React组件中的未定义参数

Question

I have a navbar component with a simulated login that brings me the user email from a modal but when I send an attribute to my signinmenu component the emails shows as undefined.

I also send a signout function and this is working but thje string email appears as undefined

navbar component

render() {
    const { auth } = this.props;
    const authenticated = auth.authenticated;

    return (
      <Menu inverted fixed="top">
        <Container>
          <Menu.Item as={Link} to="/" header>
            <img src="/assets/images/logo.png" alt="logo" />
            Re-vents
          </Menu.Item>
          <Menu.Item as={NavLink} to="/events" name="Events" />
          <Menu.Item as={NavLink} to="/test" name="Test" />
          {authenticated &&
          <Menu.Item as={NavLink} to="/people" name="People" />}

          {authenticated &&
          <Menu.Item>
            <Button
              as={Link}
              to="/createEvent"
              floated="right"
              positive
              inverted
              content="Create Event"
            />
          </Menu.Item>}
          {authenticated ? (
            <SignedInMenu currentUser={auth.currentUser} signOut={this.handleSignOut} /> 
          ) : (
            <SignedOutMenu signIn={this.handleSignIn} register={this.handleRegister} />
          )}
        </Container>
      </Menu>
    );
  }
}

SignInMenu component

import React from 'react';
import { Menu, Image, Dropdown } from 'semantic-ui-react';
import { Link } from 'react-router-dom'

const SignedInMenu = ({signOut, currentuser}) => {
  console.log(currentuser)
  return (
    <Menu.Item position="right">
      <Image avatar spaced="right" src="/assets/images/user.png" />
      <Dropdown pointing="top left" text={currentuser}>
        <Dropdown.Menu>
          <Dropdown.Item text="Create Event" icon="plus" />
          <Dropdown.Item text="My Events" icon="calendar" />
          <Dropdown.Item text="My Network" icon="users" />
          <Dropdown.Item text="My Profile" icon="user" />
          <Dropdown.Item as={Link} to='/settings' text="Settings" icon="settings" />
          <Dropdown.Item onClick={signOut} text="Sign Out" icon="power" />
        </Dropdown.Menu>
      </Dropdown>
    </Menu.Item>
  );
};

export default SignedInMenu;


I know the string is on the props but when I tried to show in the text attribute or console.log appears as undefined

Answer 1

This is a case typo - you're passing the prop as currentUser in the parent component, and receiving it as currentuser in the child. You need

<SignedInMenu currentuser={auth.currentUser} signOut={this.handleSignOut} /> 

It's tricky to avoid these sorts of problems, but using React PropTypes can help in some circumstances, you could consider adding them to your project.

Answer 2

SignedInMenu is a functional component and all its props contains in first argument. so you need to use it like this:

SignedInMenu = (props) => {
  return <h1>Hello, {props.name}</h1>;
}