TypeError：无法读取未定义的属性“ setState”

还绑定回调函数，以便

this

getPosts = () =>  {    $.ajax({        type: 'get',        url: urlname,        success: (data) => { this.setState( { posts: data } )        }    });}

或者你可以像这样使用bind

getPosts = () =>  {    $.ajax({        type: 'get',        url: urlname,        success: function(data) { this.setState({ posts: data })        }.bind(this)    });}