I wanna make follow/unfollow toggle button, and following / follower list(object in array) will be called seperately from server.
Follower list needs to have both unfollow/follow button status.
When I call follower list, how can I check the IDs of the people who follow me matches the IDs of my following list & reflect in on the button?
example following, follower object in array
[{id: 1, profileImg: xxx},{id: 2, profileImg: xxx},{id: 3, profileImg: xxx}... ]
my code in js below
const { select } = props;
const [choice, setChoice] = useState(select);
const [followingList, setFollowingList] = useState([]);
const [followerList, setFollowerList] = useState([]);
const handleChoice = (e) => {
setChoice(e.target.value);
};
useEffect(() => {
getFollowing()
.then((res) => {
setFollowingList(res);
})
.then(
getFollower().then((res) => {
setFollowerList(res);
}),
);
}, []);
my code in html
<Container onClick={(e) => e.stopPropagation()}>
<TogglebtnContainer>
<ToggleBtn onClick={handleChoice} value="following" choice{choice}>Following</ToggleBtn>
<ToggleBtn onClick={handleChoice} value="follower" choice={choice}>Follower</ToggleBtn>
</TogglebtnContainer>
<FollowContainer>
<Follow>
{choice === 'following'? (followingList.map((follow, idx) => {
return (
<div className="follow-item" key={idx}>
<div className="follow-img"><img src={follow.profileImg} alt="UserPic" /> </div>
<div className="follow-name">{follow.nickname}</div>
<FollowBtn key={follow.id}>Unfollow</FollowBtn></div>
);})
: (followerList.map((follow, idx) => {
return (
<div className="follow-item" key={idx}>
<div className="follow-img">
<img src={follow.profileImg} alt="UserPic" />
</div>
<div className="follow-name">{follow.nickname}</div>
<FollowBtn key={follow.id}>follow</FollowBtn>
</div>
})}
</Follow>
</FollowContainer>
</Container>
I thought I could check if this IDs matches IDs of my following list and create a new boolean state.
(ex [isFollowing, setIsFollowing = useState(false)) but couldn't find a way.
getFollower().then((res) => {
setFollowerList(res);
To know which followers the user is already following and follow/unfollow followers
short answer, set a flag when loading the data
useEffect(() => {
let isValidScope = true;
const fetchData = async () => {
const followingList = await getFollowing();
if (!isValidScope) { return; }
setFollowingList(followingList);
let followersList = await getFollower();
if (!isValidScope) { return; }
const followingUserIds = followingList?.map(f => f.id)
followersList = followersList?.map(follower => {
return followingUserIds?.includes(follower.id) ?
{ ...follower, isFollowing: true } : follower
}
setFollowerList(followersList)
}
fetchData()
return () => { isValidScope = false }
}, []);
const onFollowFollower = (followerId) => {
const followersList = followerList?.map(follower => {
return follower.id === followerId ?
{ ...follower, isFollowing: true } : follower
}
setFollowerList(followersList)
}
const onUnfollowFollower = (followerId) => {
const followersList = followerList?.map(follower => {
return follower.id === followerId ?
{ ...follower, isFollowing: false } : follower
}
setFollowerList(followersList)
}
Render code
<Follow>
{choice === 'following'? (followingList.map((follow, idx) => {
return (
<div className="follow-item" key={idx}>
<div className="follow-img"><img src={follow.profileImg} alt="UserPic" /> </div>
<div className="follow-name">{follow.nickname}</div>
<FollowBtn key={follow.id}>Unfollow</FollowBtn>
</div>
);})
: (followerList.map((follow, idx) => {
return (
<div className="follow-item" key={idx}>
<div className="follow-img">
<img src={follow.profileImg} alt="UserPic" />
</div>
<div className="follow-name">{follow.nickname}</div>
{ follow?.isFollowing ? <FollowBtn () => onUnfollowFollower(follow.id)>Unfollow</FollowBtn> : null }
{ !follow?.isFollowing ? <FollowBtn onClick={() => onFollowFollower(follow.id)>Follow</FollowBtn> : null }
</div>
})}
</Follow>
You can read about working with list in the new React docs
if you are refetching the follower and following list on every change it will be better to recalculate the followers list using a useMemo on every change
Hope this helps you in someway
I am getting an error from strapi backend data when I fetch particular data into the front end react app I get an error when I log the data into the browser console I see my data in the browser console.
query GetPromoProducts {
allStrapiProduct(filter: {promo: {eq: true}}) {
edges {
node {
strapiId
name
variants {
images {
url
}
}
}
}
}
}
`)
const [selectedSlides, setSelectedSlides] = useState(0)
console.log(data);
var slides = [];
data.allStrapiProduct.edges.map(({node}) => {
console.log(node.variants[0].images[0]);
})
Debugging
To debug the server side, use optional chaining and console.log to work your way up to the object's that returning null.
