadvantages. Would entirely depend on the circumstance and problem you are trying to address. You would also need to perform a long list of tests as the times are too close to really say one is quicker than the other. Also this looks like it is on your local so on production server could be an entirely different story.
But in your circumstance are you apply any extra functionality to your <Loader /> component? If you aren't or that functionality is not going to be used anywhere else then it might be unnecessary to use a HoC in your case.
ReactJS - Higher Order Components
pros for HOC:
extremly reusable around your app/projects:
// withShowSupport.js
export default Component => props =>
!props.show
? null
: <Component { ...props } />
easy testing
res:
https://www.robinwieruch.de/gentle-introduction-higher-order-components/
New technology can lead us to be more efficient and effective in productivity. But, of course, it will also increase resource usage.
I don't have enough knowledge to explain more, but I can give you simple study case.
I have a react app which consists of several pages (how about > 10 pages?). I want to do something when each page has been rendered (In other words, page changes). If-else condition rendering? No way!
Actually, you can make an HOC named withBase that will wrap each page (Use it when you export your page component e.g. export default withBase(Home)). withBase will execute a function that indicates page has been changed.
DEMO
As per definition :
HOC is a function that accepts your component as an argument and
returns a new function that adds some feature to the component.
A simple use case is - when you call an API to fetch some data and use them to render some content in your application, we need to show some kind of progress bar, loading indicator, etc to tell users that data is being fetched. We can use HOC for that purpose.A sample code goes here
import React from 'react';
import List from './List.js';
import WithLoading from './WithLoading.js';
const ListWithLoading = WithLoading(List);
class App extends React.Component {
state = {
loading: false,
repos: null
}
componentDidMount() {
this.setState({ loading: true });
fetch(`https://api.github.com/users/farskid/repos`)
.then(json => json.json())
.then(repos => {
this.setState({ loading: false, repos: repos });
});
}
render() {
return (
<ListWithLoading isLoading={this.state.loading} repos={this.state.repos} />
)
}
}
the above is App.js file and below is the HOC component WithLoading
import React from 'react';
function WithLoading(Component) {
return function WihLoadingComponent({ isLoading, ...props }) {
if (!isLoading) return (<Component {...props} />);
return (<p>Be Hold, fetching data may take some time :)</p>);
}
}
export default WithLoading;
so in App.js, we are calling HOC like const ListWithLoading = WithLoading(List); and <ListWithLoading isLoading={this.state.loading} repos={this.state.repos} />, Where List is the component which is passing into the HOC. based on the sLoading prop, loding symbol is shown. Another one interesting thing is HOC dont have a render menthod! beacuse its a simple function !
By my understanding, Higher-Order-Component adds an additional layer between components or libraries for better code-reuse.
For example, you have a library file "User.class.js" that is responsible to retrive/store user data, and it's used by different components. When "User.class.js" is modified, method names changed, or parameters changed. What you gonna do? Apply changes to all those components? What if it's used by 100 different components, or even more? With Higher-Order-Component, you just need to apply the changes to one single file.
Related
I have three components, each using the same two queries (custom hooks):
const {
data: survey,
isLoading: isSurveyLoading,
isError: isSurveyError,
} = useSurveyInfo(id);
const {
data: responses,
isLoading: isResponsesLoading,
isError: isResponsesError,
} = useResponses(id);
In each of these 3 components, I'm showing a loading spinner in the case of isLoading
How do I show one loading spinner for all three components?
I know I could use the queries in the parent component and pass props to children. But to eliminate prop drilling, I am calling each query in the child component (which seems to be best practice).
Is there a way to show one loading spinner when any of the 3 child components is loading?
Suspense is made for this, but it's still experimental
https://tanstack.com/query/v4/docs/guides/suspense
One of beauties of react-query is that it allows you to render multiple components that relay on the same data and updates all the components at the same time since they all rely on the same provider.
But now the job to make it look good on the website is on us.
I suggest not rendering the loader from the 2 lower components in the page.
Or if it makes no sense to have a content less component, you can always return null from the components.
const SecondAndTheirComponents = () => {
const { isLoading: isResponsesLoading } = useResponses(id);
if (isResponsesLoading) {
return null;
}
return (
<Content
...
