This is somewhat of a design or react patterns related question but I'm trying to figure out the best way to share sate and methods across different children.
I have a small app where the navigation from step to step and actual form data are rendered and handled in different sibling components. This is a codesandbox of roughly how the app functions.
What I was trying to figure out is the best way to share state between the sibling components. For instance, in the app linked above I need to validate the input from <AppStepOne /> when next is clicked and then move to <AppStepTwo />. Ideally I don't want to just have all the state live in the top level ExampleApp because there are a decent amount of steps and that can get ugly really fast.
The other though I had which I wanted to get some input on what using the react context api. I haven't worked with it before so I wanted to get some idea as if it's something that could possible work as clean solution for this.
Code for app above:
const ExampleApp = () => {
const [currentStep, setCurrentStep] = useState(1);
const getCurrentAppStep = () => {
switch (currentStep) {
case 1:
return {
app: <AppStepOne />,
navigation: (
<AppNavigation onNext={() => setCurrentStep(currentStep + 1)} />
)
};
case 2:
return {
app: <AppStepTwo />,
navigation: (
<AppNavigation onNext={() => setCurrentStep(currentStep + 1)} />
)
};
default:
return {
app: <AppStepOne />,
navigation: (
<AppNavigation onNext={() => setCurrentStep(currentStep + 1)} />
)
};
}
};
const myAppStep = getCurrentAppStep();
return (
<div>
<ParentComp>
<ChildOne>{myAppStep.app}</ChildOne>
<ChildTwo>{myAppStep.navigation}</ChildTwo>
</ParentComp>
</div>
);
};
const ParentComp = ({ children }) => {
return <div>{children}</div>;
};
const ChildOne = ({ children }) => {
return <div>{children}</div>;
};
const ChildTwo = ({ children }) => {
return <div>{children}</div>;
};
const AppStepOne = () => {
const [name, setName] = useState("");
return (
<div>
Name: <input onChange={(e) => setName(e.target.value)} />
</div>
);
};
const AppStepTwo = () => {
const [zipcode, setZipCode] = useState("");
return (
<div>
Zipcode: <input onChange={(e) => setZipCode(e.target.value)} />
</div>
);
};
const AppNavigation = ({ onNext }) => {
return <button onClick={onNext}>Next</button>;
};
Related
What I have is a list that was fetched from an api. This list will be filtered based on the input. But at the first render it will render nothing, unless I press space or add anything to the input. Another solution is set the fetched data to the filteredList. But I don't know if it is the right thing to set the fetched data to two arrays.
import React, { useState, useEffect } from "react";
const PersonDetail = ({ person }) => {
return (
<div>
Id: {person.id} <br />
Name: {person.name} <br />
Phone: {person.phone}
</div>
);
};
const App = () => {
const [personsList, setPersonsList] = useState([]);
const [personObj, setPersonObj] = useState({});
const [showPersonDetail, setShowPersonDetail] = useState(false);
const [newPerson, setNewPerson] = useState("");
const [filter, setFilter] = useState("");
const [filteredList, setFilteredList] = useState(personsList);
useEffect(() => {
fetch("https://jsonplaceholder.typicode.com/users")
.then((response) => response.json())
.then((data) => {
setPersonsList(data);
//setFilteredList(data) <-- I have to add this to work
console.log(data);
});
}, []);
const handleClick = ({ person }) => {
setPersonObj(person);
if (!showPersonDetail) {
setShowPersonDetail(!showPersonDetail);
}
};
const handleChange = (event) => {
setNewPerson(event.target.value);
};
const handleSubmit = (event) => {
event.preventDefault();
const tempPersonObj = {
name: newPerson,
phone: "123-456-7890",
id: personsList.length + 1,
};
setPersonsList((personsList) => [...personsList, tempPersonObj]);
//setFilteredList(personsList) <-- to render the list again when add new person
setNewPerson(" ");
};
const handleFilter = (event) => {
setFilter(event.target.value);
const filteredList =
event.target.value.length > 0
? personsList.filter((person) =>
person.name.toLowerCase().includes(event.target.value.toLowerCase())
)
: personsList;
setFilteredList(filteredList);
};
return (
<div>
<h2>List:</h2>
Filter{" "}
<input value={filter} onChange={handleFilter} placeholder="Enter" />
<ul>
{filteredList.map((person) => {
return (
<li key={person.id}>
{person.name} {""}
<button onClick={() => handleClick({ person })}>View</button>
</li>
);
})}
</ul>
<form onSubmit={handleSubmit}>
<input
placeholder="Add Person"
value={newPerson}
onChange={handleChange}
/>
<button type="submit">Add</button>
</form>
{showPersonDetail && <PersonDetail person={personObj} />}
</div>
);
};
export default App;
Your filtered list is actually something derived from the full persons list.
