How to use if else condition inside nested map function in react-native?

问题

I am making a react-native app that has a custom view like a grid view. All the cells of the view have same size except one. I want to give condition for the cell to have double the size from others.
I am making the view through an array using map function. Map function is not taking if statement. How should I use it?

// Buttons Array
buttons = [['1', '2', '3'],
           ['a', 'b', 'c'],
           ['q', 'w', 'e'],
           ['+', '-', '*'],
          ]
// '-' has double size...
import React, { Component } from 'react';
import {
    View,
    Text,
    TouchableNativeFeedback
} from 'react-native';

//Styles
import styles from './styles';

export default class NumberButtons extends Component {



    //This will call the bound function from its parent component 
    //to handle button press action/event 
    _handleOnPress = (value) => {
        requestAnimationFrame(() => {
            this.props.onBtnPress(value);
        });
    }

    render() {
        return (
            <View style={styles.container}>
                {
                    this.props.buttons.map((row, index) => (
                        <View key={index} style={styles.contRow}>
                            { 
                                row.map((col,index) => (
            //**** Here I want to use if else for row and column ***//
                                    <TouchableNativeFeedback
                                        key={index}
                                        onPress={() => this._handleOnPress(col)}
                                        background={TouchableNativeFeedback.SelectableBackground()}>
                                        <View style={styles.buttonContainer}>
                                            <Text style={styles.text}>{col}</Text>
                                        </View>
                                    </TouchableNativeFeedback>
                                ))
                            }
                        </View>
                    ))
                }
            </View>
        );
    }
}

回答1:

You can render conditional views like this

            <View style={styles.container}>
                 {this.state.buttons.map((row, index) => {
                    const myRow = row
                    console.log("myRow",myRow)
                    return (
                     <View key={index} style={styles.contRow}>
                         {
                             row.map((col,index) => {
                                  if(col != 3 && myRow != null  ){
                                    return (
                                      <TouchableNativeFeedback
                                          key={index}
                                          onPress={() => this._handleOnPress(col)}
                                          background={TouchableNativeFeedback.SelectableBackground()}>
                                          <View style={styles.buttonContainer}>
                                              <Text style={styles.text}>{col}</Text>
                                          </View>
                                      </TouchableNativeFeedback>
                                    )
                                  }
                                  else  {
                                    return (
                                      <TouchableNativeFeedback
                                          key={index}
                                          onPress={() => this._handleOnPress(col)}
                                          background={TouchableNativeFeedback.SelectableBackground()}>
                                          <View style={styles.buttonContainer}>
                                              <Text style={{backgroundColor:'#78909C'}}>{col}</Text>
                                          </View>
                                      </TouchableNativeFeedback>
                                    )
                                  }
                             })
                         }
                     </View>
                 )})
             }
         </View>

回答2:

Here is the sample code how you can insert if and else in the nested map function.

this.props.availableEvents.map((item, i) => {
      
      if (i < this.state.imageIndex) {
        return null
      } else if (i === this.state.imageIndex) {
        return (
          <Animated.View
            {...this.imagePanResponder.panHandlers}
            key={i}
            style={[this.rotateAndTranslate, styles.cardContainer]}
          >
           
              <View style={{ width: '100%', height: '100%' }}>
                
              </View>
           
          </Animated.View>
        )
      } else {
        return (
          <Animated.View
            key={i}
            style={styles.cardContainer}>
            <View style={{ width: '100%', height: '100%' }}>
              
            </View>
          </Animated.View>
        )
      }
    }).reverse();
  };

来源：https://stackoverflow.com/questions/54605677/how-to-use-if-else-condition-inside-nested-map-function-in-react-native