/>
);
};
Or better yet: I would recommend looking into adding skeletons when you are loading data. This way you could save the space for all component and avoid jumpiness when data is returned to the browser.
You can checkout the skeletons by Material-ui (both v3 and v4 work perfectly fro me) v4 skeletons-material
According to your first question loading one spinner for all three components, you can use if else condition of reactjs, for example-
{
isResponseLoading?
isSurveyLoading?
<RunSpinnerCode/>
:
null
}
As shown in the above we can check two and even more condition. If first one is loaded, then we check for second one and so on..
Hope you like the answer if you still face any issue, just lemme know.
Thanks
Lately I've been trying to write my React components as "Pure Functions" and I've noticed that sometimes I want to have something which feels a lot like state. I was thinking about passing my state as a second parameter to my component. I can achieve this by calling my component as a normal function with two parameters, props and state.
For example:
// abstracted to it's own module
const useState = (Component, state = {}) => {
return class extends React.Component {
state = createState(this, state); // will traverse and update the state
render() {
const { props, state } = this;
return Component(props, state); // <-- call the Component directly
}
};
};
const Component = (props, { index, increase }) => (
<div onClick={increase} {...props}>
Click me to increase: {index}
</div>
);
const componentState = {
index: 0,
increase: (event, state) => ({ ...state, index: state.index + 1 })
};
const StatefullComponent = useState(Component, componentState);
<StatefullComponent style={{ color: "purple" }} />;
I have a CodeSandbox example:
My questions are:
Will this pattern harm performance?
I'm no longer extending the props with state values, this might be a good thing
I am messing with the way components are rendered by default, this might be a bad thing
Will this Pattern break things like shouldComponentUpdate? (I have a sinking feeling this is modelling the old context api)
How worried should I be that future react updates will break this code?
Is there a more "Reacty" way of using State in a Pure function without resorting to libraries like Redux?
Am I trying to solve something which should not be solved?
Note: I'm using state in this example, but it could also be a theme, authorisation rules or other things you might want passed into your component.
EDIT 19-03-2018: I have noticed that people seem to be confused about what I'm asking. I'm not looking for a new framework or a conversation about "why do you want to separate your concerns?". I am quite sure this pattern will clean up my code and make it more testable and "cleaner" in general. I really want to know if the React framework will in any way hinder this pattern.
At first glanced when I checked your code I had a question:
"Why do you make it so complicated? When you can simply make it with a class declaration".
But later when I have splitted your code I found it really worth to do that.
Question 1: Doesn't really make a difference, it is the way how HOC does the composition.
I'm no longer extending the props with state values, this might be a good thing
Why/When might it be a good thing?
I am messing with the way components are rendered by default, this might be a bad thing
I don't see that you break or mess the rendering by default, I think the HOC pattern promotes the same philosophy, the difference you separate state from props.
Question 2: If a developer decide to use a stateless component then he/she should realize all “lifecycle methods” or references ref will be not available.
Your pattern make stateless component as “statefull” but in stateless declaration - amazing 😋.
Like in JSX you write in JS an "HTML" and inside it JS code with another "HTML":
<ul>
{list.map(text => <li>text</li>)} // I know there should be used key
</ul>
Mr. Baudin pattern (state-full like stateless):
import React from 'react'
import {useState} from './lib'
const state = {
index: 0,
increase: (event, state) => ({index: state.index + 1})
}
const Component = (props, state) => (
<div onClick={state.increase} {...props}>
Click me to increase: {state.index}
</div>
)
export default useState(Component, state)
Question 3: It depends what break changes will be in coming versions.
Question 4: Well... I don't think the offered pattern (implemented library) can be considered as application state management but it can be used within any state management like Redux or Mobx because it deals with internal component state.
Question 5: No, I don't think. Your solution makes code less and clean. Functional components are good for very simple or representational components and now it can be extended with state.
While this question has been open I've done some painful research on the subject and I'd like to share this research with you.
Question 1: Performance; Calling your components as functions or even as constructor functions doesn't really make a difference. You simply get your component instead of a type.
