I'm slowly learning React and ran into a little problem. I have created my own component (functional approach) which is represented by the grid.
Grid component has functions in it that create a new blank line. The button that should trigger the add action I had to pull higher, to the parent.
I have read a bit and would like to skip the use of refs to trigger an action from the child relative to clicking on the parent.
I wrote this code, it works as I want, but I would like to ask you to check and tell if this approach is correct or if I should do it differently.
Below I present an important fragment of the components.
const View = () => {
const [add, setAdd] = useState(() => { });
const callbackOnAdd = (handle) => {
setAdd({ onAdd: handle });
}
const handleButtonClick = useCallback(() => {
add.onAdd();
});
return (
<Grid callbackOnAdd={callbackOnAdd} />
<Button onClick={handleButtonClick} />
);
}
const Grid = ({ callbackOnAdd }) => {
...
useEffect(() => {
callbackOnAdd(() => {
addNewRow();
});
}, []);
...
};
Related
I am trying to use useEffect to rerender postList (to make it render without the deleted post) when postsCount change, but I can't get it right. I tried to wrap everything inside useEffect but I couldn't execute addEventListener("click", handlePost) because I am using useEffect to wait for this component to mount first, before attaching the evenListener.
Parent component:
function Tabs() {
const [posts, setPosts] = useState([]);
const dispatch = useDispatch();
const postsCount = useSelector((state) => state.posts.count);
useEffect(() => {
document.getElementById("postsTab").addEventListener("click", handlePost);
}, [handlePost]);
const handlePost = async (e) => {
const { data: { getPosts: postData }} = await refetchPosts();
setPosts(postData);
dispatch(postActions.getPostsReducer(postData));
};
const { data: FetchedPostsData, refetch: refetchPosts } = useQuery( FETCH_POSTS_QUERY, { manual: true });
const [postList, setPostsList] = useState({});
useEffect(() => {
setPostsList(
<Tab.Pane>
<Grid>
<Grid.Column>Title</Grid.Column>
{posts.map((post) => (
<AdminPostsList key={post.id} postId={post.id} />
))}
</Grid>
</Tab.Pane>
);
console.log("changed"); //it prints "changed" everytime postCount changes (or everytime I click delete), but the component doesn't remount
}, [postsCount]);
const panes = [
{ menuItem: { name: "Posts", id: "postsTab", key: "posts" }, render: () => postList }
];
return (<Tab panes={panes} />);
}
child/AdminPostsList component:
function AdminPostsList(props) {
const { postId } = props;
const [deletePost] = useMutation(DELETE_POST_MUTATION, {variables: { postId } });
const dispatch = useDispatch();
const deletePostHandler = async () => {
dispatch(postActions.deletePost(postId));
await deletePost();
};
return (
<>
<Button icon="delete" onClick={deletePostHandler}></Button>
</>
);
}
The Reducers
const PostSlice = createSlice({
name: "storePosts",
initialState: {
content: [],
count: 0,
},
reducers: {
getPostsReducer: (state, action) => {
state.content = action.payload;
state.count = action.payload.length
},
deletePost: (state, action) => {
const id = action.payload
state.content = current(state).content.filter((post) => (post.id !== id))
state.count--
}
},
});
Okay, let discuss this in separate comment. Key point is to decouple posts logic from wrapper component(Tabs). You should create component dedicated only to posts and render it in wrapper. Like that you can easily isolate all posts-related logic in posts-related component, for example to avoid attaching some listeners from wrapper(because it is not intuitive what you are doing and who listens for what because button is not in that same component). In separated component you will have only one useEffect, to fetch posts, and you will have one selector(to select posts from redux), and then just use that selection to output content from component.
That part <Tab panes={...} /> was the source of most of your problems, because like that you are forced to solve everything above <Tab../> and then just to pass it, which is not best practice in you case since it can be too complicated(especially in case when you could have multiple tabs). That is why you need to decouple and to create tab-specific components.
This would be an idea of how you should refactor it:
function PostsTab() {
const posts = useSelector((state) => state.posts?.content ?? []);
useEffect(() => {
// Here dispatch action to load your posts
// With this approach, when you have separated component for PostsTab no need to attach some weird event listeners, you can do everything here in effect
// This should be triggered only once
// You can maybe introduce 'loading' flag in your reducer so you can display some loaders for better UX
}, []);
return (
<div>
{/* Here use Tab components in order to create desired tab */}
<Tab.Pane>
<Grid>
<Grid.Column>Title</Grid.Column>
{posts.map((post) => (
<AdminPostsList key={post.id} postId={post.id} />
))}
</Grid>
</Tab.Pane>
</div>
);
}
function Tabs() {
return (
<div>
<PostsTab/>
{/** HERE you can add more tabs when you need to
* Point is to create separate component per tab so you can isolate and maintain tab state in dedicated component
and to avoid writing all logic here in wrapper component
* As you can see there is no need to attach any weird listener, everything related to posts is moved to PostsTab component
*/}
</div>
);
}
Ok, let's discuss what I did wrong for the future reader:
There is no need to use this weird spaghetti
useEffect(() => {
document.getElementById("postsTab").addEventListener("click", handlePost);
}, [handlePost]);
const panes = [
{ menuItem: { name: "Posts", id: "postsTab", key: "posts" }, render: () => postList }
];
for I could've used a <Menu.Item onClick={handleClick}>Posts</Menu.Item> to attach the onClick directly.