Not sure what the exact code looks like, based on question.
const myQuery = graphql`
query GetPromoProducts {
allStrapiProduct(filter: { promo: { eq: true } }) {
edges {
node {
strapiId
name
variants {
images {
url
}
}
}
}
}
}
`;
const Component = () => {
const [selectedSlides, setSelectedSlides] = useState(0);
console.log(data);
data.allStrapiProduct.edges.map(({ node }) => {
// For this case, use optional chaining to work your way up the tree
console.log(node);
console.log(node?.variants);
console.log(node?.variants?.[0]);
console.log(node?.variants?.[0]?.images);
console.log(node?.variants?.[0]?.images?.[0]);
});
};
To stop right at the area this happens:
data.allStrapiProduct.edges.map(({ node }) => {
if (!node?.variants?.[0]?.images?.length) {
console.log(node);
console.log(node?.variants);
console.log(node?.variants?.[0]);
console.log(node?.variants?.[0]?.images);
console.log(node?.variants?.[0]?.images?.[0]);
throw "Required data missing";
}
});
Resilient React with GraphQL
GraphQL structured data may be typed, but unless the fields are required, you have to handle null.
To make the client-side code more robust, you can use Array.prototype.filter() to skip objects with no images, or - as in this example - make components handle the case where data is missing. It's entirely up to how you want the frontend app to render it.
I haven't tested this code, so take it as "pseudo-JSX" to demonstrate handling empty graphql response fields.
const ProductVariant = ({ variant }) => {
if (!variant) return null;
return (
<div className="variant">
{variant?.images?.map?.((image, idx) => (
<img src={url} key={idx} />
))}
</div>
);
};
const ProductVariants = ({ variants }) => {
if (!variants?.length > 0) return null;
return (
<div className="variant-list">
<div>Variants</div>
<div className="variant-list--items">
{variants?.map?.((variant, idx) => (
<ProductVariant variant={variant} key={idx} />
))}
</div>
</div>
);
};
const Products = () => {
const [selectedSlides, setSelectedSlides] = useState(0);
console.log(data);
const products = data.allStrapiProduct.edges.map(({ node }) => {
// Handle as you deem fit
});
return (
<div id="products">
<p>Here is a list of products</p>
<div className="products">
{products?.map?.((product, idx) => {
return (
<div className="product" key={idx}>
{product?.variants?.length > 1 && (
<ProductVariants variants={variants} />
)}
</div>
);
})}
</div>
</div>
);
};
Here is the original example of group checkbox of antd that I need and its fine:
const plainOptions = ['Apple', 'Pear', 'Orange'];
const defaultCheckedList = ['Apple', 'Orange'];
class App extends React.Component {
state = {
checkedList: defaultCheckedList,
indeterminate: true,
checkAll: false,
};
onChange = checkedList => {
this.setState({
checkedList,
indeterminate: !!checkedList.length && checkedList.length < plainOptions.length,
checkAll: checkedList.length === plainOptions.length,
});
};
onCheckAllChange = e => {
this.setState({
checkedList: e.target.checked ? plainOptions : [],
indeterminate: false,
checkAll: e.target.checked,
});
};
render() {
return (
<div>
<div style={{ borderBottom: '1px solid #E9E9E9' }}>
<Checkbox
indeterminate={this.state.indeterminate}
onChange={this.onCheckAllChange}
checked={this.state.checkAll}
>
Check all
</Checkbox>
</div>
<br />
<CheckboxGroup
options={plainOptions}
value={this.state.checkedList}
onChange={this.onChange}
/>
</div>
);
}
}
My question is how can I replace the plainOptions and defaultCheckedList by object array instead of simple array and using attribute name for this check boxes?
