反应this.setState不是一个函数 [英] React this.setState is not a function

问题描述

我是React的新手，我正在尝试编写一个使用API​​的应用程序。我一直收到这个错误：

I'm new in React and I'm trying to write an app working with an API. I keep getting this error:

TypeError：this.setState不是函数

TypeError: this.setState is not a function

当我尝试处理API响应时。我怀疑这个绑定有问题，但我无法弄清楚如何修复它。这是我的组件的代码：

when I try to handle the API response. I suspect it's something wrong with this binding but I can't figure out how to fix it. Here's the code of my component:

var AppMain = React.createClass({
    getInitialState: function() {
        return{
            FirstName: " "
        };
    },
    componentDidMount:function(){
        VK.init(function(){
            console.info("API initialisation successful");
            VK.api('users.get',{fields: 'photo_50'},function(data){
                if(data.response){
                    this.setState({ //the error happens here
                        FirstName: data.response[0].first_name
                    });
                    console.info(this.state.FirstName);
                }

            });
        }, function(){
        console.info("API initialisation failed");

        }, '5.34');
    },
    render:function(){
        return (
            <div className="appMain">
            <Header  />
            </div>
        );
    }
});

推荐答案

回调是在不同的上下文中进行的。您需要绑定到此才能在回调中访问：

The callback is made in a different context. You need to bind to this in order to have access inside the callback:

VK.api('users.get',{fields: 'photo_50'},function(data){
    if(data.response){
        this.setState({ //the error happens here
            FirstName: data.response[0].first_name
        });
        console.info(this.state.FirstName);
    }

}.bind(this));

编辑：
看起来你必须绑定 init 和 api 来电：

VK.init(function(){
        console.info("API initialisation successful");
        VK.api('users.get',{fields: 'photo_50'},function(data){
            if(data.response){
                this.setState({ //the error happens here
                    FirstName: data.response[0].first_name
                });
                console.info(this.state.FirstName);
            }

        }.bind(this));
    }.bind(this), function(){
    console.info("API initialisation failed");

    }, '5.34');

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