Ionic Contact插件

Question

Iam使用Ionic 4通过离子接触插件访问手机号码， 但是我在兑现承诺方面遇到了错误

        import { Component, OnInit} from '@angular/core';
    import {Contacts,Contact,IContactFindOptions,ContactFieldType,} from '@ionic-native/contacts/ngx';

    @Component({
      selector: 'app-tab1',
      templateUrl: 'tab1.page.html',
      styleUrls: ['tab1.page.scss']
    })
    export class Tab1Page implements OnInit {

      contact:Contact
      field:ContactFieldType[] = ["displayName", "phoneNumbers"];
      constructor(private contacts:Contacts
                  ){
      }
      test:any = [];
      ngOnInit(){

      }
      getContacts(){
         let options:IContactFindOptions = {
           filter:'r',

         }
        this.contacts.find(this.field,options)
        .then((contacts) => {
          console.log(contacts);
          for(let i=0;i<contacts.length;i++){
            let contact = {
              name:'',
              phone:''
            }
            contact.name = contacts[i].displayName;
            contact.phone = contacts[i].phoneNumbers[0].value;
            this.test.push(contact);
          }

        });

      }
    }

错误：

Tab1Page.html:13 ERROR TypeError: Cannot read property 'then' of undefined
    at Tab1Page.push../src/app/tab1/tab1.page.ts.Tab1Page.getContacts (tab1.page.ts:25)
    at Object.eval [as handleEvent] (Tab1Page.html:13)
    at handleEvent (core.js:23107)
    at callWithDebugContext (core.js:24177)
    at Object.debugHandleEvent [as handleEvent] (core.js:23904)
    at dispatchEvent (core.js:20556)
    at core.js:21003
    at HTMLElement.<anonymous> (platform-browser.js:993)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:423)
    at Object.onInvokeTask (core.js:17290)