小编TOM*_*MOM的帖子

嗨,我是React的新手,所以请耐心等待.我想将地理位置存储为州.看起来很漂亮,因为任何位置变化都会触发渲染,这正是我想要的.在开发过程中,我有一个按钮,通过访问手动触发事件lastPosition.但是,当我这样做.国家是"未定义的".有什么线索的原因？

export default class FetchProject extends Component {
    constructor(props) {
        super(props);
        this.state = {
            initialPosition: 'unknown',
            lastPosition: 'unknown',
        };
    }

    //code that sets lastposition
    componentDidMount() {
        ....
    }

    _onPressGET (){
        console.log("PressGET -> " + this.state); //undefined
        var northing=this.state.initialPosition.coords.latitude; 
        //triggers error
    }

    render() {
       return (    
           <View style={styles.container}>
               <TouchableHighlight onPress = {this._onPressGET} style = {styles.button}>
                  <Text>Fetch mailbox</Text>
               </TouchableHighlight>
           </View>
       );
    }
}

我是一个渴望接触 Ruby on Rails (OSX 10.7) 的 n00b。但首先我需要安装它。现在我花了 9 个小时试图让它工作，但是当我尝试创建一个新项目时它总是失败：

$ rails new /Users/tom/Documents/14-Utveckling/WhichTerminal 
   exist  
identical  README.rdoc
identical  Rakefile
identical  config.ru
identical  .gitignore
 conflict  Gemfile
Overwrite /Users/tom/Documents/14-Utveckling/WhichTerminal/Gemfile? (enter "h" for help) [Ynaqdh] Y
   force  Gemfile
   exist  app
identical  app/assets/images/rails.png
identical  app/assets/javascripts/application.js
identical  app/assets/stylesheets/application.css
identical  app/controllers/application_controller.rb
identical  app/helpers/application_helper.rb
    exist  app/mailers
    exist  app/models
identical  app/views/layouts/application.html.erb
identical  app/mailers/.gitkeep
identical  app/models/.gitkeep
    exist  config
 identical  config/routes.rb
identical  config/application.rb
identical  config/environment.rb
   exist  config/environments
identical  config/environments/development.rb
identical  config/environments/production.rb
identical  config/environments/test.rb
    exist  config/initializers
identical  config/initializers/backtrace_silencers.rb
identical  config/initializers/inflections.rb
identical …