javascript - 连接两个 promise

Question

我有两个 promise

    const promise_1 = this.connection.insertPatientToDataBase(Store.getPotentialPatientID())
      .then(ting => {
        console.log(ting);
        Dispatcher.dispatch({
        actionType: Constants.CHANGE_POTENTIAL_PATIENT_PASSWORD,
        payload: ting.data.password
      })})
      .catch(error => {console.log(error)});

    const promise_2 = this.connection.getAllPatientData()
      .then( function(response) {
        console.log("Dispatrinc a new server call")
        console.log(response.data)
       Dispatcher.dispatch({
        actionType: Constants.CHANGE_ALL_PATIENTS,
        payload: response.data
      })})
      .catch(error => console.log(error))


      console.log("Done");
  }

第一个将向服务器发布一些数据，第二个查询数据以重新下载新名单。第二个依赖于第一个。问题是第一个 promise 之后就兑现了。第二个 promise 首先兑现。我怎样才能将这两个 promise 链接在一起那么 Promise 2 会等待 Promise 1 吗？

Answer 1

如果两个函数不相关，但promise_1必须首先解析以便患者存在，您可以将promise创建包装在一个函数中，并且仅在promise_1解析时调用promise_2创建:

const promise_1 = () => this.connection.insertPatientToDataBase(Store.getPotentialPatientID())
  .then(ting => {
    console.log(ting);
    Dispatcher.dispatch({
    actionType: Constants.CHANGE_POTENTIAL_PATIENT_PASSWORD,
    payload: ting.data.password
  })})
  .catch(error => {console.log(error)});

const promise_2 = () => this.connection.getAllPatientData()
  .then( function(response) {
    console.log("Dispatrinc a new server call")
    console.log(response.data)
   Dispatcher.dispatch({
    actionType: Constants.CHANGE_ALL_PATIENTS,
    payload: response.data
  })})
  .catch(error => console.log(error));

  promise_1().then( response => promise_2());

如果promise_2依赖于promise_1的结果来运行，例如，如果promise_1将返回患者id，并且您需要该id来运行promise_2，并且只有promise_2的结果必须在两者解析后可用，那么您可以修改上面一点点来传递参数:

const promise_1 = () => this.connection.insertPatientToDataBase(Store.getPotentialPatientID())
      .then(ting => {
        console.log(ting);
        Dispatcher.dispatch({
        actionType: Constants.CHANGE_POTENTIAL_PATIENT_PASSWORD,
        payload: ting.data.password
      })})
      .catch(error => {console.log(error)});

const promise_2 = patient_id => this.connection.getAllPatientData( patient_id )
      .then( function(response) {
        console.log("Dispatrinc a new server call")
        console.log(response.data)
       Dispatcher.dispatch({
        actionType: Constants.CHANGE_ALL_PATIENTS,
        payload: response.data
      })})
      .catch(error => console.log(error));

promise_1()
  .then( patient_id => promise_2( patient_id ))
  .then( patient_data => {
    // handle patient data.
  });

您还可以将所有内容重组为更多的原子函数，因此每个 promise 都有一个特定的目标，因此您可以将它们全部链接在一起。如果您以不同的方式嵌套结构，您甚至可以保存所有响应并在最后返回所有 fo。

const create_patient_id = () => this.connection.insertPatientToDataBase(Store.getPotentialPatientID());

const create_patient = patient_id => Dispatcher.dispatch({
    actionType: Constants.CHANGE_POTENTIAL_PATIENT_PASSWORD,
    payload: patient_id.data.password
});

const get_patients = () => this.connection.getAllPatientData();

const update_patients = patients => Dispatcher.dispatch({
    actionType: Constants.CHANGE_ALL_PATIENTS,
    payload: patients.data
})

const workflow = () => create_patient_id()
  .then( create_patient );
  .then( get_patients )
  .then( update_patients );

 workflow();