Can anyone point a direction of the Component syntax using the latest React-Native init cmd? I don't recall ES6 class syntax quite like it.
export default class App extends Component<{}> {
}
Where, I've seen the following without brackets.
export default class App extends Component {
}
Thanks
Reference : https://reactjs.org/docs/components-and-props.html
class Example extends Component {
render() {
return <h1>Hello</h1>;
}
}
This is the ES6 way of defining components in react.
Related
I would like to pass my object based on JavaScript class from mixin to component without reactivity. I use TypeScript, so I can't set the object to this of mixin without setting types in data(). But data() reactivity breaks some thing in my object.
mixin.js:
export default {
setup() {
const foo = new Foo()
return {
foo,
}
}
}
component.js:
import mixin from './mixin.js'
export default {
setup() {
// How can I get foo here?
}
}
Update 1
Yes, it is good solution for using only one foo instance for everywhere.
But how can I use different foo instances for each component?
Same as in JS classes:
class Mixin {
foo() {
// ...
}
}
class Component extends Mixin {
bar() {
this.foo()
}
}
mixin.js
export const foo = new Foo()
Import (and use) foo anywhere in your app, including any setup() function:
import { foo } from './path/to/mixin'
The above uses the same instance everywhere. If you want to use different instances of foo in each separate component, mixin.js:
export const useFoo = () => new Foo()
Anywhere else:
import { useFoo } from './path/to/mixin'
const foo = useFoo()
However, take note the second approach creates a new intance of Foo() every time useFoo() is called. So once you called it, you must use foo in that component.
Calling useFoo() multiple times in the same component will generate multiple instances, unlike how you'd use useStore(), for example.
But, I'm wondering, why do you need a mixin in the first place? Why not use:
const foo = new Foo()
...in the components where you need it?
What are you trying to achieve? And, more importantly, why?
In App.js I have some thing like
Class App extends Component {
constructor(props){
super(props)
global.test = NativeModules.TestClass
}
}
And in Test class I am using it like
Class Test extends Component {
constructor(props){
super(props)
global.test.testFunction("Testing")
}
}
So how to mock global.test.testFunction for the above class
I suggest another approach for global function, variables. You can create a Utils class for each global functions, variables (constants or enums) and import the Utils wherever you need to use them.
Here is a very basic example for Utils Class:
Utils Class
export default class Utils {
static navigationRef = null;
static showAlert(title, desc) {
Alert.alert(title, desc);
}
}
USAGE:
import Utils from "./shared/utils"
// Example of static function
Utils.showAlert("Hello" "Alert Description")
// Example of static variable
Utils.navigationRef = this.props.navigation;
I created a class in react native.
import Author from "./authorDetails";
class MainFeedPost {
id;
description;
postImage;
author;
creationDateTime;
version;
status;
extra = {
likes,
shares,
comments
};
constructor() {
this.author = new Author();
}
}
export default MainFeedPost;
Now I want to set this as a type in one of my components state. I tried it like this an it is undefined.
import { MainFeedPost } from "../../models";
class SharePostScreen extends Component {
constructor(props) {
super(props);
this.state = {
post: MainFeedPost
};
}
doesn't this support in react native? I want to initialize the shape of my object with MainFeedPost class.
You told "as a type". If you want static type checking, you need something like flow.
If you wanna value in the state, you must place there an instance:
...
this.state = {
post: new MainFeedPost(),
};
...
UPD:
I got your point. Because of default export you need to use import MainFeedPost from "...", without braces.
I had this working in a react-native app, but I feel I had to do some stuff with babel and I can't remember what it was. For whatever reason this is not working, it's saying cannot read property CONSTANT_1 of undefined.
export default class Main extends React.Component {
static MyClassProp = {
CONSTANT_1: 1,
CONSTANT_2: 2
};
static defaultProps = {
prop1: Main.MyClassProp.CONSTANT_1
};
...
}
Can anybody tell me if I'm supposed to include something in a .babelrc or package.json to get this to compile correctly?
I have a class Two with a bunch of functions inside. Some of them are using this.setState({}) and they throw me a warning: setState(...): Can only update a mounted or mounting component.
Here's an example of the code:
class One extends React.Component {
constructor() {
super()
this.two = new Two;
}
componentDidMount() {
this.two.hello()
}
render() {
return (<View><Text>Hello World!</Text></View>)
}
}
class Two extends React.Component {
constructor() {
super()
this.state = {
connected: false
}
}
hello() {
this.setState({connected: true}) //This one throw the warning
}
}
Is there any way to do things in a better way? Since my class Two is functionnal, I would like to not change the code too much to have things working. Btw, I need to the this.two = new Two line.
Should I create a library, a module, or whatever? If so, can you give me a good tutorial?
If you are not mounting the Component, React can’t update it’s state using it’s built-in state handler.
And since you are not mounting it, it should probably not be a react component at all. Try using a regular class instead:
class Two {
constructor() {
super()
this.state = {
connected: false
}
}
hello() {
this.state.connected = true
}
}
The main problem here is you are trying to make components in React communicate in an unconventional way.
The way you want to go about this is to make use of props. This is how components talk to each other in React, instead of being direct, like you're attempting.
Check out my code here where I'm doing the same as you
Basically, I've written 2 examples in 1 here. The first is passing just raw data through to another component. (this.props.data.someData). And the second, which is more like what you're wanting to do, is using React's Life Cycle methods, to listen for when a function should run, through prop activation.
What this means in my example, is when the runFunction prop is passed into Two, either when it's first created componentDidMount() or when set to true later componentWillRecieveProps(), it will run the testFunction()