TypeError：无法在React Component中读取未定义的属性'fetchAll'

我正在使用Mobx-React创建一个小应用程序 . 我创建了一个成员库并拥有一个asyn fetchAll方法 . （见下文）

import {observable, action, computed} from 'mobx';

class MemberStore {
@observable members = [];
@observable isLoading = false;

@action async fetchAll() {
    this.isLoading = false;
    const response = await fetch('http://localhost:3000/v1/members');
    const status = await response.status;
    if (status === 200) {
        this.members = response.json();
    } 
}

前端是一个Contact页面，其中包含以下代码 .

import React, { Component } from 'react';
import Navbar from '../components/Navbar';
import Footer from '../components/Footer';
import Jumbotron from '../components/Jumbotron';
import {inject, observer} from 'mobx-react';

@inject('MemberStore')
@observer

class Contact extends Component {
  componentWillMount(){
    this.props.members.fetchAll();
}
handleSubmit = (e) => {
    e.preventDefault();

    const name = this.member.value;
    const email = this.email.value;
    // const email = this.email.value;
    this.props.MemberStore.addMember({name, email});
    this.member.value = '';
    this.email.value = '';
}
render() {
    const {MemberStore} = this.props;

    return (
        <div>
            <Navbar />
            <Jumbotron title="Contact Page" subtitle="You want to get in touch"/>
            <div className="container">
               <h2>You have {MemberStore.memberCount} members.</h2>

               <form onSubmit={e => this.handleSubmit(e)}>
                   <input type="text" placeholder="Enter Your Name" ref={input => this.member = input }/>
                   <div>
                   <input type="text" placeholder= "Enter Your Email" ref={input => this.email = input }/>
                   </div>
                   <button>Submit</button>
               </form>
               <ul>
                {MemberStore.members.map(({name, email}, index) => (
                    <li key={index}>
                    <div>
                        name: {name}
                    </div>
                    <div>
                        email: {email}
                    </div>
                    </li>
                ))}
                </ul>
            </div>
            <Footer />
        </div>
    )
  }
}

export default Contact;

我不确定它是否应该 this.props.MemberStore.fetchAll() 但是给了我一个不同的 TypeError: MemberStore.members.map is not a function 错误 . 所以想知道我做错了什么，因为我以为我正在访问MemberStore组件中的fetchAll（）函数 .