To express this, you should not create two apparently independent states in this situation.
When your asynchronous fetch completes, the filter is probably already set and you are just setting personsList which is not the list you are rendering. You are rendering filteredList which is still empty and you are not updating it anywhere, except when the filter gets changed.
To avoid all of this, you could create the filtered list on each rendering and — if you think this is not efficient enough — memoize the result.
const filteredList = useMemo(() =>
filter.length > 0
? personsList.filter((person) =>
person.name.toLowerCase().includes(filter.toLowerCase())
)
: personsList,
[filter, personsList]
);
When the filter input gets changed, you should just call setFilter(event.target.value).
This way, you will always have a filtered list, independent of when your asynchronous person list fetching completes or when filters get updated.
Side note: Writing const [filteredList, setFilteredList] = useState(personsList); looks nice but is the same as const [filteredList, setFilteredList] = useState([]); because the initial value will be written to the state only once, at that's when the component gets initialized. At that time personsList is just an empty array.
Is it possible to pass other components through a state? I'm trying to make a tab function like a web browser, and if the user clicks the tab, a component shows up.
In my app.js I have -
const[chosenTab, setChosenTab] = useState("")
return (
<>
<Main chosenTab = {chosenTab}/>
</>
);
In Main.js -
const Main = ({chosenTab}) => {
return (
<>
{chosenTab}
</>
)
}
With the code below, the logic works to display the name of the tab/other component, but doesn't work if I replace {chosenTab} with <{chosenTab}/> to pass it as a component rather than just html.
I don't think this would work as you've structured it - I'd be welcome to have someone prove me wrong though since that would be a neat trick.
Now if I had to solve this problem, I'd simply use a object to hold what I need:
const tabMap = {
"string1": <component1 />,
"string2": <component2 />,
"string3": <component3 />
}
const Main = ({chosenTab}) => {
return (
<>
{tabMap[chosenTab]}
</>
)
}
Even further, let's say you wanted to pass in custom props, you could make tabMap a function to do that.
You can pass component reference itself as a tab.
const TabA = () => <div>Tab A</div>
const TabB = () => <div>Tab B</div>
const Main = ({ ChosenTab }) => {
retur <ChosenTab />
}
const App = () => {
const [chosenTab, setChosenTab] = useState(() => TabA);
const changeTab = (tab) => setChosenTab(() => tab);
return <Main ChosenTab={chosenTab} />
}
export default App;
Or you can store your tabs in object, Map or Array and set state accordingly
const tabs = {
A: TabA,
B: TabB
}
const App = () => {
const [chosenTab, setChosenTab] = useState(() => tabs.A);
const changeTab = (tabKey) => setChosenTab(() => tabs[tabKey]);
return <Main ChosenTab={chosenTab} />
}
export default App;
Probably I'm missing something really simple, but:
I have an array:
const [weight, setWeight] = useState([]);
And I want to map over it to dynamically render a component:
const renderWeight = () => {
weight.map((e) => {
<Weight />;
});
};
I want this to happen when I click on a submit button, and I want the components to render in a specific div.
I can't find a way to do this.
Thank you!
You can use a show variable as toggler to show/hide the weight component like this
import React, { useState } from "react";
const App = () => {
const [weight, setWeight] = useState([1, 2, 3]);
const [show, setShow] = useState(false);
return (
<div className="container">
<div className="weight">{show && weight.map((e) => <Weight />)}</div>
<button onClick={() => setShow(!show)}>Click to show/hide</button>
</div>
);
};
export default App;
I thing you need to return the mapped array
const renderWeight = () => {
return weight.map((e) => {
<Weight />;
});
};
note: Make sure to assign a key to each component rendered
You have to return it.
const [show ,setShow] = useState(false)
const renderWeight = () => {
return weight.map((e) => {
return <Weight />;
});
};
return (
<>
<button onClick={() => setShow(!show)}>Click to show/hide</button>
{
show?
