React Native之函數作為參數傳遞給另外一個函數去調用

1 用法

我們一般喜歡把js裡面的函數作為參數傳遞給另外一個函數,然後再調用這個函數,有點像C語言裡面的函數指針

2 代碼測試

寫了一個函數,2個參數分别是函數,然後更具資料決定調用哪個函數

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow
 */
 
import React, {Component} from 'react';
import {Platform, StyleSheet, Text, View, NativeModules} from 'react-native';
 
const instructions = Platform.select({
  ios: 'Press Cmd+R to reload,\n' + 'Cmd+D or shake for dev menu',
  android:
    'Double tap R on your keyboard to reload,\n' +
    'Shake or press menu button for dev menu',
});
export default class App extends Component<Props> {
   
    constructor(props){
        super(props);
        this.state={
            myName:'chenzixuan',
        }
    }
   componentDidMount() { 
    this.load((name) => {console.log(name);}, (name) => {console.log(name); console.log(name);});
   }
  render() {
    return (
      <View style={styles.container}>
        <Text onPress={()=> this._androidShowMsg()} style={styles.welcome}>Welcome to React Native!</Text>
        <Text style={styles.instructions}>To get started, edit App.js</Text>
        <Text style={styles.instructions}>{instructions}</Text>
        <Text style={styles.instructions}>{this.state.myName}</Text>
      </View>
    );
  }
 
  load = (resolve, callback) => {
       let name = this.state.myName;
       if (name === 'chenzi1xuan') {
           resolve(name);      
       } else {
               callback(name);     
       }
  };
}
 
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
  instructions: {
    textAlign: 'center',
    color: '#333333',
    marginBottom: 5,
  },
});      

3 結果列印如下

很明顯,我們會調第二個參數的函數,是以日志會列印兩次name,日志如下

ReactNativeJS  I  Running application "pro_react" with appParams: {"rootTag":1}. __DEV__ === false, development-level warning are OFF, performance optimizations are ON
                         I  chenzixuan
                         I  chenzixuan