For example this object:
const plainOptions = [
{name:'alex', id:1},
{name:'milo', id:2},
{name:'saimon', id:3}
];
const defaultCheckedList = [
{name:'alex', id:1},
{name:'milo', id:2}
];
I want to use attribute name as the key in this example.
Problem solved. I should use "Use with grid" type of group checkbox. It accepts object array. The only think I could do was creating a function that inject "label" and "value" to my object. It makes some duplicates but no problem.
function groupeCheckboxify(obj, labelFrom) {
for (var i = 0; i < obj.length; i++) {
if (obj[i][labelFrom]) {
obj[i]['label'] = obj[i][labelFrom];
obj[i]['value'] = obj[i][labelFrom];
}
if (i == obj.length - 1) {
return obj;
}
}
}
// for calling it:
groupeCheckboxify( myObject , 'name');
I'd this same problem and couldn't find any answer on the entire web. But I tried to find a good way to handle it manually.
You can use this code:
import { Checkbox, Dropdown } from 'antd';
const CheckboxGroup = Checkbox.Group;
function CheckboxSelect({
title,
items,
initSelectedItems,
hasCheckAllAction,
}) {
const [checkedList, setCheckedList] = useState(initSelectedItems || []);
const [indeterminate, setIndeterminate] = useState(true);
const [checkAll, setCheckAll] = useState(false);
const onCheckAllChange = (e) => {
setCheckedList(e.target.checked ? items : []);
setIndeterminate(false);
setCheckAll(e.target.checked);
};
const onChangeGroup = (list) => {
if (hasCheckAllAction) {
setIndeterminate(!!list.length && list.length < items.length);
setCheckAll(list.length === items.length);
}
};
const updateItems = (el) => {
let newList = [];
if (el.target.checked) {
newList = [...checkedList, el.target.value];
} else {
newList = checkedList.filter(
(listItem) => listItem.id !== el.target.value.id,
);
}
setCheckedList(newList);
};
useEffect(() => {
setCheckedList(initSelectedItems);
}, []);
const renderItems = () => {
return (
<div classname="items-wrapper">
{hasCheckAllAction ? (
<Checkbox
indeterminate={indeterminate}
onChange={onCheckAllChange}
checked={checkAll}
>
All
</Checkbox>
) : null}
<CheckboxGroup onChange={onChangeGroup} value={checkedList}>
<>
{items.map((item) => (
<Checkbox
key={item.id}
value={item}
onChange={($event) => updateItems($event)}
>
{item.name}
</Checkbox>
))}
</>
</CheckboxGroup>
</div>
);
};
return (
<Dropdown overlay={renderItems()} trigger={['click']}>
<div>
<span className="icon icon-arrow-down" />
<span className="title">{title}</span>
</div>
</Dropdown>
);
}
It looks like the only difference you are talking about making is using an array of objects instead of strings? If that's the case, when looping through the array to create the checkboxes, you access the object attributes using dot notation. It should look something like this if I understand the problem correctly.
From CheckboxGroup component:
this.props.options.forEach(el => {
let name = el.name;
let id = el.id;
//rest of code to create checkboxes
or to show an example in creating components
let checkboxMarkup = [];
checkboxMarkup.push(
<input type="checkbox" id={el.id} name={el.name} key={`${el.id} - ${el.name}`}/>
);
}
'el' in this case refers to each individual object when looping through the array. It's not necessary to assign it to a variable, I just used that to show an example of how to access the properties.
Can't manage to make useRef/createRef to get any other div's other then what was added last. How can i make it so when the button is clicked the ref to the div changes.
I've tried with both useRef and createRef. Since I want to make a new instance of ref, i've looked more into createRef rather then useRef.
I've also played around useEffect. But my solution didn't help me with my biggest problem
I have made a small project containing 3 components to help you understand what I'm trying to explain.
I also have a database containing mock data -> in my real project this isn't the problem. It's an array containing objects.
[{'id':'1', 'name':'first'},...]