I had to use useEffect to monitor posts dependency, but .map() will automatically update its content if the array I am mapping had any changes so there is no need to use it use useEffect in this context.
I think I can use lifting state to setPosts from the child component and the change will trigger .map() to remap and pop the deleted element, but I couldn't find a way to so, so I am using a combination of redux (to store the posts) and useEffect to dispatch the posts to the store than I am mapping over the stored redux element, idk if this is the best approach but this is all I managed to do.
The most important thing I didn't notice when I almost tried everything is, I must update apollo-cache when adding/deleting a post, by using proxy.readQuery
this is how I did it
const [posts, setPosts] = useState([]);
const handlePosts = async () => {
const { data: { getPosts: postData } } = await refetchPosts();
setPosts(postData);
};
const handlePosts = async () => {
const { data } = await refetchPosts();
setPosts(data.getPosts);
};
// Using useEffect temporarily to make it work.
// Will replace it with an lifting state when refactoring later.
useEffect(() => {
posts && dispatch(postsActions.PostsReducer(posts))
}, [posts]);
const [deletePost] = useMutation(DELETE_POST_MUTATION, {
update(proxy) {
let data = proxy.readQuery({
query: FETCH_POSTS_QUERY,
});
// Reconstructing data, filtering the deleted post
data = { getPosts: data.getPosts.filter((post) => post.id !== postId) };
// Rewriting apollo-cache
proxy.writeQuery({ query: FETCH_POSTS_QUERY, data });
},
onError(err) {
console.log(err);
},
variables: { postId },
});
const deletePostHandler = async () => {
deletePost();
dispatch(postsActions.deletePost(postId))
};
Thanks to #Anuj Panwar #Milos Pavlovic for helping out, kudos to #Cptkrush for bringing the store idea into my attention
I am trying to make a hook that returns the clientX and clientY values when the mouse moves on the screen. My hook looks like this -
useMouseMove hook
const useMouseMove = () => {
const [mouseData, setMouseData] = useState<[number, number]>([0, 0])
useEffect(() => {
const handleMouse = (e: MouseEvent) => {
setMouseData([e.clientX, e.clientY])
}
document.addEventListener("mousemove", handleMouse)
return () => {
document.removeEventListener("mousemove", handleMouse)
}
}, [])
return mouseData
}
And I'm using it in another component like so,
Usage in component
const SomeComponent = () => {
const mouseData = useMouseMoveLocation()
console.log("Rendered") // I want this to be rendered only once
useEffect(() => {
// I need to use the mouseData values here
console.log({ mouseData })
}, [mouseData])
return <>{/* Some child components */}</>
}
I need to use the mouseData values from the useMouseMove hook in the parent component (named SomeComponent in the above example) without re-rendering the entire component every time the mouse moves across the screen. Is there a correct way to do this to optimise for performance?
If you're not going to be rendering this component, then you can't use a useEffect. useEffect's only get run if your component renders. I think you'll need to run whatever code you have in mind in the mousemove callback:
const useMouseMove = (onMouseMove) => {
useEffect(() => {
document.addEventListener("mousemove", onMouseMove)
return () => {
document.removeEventListener("mousemove", onMouseMove)
}
}, [onMouseMove])
}
const SomeComponent = () => {
useMouseMove(e => {
// do something with e.clientX and e.clientY
});
}
I have a component where I get repositories like below:
useEffect(() => {
loadRepositories();
}, []);
const loadRepositories = async () => {
const response = await fetch('https://api.github.com/users/mcand/repos');
const data = await response.json();
setUserRepositories(data);
};
return (
<Repository repositories={userRepositories} />
)
The child component only receives the repositories and prints them. It's like that:
const Repository = ({ repositories }) => {
console.log('repository rendering');
console.log(repositories);
const [repos, setRepos] = useState(repositories);
useEffect(() => {
setRepos(repositories);
}, [ ]);
const getRepos = () => {
repos.map((rep, idx) => {
return <div key={idx}>{rep.name}</div>;
});
};
return (
<>
<RepositoryContainer>
<h2>Repos</h2>
{getRepos()}
</>
);
};
export default Repository;
The problem is that, nothing is being displayed. In the console.log I can see that there're repositories, but it seems like the component cannot update itself, I don't know why. Maybe I'm missing something in this useEffect.
Since you're putting the repository data from props into state, then then rendering based on state, when the props change, the state of a Repository doesn't change, so no change is rendered.