// the component
const MyComponent = () => (<div>This is my page</div>);
console.log(MyComponent());
console.log(new MyComponent());
console.log(<MyComponent />);
console.log(React.createElement(MyComponent));
Pen (Don't forget to inspect the developer tools!)
What I've noticed is that when you call a component directly you lose a little information, for example, when I use JSX the type information is preserved:
React.createElement(MyComponent).type === MyComponent // <- true
MyComponent() // <- Now way to find out what constructed this...
This doesn't seem like a big deal because the MyComponent() is seen as a normal div so it should render correctly; but I can imagine that React might do some lookup on the type of the component and calling your function like this that might interfere with the performance.
Haven't found anything in the documentation nor in the source code to suggest that this is the case, so I see no reason to worry about performance at this point.
Question 2: Does this break shouldComponentUpdate; the answer is "maybe not", but not because I need to write a class as was suggested. The problem is that React does a shallow compare on the props when you use a PureComponent and with pure functions just expects that with the same props you get the same result. In my case, because of the second parameter it might think the component doesn't need to update but actually it should. Because of some magic in my implementation this seems to work for child components of a root component wrapped with the useState function.
This is as I expected the same problem as with the original implementation of the context api. And as such I should be able to solve it using some reactive techniques.
Question 3: Seeing how "just calling a component as a function" seems to be the entire idea behind react and seeing how it results in almost exactly the same component without the original type information I see no reason why this should break in the future.
Question 4/5: No, there is no more "Reacty" way of really solving this problem. There is how ever a more functional way. I could use a state monad and lift the entire thing up; but that would envolve a lot of work and I really can't see the benefit of doing that. Passing state as a second parameter seems, at least for now, as something which might be strange but viable and actually feasable.
Question 5: When I started looking around I didn't find a lot os answers to these questions, but now that I've really dug myself in I can see a few other libraries doing the same thing. For example: recompose which calls itself "lodash for react". They seem to use this pattern of wrapping your component in a function and returning a class a lot. (Their withState implementation).
Extra information: My conclusion is that this pattern (because it's nothing more than a pattern) is valid and does not break any fundamental rules of React. Just to give a little bit of extra information Bernardo Ferreira Bastos Braga wrote that I needed to use a class to do it "the React way". I fail to see how wrapping your function and returning a class with state is anything other than "using a class".
I do however realise that wrapping a function increases complexity, but not by much; function calls are really optimised and because you write for maintainability and optimise later.
One of my biggest fears is that when the software gets more and more complocated and we get more cross-cutting concerns to deal with, it will get harder and harder to handle every concern as a parameter. In this case it might be good to use a destructuring pattern to get the concerns which you need from a "concerns" obejct passed as the second parameter.
One last thing about this pattern. I've done a small test (Just selenium rendering a page a 100 times) and this pattern, on a small scale, is faster than using Redux. The bigger your redux state gets and the more components you connect the faster this pattern becomes. The down side is that you are now doing a bit of manual state management, this comes with a real cost in complexity. Just remember to weigh all options.
A few examples of why this state component
Applications which interact with users, require that you try to keep track of the interactions they have. These interactions can be modeled in different ways but I really like a stateful approach. This means that you 'thread' state through your application. Now in react you have a few ways of creating components. The three I want o mention are:
create a class and extend from Component
create a class and extend from PureComponent
create a stateless function
I really like the last option but, to be honest, it's a pain keeping your code performant. There are a lot of articles our there explaining how lambda expression will create a new function every time your component is called, breaking the shallow compare of the props done by PureComponent.
To counteract this I use a pattern where I wrap my stateless component in a HoC where I pass my component and my state object. This HoC does some magic and passes the state as a second parameter to the stateless function, ensuring that when the props are tested by the compare of the PureComponent it should work.
Now to make the wrapper even better I memoize the lambdas so that only a single reference to that function exists so that even if you were to test the function by reference it should still be OK.
The code I use for this is:
return Object.entries(_state).reduce(
(acc, entry) => {
const [key, value] = entry;
if (value instanceof Function) {
acc[key] = _.memoize(item => (...args) => {
const newState = value.apply(null, [...args, root.state, root.props]);
root.setState(newState);
});
} else {
acc[key] = value;
}
return acc;
},
{}
);
};
As you can see I memoize the function and call it proxying the arguments and passing in the state and the props. This works as long as you can call these functions with a unique object like so:
const MyComponent = useState((props, { items, setTitle }) => {
return (
<div>
{items.map(item => (
<Component key={item.id} item={item} changeItem={setTitle(item)} />
))}
</div>
);
}, state);
1- Will this pattern harm performance?
