如何从另一个类 React-native 调用函数

Question

I am trying to call a function from another class it throws an error getValue is not a function. i dont want to use static. I hope there's a solution for it. here's my code

import React, { Component } from "react";
import SecondClass from "./main"

export default class A extends Component{
  constructor (props) {  
    super(props)

 onPress = ()=>{
   getValue()

 }
}

//SecondClass
export default class SecondClass extends Component{
  constructor (props) {  
    super(props)
  }
  getValues = () => {
    alert("Hello")
  }   
}

Answer 1

我认为您需要在A定义函数，然后将SecondClass组件中的函数作为道具传递...

Answer 2

https://www.npmjs.com/package/react-native-simple-events

You can use this library here you can register your function and can trigger from anywhere in app.

For register your function use on("eventID", "listenerID", ()=>{//call getValues}) in class SecondClass

For Trigger your function use trigger("eventID", eventData) in class A

After that remove the listener by using remove("eventID", "listenerID") from class SecondClass

Answer 3

You cannot expect that you can simply call some function in another class because you imported that class. The React way of doing this would be to pass the function as a prop if these are parent-child components. If not, I would highly recommend extracting the common function out from both classes and call them separately.

From the comments, other users have also recommended using static function if you absolutely want to couple the function to Second class.

My main objective is when user press the button then it should call the method from another class and return Hello. Then later i want to set some properties which i not possible in static function. So thats why i dont want to use static function

From your sample code it looks like Second is a React component ? If this class was made to encapsulate certain behavior then I would recommend turning it into a plain javascript class and then instantiate/use wherever necessary.