我刚刚开始使用ES6和React，我想在我的组件类中创建一个验证方法，以便在继续之前进行验证。
## if your data is in a data frame you can do it like this
your_data = zoo::na.locf(your_data, fromLast = TRUE)
## if your data is a list, do this
your_data = lapply(your_data, zoo::na.locf, fromLast = TRUE)
在反应组件中绑定实例方法与事件处理程序有什么不同吗？我有一个setUser方法，我传递给正确调用的子组件。但是当我尝试从loginUser eventHandler中调用class LoginPage extends React.Component {
constructor(props) {
super(props);
this.setUser = this.setUser.bind(this);
this.isFormValid = this.isFormValid.bind(this);
this.state = {
user: {
username: '',
password: ''
}
};
}
isFormValid() {
console.log("is valid");
let isValid = true;
let errors = {};
if (this.state.user.username.length <= 0) {
errors.username = "Username cannot be blank";
isValid = false;
}
if (this.state.user.password.length <= 0) {
errors.password = "Password cannot be blank";
isValid = false;
}
this.setState({ errors: errors });
return isValid;
}
setUser(event) {
let username = event.target.username;
let password = event.target.password;
this.setState({
user: {
username: username,
password: password
},
errors: {}
});
}
loginUser(event) {
event.preventDefault();
if (!this.isFormValid()) {
return;
}
}
render() {
return (
<LoginForm
user={this.state.user}
onChange={this.setUser}
onLogin={this.loginUser} />
);
}
时，我得到了
isFormValid答案 0 :(得分：2)
消息Cannot read property 'isFormValid' of null表示正在从null对象访问isFormValid。
含义，this方法中的loginUser为空。
因此绑定在构造函数中调用isFormValid的方法，即loginUser。
constructor(props) {
super(props);
/// other methods
this.loginUser = this.loginUser.bind(this);
}