Main:
const MainComponent = () => {
const dataRef = React.createRef(null)
React.useEffect (() => {
if(dataRef && dataRef.current){
dataRef.current.scrollIntoView({ behavior:'smooth', block:'start' })
}
},[dataRef])
const _onClick = (e) => {
dataRef.current.focus();
}
return(
<>
{data && data.map((entry, index) =>{
return <ButtonList
key={index}
entry={entry}
onClick={_onClick}
/>
})}
{data && data.map((entry, index) =>{
return <ListingAllData
key={index}
dataRef={dataRef}
entry={entry}
index={index}/>
})}
</>
)
}
Button Component
const ButtonList = ({ entry, onClick }) => {
return <button onClick={onClick}>{entry.name}</button>
}
Listing data component
const ListingAllData = (props) => {
const {entry, dataRef } = props;
return (
<div ref={dataRef}>
<p>{entry.id}</p>
<p>{entry.name}</p>
</div>
);
}
I've console logged the data.current, it only fetches the last element. I hoped it would fetch the one for the button I clicked on.
I think the main idea here is to create dynamic refs for each element (array of refs), that's why only the last one is selected when app renders out.
const MainComponent = () => {
const dataRefs = [];
data.forEach(_ => {
dataRefs.push(React.createRef(null));
});
const _onClick = (e, index) => {
dataRefs[index].current.focus();
dataRefs[index].current.scrollIntoView({
behavior: "smooth",
block: "start"
});
};
return (
<>
{data &&
data.map((entry, index) => {
return (
<ButtonList
key={index}
entry={entry}
onClick={e => _onClick(e, index)}
/>
);
})}
{data &&
data.map((entry, index) => {
return (
<>
<ListingAllData
key={index}
dataRef={dataRefs[index]}
entry={entry}
index={index}
/>
</>
);
})}
</>
);
};
Created working example in code sandbox.
https://codesandbox.io/s/dynamic-refs-so25v
Thanks to Janiis for the answer, my solution was:
in MainComponent
...
const refs = data.reduce((acc, value) => {
acc[value.id] = React.createRef();
return entry;
}, {});
const _onClick = id => {
refs[id].current.scrollIntoView({
behavior: 'smooth',
block: 'start'
});
}
....
then i passed it through to the child and referred like
<div ref={refs[entry.id]}>
I have a React component, and inside the render method of the component I have something like this:
render() {
return (
<div>
<div>
// removed for brevity
</div>
{ switch(...) {} }
<div>
// removed for brevity
</div>
</div>
);
}
Now the point is that I have two div elements, one at the top and one at the bottom, that are fixed. In the middle I want to have a switch statement, and according to a value in my state I want to render a different component. So basically, I want the two div elements to be fixed always, and just in the middle to render a different component each time. I'm using this to implement a multi-step payment procedure). Though, as is the code currently it doesn't work, as it gives me an error saying that switch is unexpected. Any ideas how to achieve what I want?
Try this, which is way cleaner too: Get that switch out of the render in a function and just call it passing the params you want. For example:
renderSwitch(param) {
switch(param) {
case 'foo':
return 'bar';
default:
return 'foo';
}
}
render() {
return (
<div>
<div>
// removed for brevity
</div>
{this.renderSwitch(param)}
<div>
// removed for brevity
</div>
</div>
);
}
In contrast to other answers, I would prefer to inline the "switch" in the render function. It makes it more clear what components can be rendered at that position. You can implement a switch-like expression by using a plain old javascript object:
render () {
return (
<div>
<div>
{/* removed for brevity */}
</div>
{
{
'foo': <Foo />,
'bar': <Bar />
}[param]
}
<div>
{/* removed for brevity */}
</div>
</div>
)
}
That's happening, because switch statement is a statement, but here javascript expects an expression.
Although, it's not recommended to use switch statement in a render method, you can use self-invoking function to achieve this:
render() {
// Don't forget to return a value in a switch statement
return (
<div>
{(() => {
switch(...) {}
})()}
</div>
);
}
I did this inside the render() method:
render() {
const project = () => {
switch(this.projectName) {
case "one": return <ComponentA />;
case "two": return <ComponentB />;
case "three": return <ComponentC />;
case "four": return <ComponentD />;
default: return <h1>No project match</h1>
}
}
return (
<div>{ project() }</div>
)
}
I tried to keep the render() return clean, so I put my logic in a 'const' function right above. This way I can also indent my switch cases neatly.
I'm not a big fan of any of the current answers, because they are either too verbose, or require you to jump around the code to understand what is going on.
I prefer doing this in a more react component centred way, by creating a <Switch/>. The job of this component is to take a prop, and only render children whose child prop matches this one. So in the example below I have created a test prop on the switch, and compared it to a value prop on the children, only rendering the ones that match.