Performance is usually not a black/white, rather it is better / worse in different scenarios. Since React already has a standard way of doing this, it it plausible that you'll be missing out on internal optimizations.
2-Will this Pattern break things like shouldComponentUpdate? (I have a sinking feeling this is modelling the old context api)
Yes, you should be using the class declaration if you need to write shouldComponentUpdate functions
3- How worried should I be that future react updates will break this code?
I think is fair to say that you should, since there are obvious and documented ways of doing the same using classes.
4 - Is there a more "Reacty" way of using State in a Pure function without resorting to libraries like Redux?
you could have a container component that has state and pass down callback functions to update the state
5- Am I trying to solve something which should not be solved?
yes, since there is already a mainstream and documented way of archieving what you need using the Component class. You should probably resort to functional components only for very simple or presentational components
So, I have read multiple times: Composition is Good. Extending is Evil.
Now, I do use composition, basically a lot of stateless components and higher order components, however I do have one particular case where I extend a class.
Instead of every stateless component extending from Component, I am extending from my own BaseComponent, which basically has some helper functions that I use in all of my components.
Like for example:
Analytics helpers
Loggers
Data Fetchers
Configuration
Storage
Theme management
Actions
So far, I am happy with the result. I am looking for any good reason for me to actually break this pattern in the objective to pursuit great code.
Please no "React recommends composition" answers.
Well why not simply use HOC's for each of those pieces?
The big benefit of using HOC's for these kind of situations, is that you can apply them individually, or as a group. You gain a ton of control in how you slice/dice these shared pieces of functionality.
As a simple, example, your logger as an HOC might look something like;
const function loggerHoc(WrappedComponent) {
return class extends Component {
log(message) {
console.log(message); //or other implementation
}
render() {
<WrappedComponent log={this.log} {...this.props}/>;
}
}
}
Now if you had a second HOC of this style for analytics, they can be wrapped on top of one another without issue;
ResultComponent = loggerHoc(analyticsHoc(ChildComponent));
Which you could also write a function to do all of;
const function wrapWithAll(WrappedComponent) {
return loggerHoc(
analyticsHoc(
WrappedComponent
)
);
}
Or you can use individually, as your needs dictate.
I am struggling a bit with the concept of global state and reusable components in redux.
Let's say I have a component that's a file-selector that I want to use in multiple places inside my applications state. Creating action/reducers leads to a lot of bloat as I have to handle states with dynamic suffixes and other weird things that just don't really strike me as a smart way to go about things.
What's the general consensus on these things? I can only see two solutions:
Make the file-selector component have local state (this.setState/this.getState)
Make the file-selector be part of the global state but in it's own unique reducer that I can read from once the operation of the component is done?
Any ideas / best practices? Thanks.
Update: To clarify the file selector I am describing is not a simple component that works purely on the client side but has to fetch data from the server, provide pagination as well as filtering etc.. That's why I'd also like to reuse most of the client/server interaction. The views that display this component are of course dumb and only display values from the state - but how do I reuse the actions/reducers in multiple places around the application?
Have your reducer handle multiple instances of your component state. Simply define some "unique" ID for each instance of your FileBrowser component when it appears in the app, and wrap your current state in an object with this uniqueIds as keys, and your old complex state as value.
This is a technique I've used multiple times. If all your FileBrowser are known at compile time, you can even setup the initial state before running your app. If you need to support "dynamic" instances, simply create an Action that initializes the state for a given id.
You didn't provide any code, but here's a contrived example for a reusable Todo reducer:
function todos(state={}, action){
switch(action.type){
case 'ADD_TODO':
const id = action.todoListId
return {
...state,
[id]: {
...state[id],
todos: [ ...state[id].todos, action.payload ]
}
}
// ...