renderWeight():''
}
</>
);
I have a page with the following structure
const Upload = (props) => {
return (
<BaseLayout>
<ToolbarSelection />
<Box>
<FileDropArea />
</Box>
</BaseLayout>
)
}
I have a method which works in the component <FileDropArea />
This is the method used as example
const allSelection = () => {
setFiles((files) =>
files.map((file) => {
file.checked = true;
return file;
})
);
};
In React how can i call this method allSelection from the <ToolbarSelection /> component, where i have my simple button like <Button>All Selection</Button>
You need to use React Context like this:
//create a fileContext.js
const fileContext = React.createContext();
const useFileContext = () => React.useContext(fileContext);
const FileContextProvider = ({ children }) => {
const [files, setFiles] = useState([]);
const allSelection = () => {
setFiles((files) =>
files.map((file) => {
file.checked = true;
return file;
})
);
};
// if you have other methods which may change the files add them here
return (
<fileContext.Provider
value={{
files,
setFiles,
allSelection,
}}
>
{children}
</fileContext.Provider>
);
};
use fileContextProvider in your upload file
const Upload = (props) => {
return (
<FileContextProvider>
<BaseLayout>
<ToolbarSelection />
<Box>
<FileDropArea />
</Box>
</BaseLayout>
</FileContextProvider>
);
};
use it, for example in ToolbarSelection like this:
const ToolbarSelection = () => {
const {files, allSelection} = useFileContext();
// do other stuff
}
React Hooks
I assume you are looking to make the allSelection function reusable. Hooks are a great way to make logic reusable across components.
Create a custom hook useAllSelection. Note that hooks should have a use prefix.
const useAllSelection = (files) => {
const [files, setFiles] = useState([]);
const handleAllSelection = () => {
setFiles((files) =>
files.map((file) => {
file.checked = true;
return file;
})
);
};
return { handleAllSelection };
};
const ToolbarSelection = () => {
// import the hook and use
const { handleAllSelection } = useAllSelection();
return (
<button onClick={handleAllSelection}>All Selection</button>
)
}
ReactJS allows to perform this scenario in a different way. Let me explain it: if you press a button in the ToolbarSelection, pass the value of the new state of that button to FileDropArea as props. Then, in the FileDropArea render, call the method or not depending on the value of that property
const Upload = (props) => {
return (
<BaseLayout>
<ToolbarSelection
onSelectionClick={(value) => setSelected(value)}
/>
<Box>
<FileDropArea
selected = { /* state of a button in the Toolbar */}
/>
</Box>
</BaseLayout>
)
}
Note how the callback in the Toolbar changes the state, and how this new state is passed to FileDropArea as property
I want to pass a variable username from sibling1 component to sibling2 component and display it there.
Sibling1 component:
const sibling1 = ({ usernameData }) => {
// I want to pass the username value I get from input to sibling2 component
const [username, setUsername] = useState("");
const handleChange = event => {
setUsername(event.target.value);
};
return (
<Form.Input
icon='user'
iconPosition='left'
label='Username'
onChange={handleChange}
/>
<Button content='Login' onClick={handleClick} />
)
}
export default sibling1;
Sibling2 component:
export default function sibling2() {
return (
<h1> Here is where i want to display it </h1>
)
}
You will need to handle your userName in the parent of your siblings. then you can just pass setUsername to your sibling1, and userName to your sibling2. When sibling1 use setUsername, it will update your parent state and re-render your sibling2 (Because the prop is edited).
Here what it looks like :
const App = () => {
const [username, setUsername] = useState('Default username');
return (
<>
<Sibling1 setUsername={setUsername} />
<Sibling2 username={username} />
</>
)
}
const Sibling2 = ({username}) => {
return <h1> Helo {username}</h1>;
}
const Sibling1 = ({setUsername}) => {
return <button onClick={setUsername}>Set username</button>;
}
In parent of these two components create a context where you will store a value and value setter (the best would be from useState). So, it will look like this:
export const Context = React.createContext({ value: null, setValue: () => {} });
export const ParentComponent = () => {
const [value, setValue] = useState(null);
return (
<Context.Provider value={{value, setValue}}>
<Sibling1 />
<Sibling2 />
</Context.Provider>
);
Then in siblings you are using it like this:
const Sibling1 = () => {
const {setValue} = useContext(Context);
const handleChange = event => {
setValue(event.target.value);
};
// rest of code here
}
const Sibling2 = () => {
const {value} = useContext(Context);
return <h1>{value}</h1>;
}
best way: React Context + hooks
you can use React Context. take a look at this example:
https://codesandbox.io/s/react-context-api-example-0ghhy