The repository data is completely handled by the parent element, so the child shouldn't use any state - just use the prop from the parent. You also need to return from the getRepos function.
const Repository = ({ repositories }) => {
const getRepos = () => {
return repositories.map((rep, idx) => {
return <div key={idx}>{rep.name}</div>;
});
};
return (
<>
<RepositoryContainer>
<h2>Repos</h2>
{getRepos()}
</>
);
};
export default Repository;
You can also simplify
useEffect(() => {
loadRepositories();
}, []);
to
useEffect(loadRepositories, []);
It's not a bug yet, but it could be pretty misleading - your child component is named Repository, yet it renders multiple repositories. It might be less prone to cause confusion if you named it Repositories instead, or have the parent do the .map instead (so that a Repository actually corresponds to one repository array item object).
Change this
useEffect(() => {
setRepos(repositories);
}, [ ]);
to
useEffect(() => {
setRepos(repositories);
}, [repositories]);
In my React-App (create-react-app) I use a selector (created with reselect) to compute derived data from stored data.The Problem is, the selector takes a long time to compute. I would like to show a spinner (or a message) on the user interface. But each time the selector is recomputed the ui freezes.
I read a lot of stuff (Web Worker, requestIdleCallback, requestAnimationFrame) and try to make my own React hook but I am stuck. I cannot use the selector in callbacks.
The searched result is simply to get the ui refreshed before the selector is recomputed.
That's my solution. I don't know if it's "good" or if it breaks some rules of react or reselect, but it works. Maybe you can assess that?The code is simplified to improve readability.
The idea is, the selector returns a Promise and I call requestAnimationFrame before computing the data to get a chance to refresh the ui.
selector.js:
const dataSelector = state => state.data;
export const getDataComputedPromise = createSelector([dataSelector], (data) => {
const compute = function () {
return new Promise((resolve) => {
// heavy computing stuff
resolve(computedData);
});
};
return new Promise((resolve) => {
let start = null;
let requestId = null;
function step (timestamp) {
if (!start) {
start = timestamp;
window.cancelAnimationFrame(requestId);
requestId = window.requestAnimationFrame(step);
return;
};
compute().then(freeResources => {
window.cancelAnimationFrame(requestId);
resolve(freeResources);
});
}
requestId = window.requestAnimationFrame(step);
});
});
myPage.js
const MyPage = ({ someProps }) => {
...
const dataComputedPromise = useSelector(getDataComputedPromise);
const [dataComputed, setDataComputed] = useState([]);
const [computeSelector, setComputeSelector] = useState(false);
useEffect(() => {
setComputeSelector(true);
}, [data]);
useEffect(() => {
dataComputedPromise.then(dataComputed => {
setDataComputed(dataComputed);
setComputeSelector(false);
});
}, [dataComputedPromise]);
...
return <div>
<Loader active={compueSelector}>Computing data...</Loader>
</div>;
};
export default MyPage;
I have a custom hook that keeps a list of toggle states and while I'm seeing the internal state aligning with my expectations, I'm wondering why a component that listens to changes on the state kept by this hook isn't re-rendering on change. The code is as follows
const useToggle = () => {
const reducer = (state, action) => ({...state, ...action});
const [toggled, dispatch] = useReducer(reducer, {});
const setToggle = i => {
let newVal;
if (toggled[i] == null) {
newVal = true;
} else {
newVal = !toggled[i];
}
dispatch({...toggled, [i]: newVal});
console.log('updated toggled state ...', toggled);
};
return {toggled, setToggle};
};
const Boxes = () => {
const {setToggle} = useToggle()
return Array.from({length: 8}, el => null).map((el,i) =>
<input type="checkbox" onClick={() => setToggle(i)}/>)
}
function App() {
const {toggled} = useToggle()
const memoized = useMemo(() => toggled, [toggled])
useEffect(() => {
console.log('toggled state is >>>', toggled) // am not seeing this on console after changes to toggled
}, [toggled])
return (
<div className="App">
<Boxes />
</div>
);
}
It's because you are using useToggle twice.
once in the App
another one in the Boxes.
When you dispatch the action in Boxes, it's updating the toggled instance for Boxes (which is not retrieved in it).
Think of your custom hook like how you use useState. When you use useState, each component gets its own state. Same goes for the custom hook.
So there are a few ways you can address the issue.
Pass the setToggle from App to Boxes via prop-drilling
Use Context API (or Redux or other statement management library to pass
setToggle instance in the App component down)
Here is an example of prop-drilling.
You can follow along
const Boxes = ({ setToggle }) => {
// const { setToggle } = useToggle();
return Array.from({ length: 8 }, el => null).map((el, i) => (
<input key={i} type="checkbox" onClick={() => setToggle(i)} />
));
};
function App() {
const { toggled, setToggle } = useToggle();
useEffect(() => {
console.log("toggled state is >>>", toggled); // am not seeing this on console after changes to toggled
}, [toggled]);
return (
<div className="App">
<Boxes setToggle={setToggle} />
</div>
);
}
Note: that I added key props in Boxes using the index i(and it is a bad practice by the way)
You can see that it's now working as you'd expect.