相当于 angular 中的 $q.when 2

Question

我习惯用$q和angular 1.我正在迁移到angular 2.

是否有提供 .when() 方法的等效方法？

例如我需要迁移这个：

.service('updateProDB', [
            '$rootScope',
            'connectionStatus',
            '$q',
            'storageService',
            'sendToServer',
            '$ionicPopup',
            function ($rootScope, connectionStatus, $q, storageService, sendToServer, $ionicPopup) {
                'use strict';

                var dbReadyDeferred = $q.defer(),
                prodata = [],
                prodataFieldNames = [];

            this.get = function () {
                var debugOptionUseLocalDB = 0,
                    prodata = [],
                    serverAttempts = 0;

                if (debugOptionUseLocalDB) {
                    return fallbackToLocalDBfileOrLocalStorageDB();
                }
                if (connectionStatus.f() === 'online') {
                    console.log("Fetching DB from the server:");
                    return getDBfileXHR(dbUrl(), serverAttempts)
                            .then(function () { // success
                                console.log('-normal XHR request succeeded.');
                                return dbReadyDeferred.promise;
                            })
                            .catch(function (){

Answer 1

你可以做同样的事情，用：

Promise.resolve(promise).then

这基本上没有区分承诺和价值。

是的，您可以用相同的方式实例化 q，但使用 new Promise() 而不是 $q()

let promise = new Promise((resolve, reject) => {
    if (/* some async task */) {
       resolve('Success!');
    } else {
        reject('Oops... something went wrong');
    }
});

和

let promise = $q((resolve, reject) => {
    if (/* some async task */) {
       resolve('Success!');
    } else {
       reject('Oops... something went wrong');
    }
});

它们应该是等价的

相当于 angular 中的 $q.when 2

equivalent of $q.when in angular 2

observable

deferred

ionic2

angular