小编s2t*_*2t2的帖子

如何handleButtonPress在此示例React组件中调用消息映射内部？

import React, { Component } from 'react';
import {View, Text, TouchableOpacity} from 'react-native';

export default class MyComponent extends Component {
  constructor(props){
    super(props)
    this.state = {messages:["THANKS", "MERCI", "GRAZIE"]}
    this.myFunc = this.myFunc.bind(this)
    this.handleButtonPress = this.handleButtonPress.bind(this)
  }

  render(){
    return (
      <View>
        <Text>{this.state.message}</Text>

        {
          this.state.messages.map(function(message, index){
            return (
              <TouchableOpacity key={index} onPress={function(){ this.handleButtonPress(message) }.bind(this) }>
                <Text>Press Me</Text>
              </TouchableOpacity>
            )
          })
        }

      </View>
    )
  }

  handleButtonPress(message){
    console.log("BUTTON WAS PRESSED WITH MESSAGE: " + message)
    this.myFunc(message)
  }

  myFunc(message){
    console.log("MY FUNCTION WAS CALLED")
    this.setState({message:message})
  } …

在Ruby中，是否可以从超类方法转换为子类方法而又不影响子类中的代码？我试图避免super在子类中调用。

class SuperClass
  def do_something
    puts "getting ready..."
    # how to then yield back to the subclass do_something method?
    puts "done."
  end
end

class SubClass < SuperClass
  def do_something
    # how to first execute the superclass do_something method?
    puts "doing something ..."
  end
end

所需的功能是专门调用SubClass.do_something并接收以下输出：

“准备...”

“做某事...”

“做完了。”

编辑：

也许真正的问题是：如何干涸下面的代码，删除对来电self.get_ready和self.finish_up所有子类，使用任何红宝石的元编程技术，保持这些类DRY：

class SuperClass
  def self.get_ready
    puts "getting ready ..."
  end

  def self.finish_up
    puts "done."
  end
end

class SubClassA < SuperClass
  def self.do_something
    self.get_ready …

在MySQL group_concat()子句中,我正在尝试对case语句的结果值进行排序.以下查询配置正确things.name排序,但未在同一上下文中排序"非美国"或"未知"值.

SELECT 
  things.id
  ,group_concat(DISTINCT 
    CASE
    WHEN things.name <> 'United States' THEN 'Non-US'
    WHEN things.name IS NULL THEN 'Unknown'
    ELSE things.name
    END
  ORDER BY name SEPARATOR ', ')
FROM things
GROUP BY things.id

我想做这样的事情,但它不起作用:

SELECT 
  things.id
  ,group_concat(DISTINCT 
    (CASE
    WHEN things.name <> 'United States' THEN 'Non-US'
    WHEN things.name IS NULL THEN 'Unknown'
    ELSE things.name
    END) AS new_name
  ORDER BY new_name SEPARATOR ', ')
FROM things
GROUP BY things.id

有没有办法按"new_name"排序而不使用子查询/嵌套查询？

我正在尝试使用结构化数据来指定多个组织（见下文）。但谷歌的结构化数据测试工具只能识别每种类型的第一项。

如何列出多个alumniOf项目？

<script type="application/ld+json">
  {
    "@context": "http://schema.org",
    "@type": "Organization",
    "name": "My Org",
    "founder": {
      "@type": "Person",
      "name":"Me",
      "alumniOf":{
        "@type": "Organization",
        "name": "My Org 1"
      },
      "alumniOf":{
        "@type": "Organization",
        "name": "My Org 2"
      }

  }
</script>