[英]React Native w/ TypeScript this.setState is not a function
我目前正在使用帶有最新TypeScript的React Native 0.39.2,當我運行componentDidMount()方法和setState時,我在this周圍收到錯誤.setState不是一個函數。
我嘗試使用this.setState({isLoggedIn: true}).bind(this)
盡管由於我使用布爾值作為類型,所以在不給出類型錯誤的情況下我也不會允許我這樣做,即使設置為任何類型仍然會遇到相同的錯誤。
這是我的代碼
首先用我的狀態界面
import React, {
Component
} from 'react';
import { AppRegistry, View, StyleSheet, Text } from 'react-native';
import { Actions } from 'react-native-router-flux';
import Firestack from 'react-native-firestack';
const firestack = new Firestack();
interface Props {
}
interface State {
isLoggedIn?: boolean;
}
export default class MainList extends Component<Props, State> {
state = {
isLoggedIn: false,
};
constructor(props: any) {
super(props);
console.log("Is anyone logged in?: " + this.isLoggedIn);
}
isLoggedIn = this.state.isLoggedIn;
componentDidMount() {
if (!this.isLoggedIn) {
Actions.welcome();
}
firestack.auth.listenForAuth(function(evt: any) {
// evt is the authentication event
// it contains an `error` key for carrying the
// error message in case of an error
// and a `user` key upon successful authentication
if (!evt.authenticated) {
// There was an error or there is no user
//console.error(evt.error);
this.setState({isLoggedIn: false});
console.log("The state of isLoggedIn is: " + this.isLoggedIn);
} else {
// evt.user contains the user details
console.log('User details', evt.user);
this.setState({isLoggedIn: true});
console.log("The state of isLoggedIn is: " + this.isLoggedIn);
}
});
}
render() {
return (
<View style={styles.View}>
<Text style={styles.textLabel}>The main view</Text>
</View>
)
}
}
const styles = StyleSheet.create({
View: {
padding: 20
},
textLabel: {
fontSize: 20,
marginBottom: 10,
height: 20
},
textInput: {
height: 20,
fontSize: 15,
marginBottom: 20
}
});
AppRegistry.registerComponent('MainList', ()=> MainList);
我在這里想念什么嗎?
問題是因為在listenForAuth
的回調函數中, this
不再引用MainList
對象。
嘗試切換到箭頭函數表達式來解決this
綁定問題:
firestack.auth.listenForAuth((evt: any) => {
...
});
如果您想了解更多有關箭頭功能的信息,請閱讀這里 。
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