}
}
Usually, the rule of thumb is that you use a redux store to manage data in your application aka storing items fetched from the server and local react state for ui behaviors, like file uploads in your case. I'd make a pure react component to manage file uploads and then use redux-form to manage specific form.
Here is the example of the component I use in my project
import React, {Component, PropTypes} from 'react';
import Button from 'components/Button';
class FileButton extends Component {
static propTypes = {
accept: PropTypes.string,
children: PropTypes.any,
onChange: PropTypes.func.isRequired
};
render() {
const {accept, children, onChange} = this.props;
return <Button {...this.props} onClick={() => this.file.click()}>
<input
ref={el => this.file = $(el)}
type="file"
accept={accept}
style={{display: 'none'}}
onChange={onChange}
/>
{children}
</Button>;
}
}
export default FileButton;
We came to the conclusion that reusable components must be of two kinds:
dumb components, i.e. components that only receive props and trigger "actions" via props callbacks only. These components have minimal internal state or at all. These are the most frequent of reusable components, and your file selector will probably fall in that case. A styled Text Input or custom List would be good examples too.
connected components that provide their own actions and reducer. These components have their own life within the application and are rather independent from the rest. A typical example would be a "top error message box" that displays on top of everything else when the application fails critically. In such a case the application triggers an "error action" with the appropriate message as payload and on the following re-render, the message box displays on top of the rest.
As I get further into implementing redux + react into a fairly complex app which depends on many API requests to load a single page, I'm having trouble deciding whether it's better to have a single container component at the root of the page which handles all async stuff and passes props down to dumb components, v.s. having multiple container components which concern themselves only with the data they need, as well as fetching the data they need. I've gone back and forth between these two patterns and found that they each have pros/cons:
If I put a single container component at the top:
pro: All isFetching props and fetchSomeDependency() actions can be handled in one place.
con: the downside which is really annoying is that I find myself having to forward props and callbacks through multiple components, and certain components in the middle of the tree end up being tied up to this.
Here's a visual example of the issue that shows the relationships required props-wise:
<MyContainer
data={this.props.data}
isFetchingData={this.props.isFetchingData}
fetchData={this.props.fetchData}
>
{!isFetchingData &&
<MyModal
someData={props.data}
fetchData={props.fetchData}
>
<MyModalContent
someData={props.data}
fetchData={props.fetchData}
>
<SomethingThatDependsOnData someData={props.someData} />
<SomeButtonThatFetchesData onClick={props.fetchData} />
</MyModalContent>
</MyModal>
}
</MyContainer>
As you can see, <MyModal /> and <MyModalContent /> now need to be concerned with props that have nothing to do with it, seeing as a modal should be able to be re-used and only be concerned with stylistic qualities of a modal.
At first the above seemed great but once I got to 100+ components it all felt very tangled, and I found the complexity of these top-level container components to be too high for my liking, seeing as most of them (in the app I'm working on) depend on responses from 3+ API requests.
Then I decided to try multiple containers:
pro: Completely removes the need to forward props. It still makes sense to do it in some cases, but it's a lot more flexible.
pro: Way easier to refactor. I'm surprised at how I can significantly move around and refactor components without anything breaking, whereas in the other pattern things broke a lot.
pro: The complexity of each container component is much less. My mapStateToProps and mapDispatchToProps is more specific to the purpose of the component it's in.
con: Any component that depends on async stuff will always need to handle isFetching state in itself. This adds complexity that is not necessary in the pattern where its handled in a single container component.
So the main dilemma is that if I use one container, I get this un-necessary complexity in components between the root container and the leaf components. If I use multiple containers, I get more complexity in the leaf components, and end up with buttons that need to worry about isFetching even though a button should not be concerned about that.
I'd like to know if anyone has found a way to avoid both cons, and if so, what is the "rule of thumb" you follow to avoid this?
Thanks!
The way I have always seen it is to have your containers at the top most component of a logical components group other than your root/app component.
So if we have a simple search app that display results and lets assume the component heiarchy is such
<Root> <- setup the app
<App>
<Search/> <- search input
<Results/> <- results table
</App>
</Root>
I would make Search and Results redux aware containers. Because react component are suppose to be composable. You might have other components or pages that need display Results or Search. If you delegate the data fetch and store awareness to the root or app component, it make the components become dependent on each other/app. This make it harder down the line when you have to implement changes, now you have to change all the places that use them.
