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 is not a function
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>
);
}
});
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));
EDIT:
Looks like you have to bind both the init and api calls:
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');
You can avoid the need for .bind(this) with an ES6 arrow function.
VK.api('users.get',{fields: 'photo_50'},(data) => {
if(data.response){
this.setState({ //the error happens here
FirstName: data.response[0].first_name
});
console.info(this.state.FirstName);
}
});
React recommends bind this in all methods that needs to use this of class instead this of self function.
constructor(props) {
super(props)
this.onClick = this.onClick.bind(this)
}
onClick () {
this.setState({...})
}
Or you may to use arrow function instead.