Example:
const Switch = props => {
const { test, children } = props
// filter out only children with a matching prop
return children.find(child => {
return child.props.value === test
})
}
const Sample = props => {
const someTest = true
return (
<Switch test={someTest}>
<div value={false}>Will display if someTest is false</div>
<div value={true}>Will display if someTest is true</div>
</Switch>
)
}
ReactDOM.render(
<Sample/>,
document.getElementById("react")
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="react"></div>
You can make the switch as simple or as complex as you want. Don't forget to perform more robust checking of the children and their value props.
A way to represent a kind of switch in a render block, using conditional operators:
{(someVar === 1 &&
<SomeContent/>)
|| (someVar === 2 &&
<SomeOtherContent />)
|| (this.props.someProp === "something" &&
<YetSomeOtherContent />)
|| (this.props.someProp === "foo" && this.props.someOtherProp === "bar" &&
<OtherContentAgain />)
||
<SomeDefaultContent />
}
It should be ensured that the conditions strictly return a boolean.
lenkan's answer is a great solution.
<div>
{{ beep: <div>Beep</div>,
boop: <div>Boop</div>
}[greeting]}
</div>
If you need a default value, then you can even do
<div>
{{ beep: <div>Beep</div>,
boop: <div>Boop</div>
}[greeting] || <div>Hello world</div>}
</div>
Alternatively, if that doesn't read well to you, then you can do something like
<div>
{
rswitch(greeting, {
beep: <div>Beep</div>,
boop: <div>Boop</div>,
default: <div>Hello world</div>
})
}
</div>
with
function rswitch (param, cases) {
if (cases[param]) {
return cases[param]
} else {
return cases.default
}
}
Although this is yet another way to do it, if you have gone all-in on hooks, you could take advantage of useCallback to produce a function that is only recreated when necessary.
Let's say you have a component which should be rendered according to a status prop. With hooks, you could implement this as follows:
const MyComponent = ({ status }) => {
const renderContent = React.useCallback(() => {
switch(status) {
case 'CONNECTING':
return <p className="connecting">Connecting...</p>;
case 'CONNECTED':
return <p className="success">Connected Successfully!</p>
default:
return null;
}
}, [status]);
return (
<div className="container">
{renderContent()}
</div>
);
};
I like this because:
It's obvious what is going on - a function is created, and then later called (the immediately invoked anonymous function method looks a little odd, and can potentially confuse newer developers)
The useCallback hook ensures that the renderContent callback is reused between renders, unless the depedency status changes
The renderContent function uses a closure to access the necessary props passed in to the component. A separate function (like the accepted answer) requires the passing of the props into it, which can be burdensome (especially when using TypeScript, as the parameters should also be typed correctly)
You can do something like this.
<div>
{ object.map((item, index) => this.getComponent(item, index)) }
</div>
getComponent(item, index) {
switch (item.type) {
case '1':
return <Comp1/>
case '2':
return <Comp2/>
case '3':
return <Comp3 />
}
}
function Notification({ text, status }) {
return (
<div>
{(() => {
switch (status) {
case 'info':
return <Info text={text} />;
case 'warning':
return <Warning text={text} />;
case 'error':
return <Error text={text} />;
default:
return null;
}
})()}
</div>
);
}
You can't have a switch in render. The psuedo-switch approach of placing an object-literal that accesses one element isn't ideal because it causes all views to process and that can result in dependency errors of props that don't exist in that state.
Here's a nice clean way to do it that doesn't require each view to render in advance:
render () {
const viewState = this.getViewState();
return (
<div>
{viewState === ViewState.NO_RESULTS && this.renderNoResults()}
{viewState === ViewState.LIST_RESULTS && this.renderResults()}
{viewState === ViewState.SUCCESS_DONE && this.renderCompleted()}
</div>
)
If your conditions for which view state are based on more than a simple property – like multiple conditions per line, then an enum and a getViewState function to encapsulate the conditions is a nice way to separate this conditional logic and cleanup your render.