The exception to this is probably if you do have really tightly coupled logic between components. Even then, I would say then you should create a container that wraps your tightly coupled components since they won't be abled to be used realistically without each other.
Redux author Dan Abramov suggests that you use container components when you need them. That is, once you get to have too many props wiring up and down between components it's time to use containers.
He calls it an "ongoing process of refactoring".
See this article: https://medium.com/#dan_abramov/smart-and-dumb-components-7ca2f9a7c7d0
I wouldn't even consider using a single container approach. It pretty much entirely negates all advantages of redux. There is no need whatsoever to have a state management system if all your state is in one place and all your callbacks are in one place (root component).
I think there's a thin line to walk, though. I'm making an app where I've been at it for about 5 weeks (part time) and it's up to 3000 lines right now. It has 3 levels of view nesting, a routing mechanism i implemented myself, and components that are 10+ levels of nesting deep that need to modify state. I basically have one redux container for each big screen and it works marvelously.
However, if I click on my "clients" view, I get a clients listing which is fine, since my clients view is inside a redux container and gets the list of clients passed as props. However, when I click on one client, I'm really hesitant to do another redux container for the individual client's profile since it's only one additional level of passing props. It seems that depending on the scope of the app, you might want to pass props up to 1-2 levels past the redux container and if it's any more than that, then just create another redux container. Then again, if it's an even more complex app, then the mixing of sometimes using redux containers and some other times not using them could be even worse for maintainability. In short, my opinion is trying to minimize redux containers wherever possible but definitely not at the expense of complex prop chains, since that's the main point of using redux to begin with.
So it's been over 2 years since I've posted this question, and this whole time
I have been consistently working with React/Redux. My general rule of thumb now
is the following: Use more containers, but try to write components in such a way where they don't need to know about isFetching.
For example, here is a typical example of how I would have built a to-do list before:
function Todos({ isFetching, items }) {
if (isFetching) return <div>Loading...</div>
return (
<ul>
{items.map(item =>
<li key={item.id}>...</li>
)}
</ul>
)
}
Now I would do something more like:
function Todos({ items }) {
if (!items.length) return <div>No items!</div>
return (
<ul>
{items.map(item =>
<li key={item.id}>...</li>
)}
</ul>
)
}
This way, you only have to connect the data, and the component has no concerns about states of asynchronous API calls.
Most things can be written this way. I rarely need isFetching, but when I do it is typically because:
I need to prevent, for example, a submit button from being clicked a second time, which makes an API call, in which case the prop should probably be called disableSubmit rather than isFetching, or
I want to explicitly show a loader when something is waiting for an asynchronous response.
Now, you might think, "wouldn't you want to show a loader when items are being fetched in the above todos example?" but in practice, actually I wouldn't.
The reason for this is that in the above example, let's say you were polling for new todos, or when you add a todo, you "refetch" the todos. What would happen in the first example is that every time this happened, the todos would disappear and get replaced with "Loading..." frequently.
However, in the second example that is not concerned with isFetching, the new items are simply appended/removed. This is much better UX in my opinion.
In fact, before posting this, I went through all the UI code for an exchange interface I wrote which is quite complex and did not find a single instance of having to connect isFetching to a container component that I wrote.
You don't have to dispatch AND load your state in the same place.
In other words, your button can dispatch the async request, while another component can check if you're loading.
So for example:
// < SomeButtonThatFetchesData.js>
const mapDispatchToProps = (dispatch) => ({
onLoad: (payload) =>
dispatch({ type: DATA_LOADED, payload })
});
You'll need to have some middleware to handle a loading state. It needs to update isFetching when you're passing an async payload.
For example:
const promiseMiddleware = store => next => action => {
if (isPromise(action.payload)) {
store.dispatch({ type: ASYNC_START, subtype: action.type });
Then you can use it wherever you want:
// <MyContainer.js>
const mapStateToProps = (state) => ({
isFetching: state.isFetching
});
And load the data in your inner nested component:
// <SomethingThatDependsOnData.js>
const mapStateToProps = (state) => ({
someData: state.someData
});