I really liked the suggestion in https://stackoverflow.com/a/60313570/770134, so I adapted it to Typescript like so
import React, { FunctionComponent } from 'react'
import { Optional } from "typescript-optional";
const { ofNullable } = Optional
interface SwitchProps {
test: string
defaultComponent: JSX.Element
}
export const Switch: FunctionComponent<SwitchProps> = (props) => {
return ofNullable(props.children)
.map((children) => {
return ofNullable((children as JSX.Element[]).find((child) => child.props['value'] === props.test))
.orElse(props.defaultComponent)
})
.orElseThrow(() => new Error('Children are required for a switch component'))
}
const Foo = ({ value = "foo" }) => <div>foo</div>;
const Bar = ({ value = "bar" }) => <div>bar</div>;
const value = "foo";
const SwitchExample = <Switch test={value} defaultComponent={<div />}>
<Foo />
<Bar />
</Switch>;
import React from 'react';
import ListView from './ListView';
import TableView from './TableView';
function DataView({
currView,
data,
onSelect,
onChangeStatus,
viewTodo,
editTodo,
deleteTodo,
}) {
return (
<div>
{(function () {
switch (currView) {
case 'table':
return (
<TableView
todos={data}
onSelect={onSelect}
onChangeStatus={onChangeStatus}
viewTodo={viewTodo}
editTodo={editTodo}
deleteTodo={deleteTodo}
/>
);
case 'list':
return (
<ListView
todos={data}
onSelect={onSelect}
onChangeStatus={onChangeStatus}
viewTodo={viewTodo}
editTodo={editTodo}
deleteTodo={deleteTodo}
/>
);
default:
break;
}
})()}
</div>
);
}
export default DataView;
Improved a bit from
Matt Way's answer.
export const Switch = ({ test, children }) => {
const defaultResult = children.find((child) => child.props.default) || null;
const result = children.find((child) => child.props.value === test);
return result || defaultResult;
};
export const Case = ({ children }) => children;
const color = getColorFromTheMostComplexFnEver();
<Switch test={color}>
<Case value="Green">Forest</Case>
<Case value="Red">Blood</Case>
<Case default>Predator</Case>
</Switch>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
How about:
mySwitchFunction = (param) => {
switch (param) {
case 'A':
return ([
<div />,
]);
// etc...
}
}
render() {
return (
<div>
<div>
// removed for brevity
</div>
{ this.mySwitchFunction(param) }
<div>
// removed for brevity
</div>
</div>
);
}
Switch-Case statement within React Component could be used as follows:
<div id="time-list">
{
(() => {
switch (groupByFilterId) {
case 0:/*Case 0 */
return (
<div>Case 0</div>
)
break;
case 1: /*Case 1 */
return (
<div>Case 1</div>
)
break;
case 2:/*Case 2 */
return (
<div>Case 2</div>
)
break;
}
})()}
</div>
make it easy and just use many if statements.
for example:
<Grid>
{yourVar==="val1"&&(<> your code for val1 </>)}
{yourVar==="val2"&&(<> your code for val2 </>)}
.... other statments
</Grid>
I converted accepted answer to arrow functional component solution and saw James provides similar answer and one can get error not defined. So here is the solution:
const renderSwitch = (param) => {
switch (param) {
case "foo":
return "bar";
default:
return "foo";
}
};
return (
<div>
<div></div>
{renderSwitch(param)}
<div></div>
</div>
);
Here is a full working example using a button to switch between components
you can set a constructor as following
constructor(props)
{
super(props);
this.state={
currentView: ''
}
}
then you can render components as following
render()
{
const switchView = () => {
switch(this.state.currentView)
{
case "settings": return <h2>settings</h2>;
case "dashboard": return <h2>dashboard</h2>;
default: return <h2>dashboard</h2>
}
}
return (
<div>
<button onClick={(e) => this.setState({currentView: "settings"})}>settings</button>
<button onClick={(e) => this.setState({currentView: "dashboard"})}>dashboard</button>
<div className="container">
{ switchView() }
</div>
</div>
);
}
}
As you can see I am using a button to switch between states.
I know I'm a bit late to the party, but I think this implementation might help
You can render the components using conditional operators instead
If you had the following switch statement
switch(value) {
case CASE1:
return <Case1Component/>
case CASE2:
return <Case2Component/>
case CASE3:
return <Case3Component/>
default:
return <DefaultComponent/>
}
You can convert it to react component like so
const cases = [CASE0, CASE1, CASE2]
// Reminds me of 'react-router-dom'
return (
<div>
{value === cases[0] && <Case0Component/>}
{value === cases[1] && <Case1Component/>}
{value === cases[2] && <Case2Component/>}
{!cases.includes(value) && <DefaultComponent/>}
</div>
)
I am using this helper that allows me to have switch statements in JSX
// in helpers folder
const switchTrue = (object) => {
const { default: defaultValue, ...rest } = object;
const obj = { default: defaultValue, ...rest };
const result = Object.keys(obj).reduce((acc, cur) => {
return {
...acc,
[cur === 'default' ? 'true' : cur]: obj[cur],
};
}, {});
return result['true'];
};
const Sample = () => {
const isDataLoading = false;
return (
<div>
{
switchTrue({
[`${isDataLoading}`]: <div>Loading</div>,
[`${!isDataLoading}`]: <div>Data Ready</div>,
default: <div>Default</div>,
})
}
</div>
)
}
ReactDOM.render(
<Sample/>,
document.getElementById("react")
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="react"></div>
This helper should do the trick.
Example Usage:
{componentSwitch(3, (switcher => switcher
.case(1, () =>
<p>It is one</p>
)
.case(2, () =>
<p>It is two</p>
)
.default(() =>
<p>It is something different</p>
)
))}
Helper:
interface SwitchCases<T> {
case: (value: T, result: () => React.ReactNode) => SwitchCases<T>;
default: (result: () => React.ReactNode) => SwitchCases<T>;
}
export function componentSwitch<T>(value: T, cases: (cases: SwitchCases<T>) => void) {
var possibleCases: { value: T, result: () => React.ReactNode }[] = [];
var defaultResult: (() => React.ReactNode) | null = null;
var getSwitchCases: () => SwitchCases<T> = () => ({
case: (value: T, result: () => React.ReactNode) => {
possibleCases.push({ value: value, result });
return getSwitchCases();
},
default: (result: () => React.ReactNode) => {
defaultResult = result;
return getSwitchCases();
},
})
// getSwitchCases is recursive and will add all possible cases to the possibleCases array and sets defaultResult.
cases(getSwitchCases());
// Check if one of the cases is met
for(const possibleCase of possibleCases) {
if (possibleCase.value === value) {
return possibleCase.result();
}
}
// Check if the default case is defined
if (defaultResult) {
// Typescript wrongly assumes that defaultResult is always null.
var fixedDefaultResult = defaultResult as (() => React.ReactNode);
return fixedDefaultResult();
}
// None of the cases were met and default was not defined.
return undefined;
}
We can do this directly using useCallback
const renderContent = useCallback(() => {
switch (sortState) {
case 'one':
return 'ONE';
case 'two':
return 'TWO';
case 'three':
return 'THREE';
case 'four':
return 'FOUR';
default:
return 'ONE';
}
}, [sortState]);
This is to be used inside the jsx
<div>Sort:{renderContent()}</div>
This answer is specifically intended to address this "duplicate" question, by #tonyfat, regarding how to use conditional expressions to handle the same task.
Avoiding statements here seems like more trouble than it's worth, but this script does the job as the snippet demonstrates:
// Runs tests
let id = 0, flag = 0;
renderByFlag(id, flag); // jobId out of range
id = 1; // jobId in range
while(++flag < 5){ // active flag ranges from 1 to 4
renderByFlag(id, flag);
}
// Defines a function that chooses what to render based on two provided values
function renderByFlag(jobId, activeFlag){
jobId === 1 ? (
activeFlag === 1
? render("A (flag = 1)")
: activeFlag === 2
? render("B (flag = 2)")
: activeFlag === 3
? render("C (flag = 3)")
: pass(`flag ${activeFlag} out of range`)
)
: pass(`jobId ${jobId} out of range`)
}
// Defines logging functions for demo purposes
function render(val){ console.log(`Rendering ${val}`); }
function pass(reason){ console.log(`Doing nothing (${reason})`) }
const [route, setRoute] = useState(INITIAL_ROUTE)
return (
<RouteContext.Provider value={{ route, setRoute }}>
{(() => {
switch (route) {
case Route.Home:
return <PopupHomePage />
case Route.App:
return <PopupAppPage />
default:
return null
}
})()}
</RouteContext.Provider>
This is another approach.
render() {
return {this[`renderStep${this.state.step}`]()}
renderStep0() { return 'step 0' }
renderStep1() { return 'step 1' }