Javascript 链接多个承诺（处理回调）
当涉及到链接多个承诺时，我在承诺方面遇到了一些困难。混淆之处在于如何正确利用承诺及其与回调的区别。我注意到，无论承诺是否得到解决，回调有时会触发，这使得下面的实现不可靠。（Javascript 链接多个承诺（处理回调）,javascript,angularjs,promise,angular-promise,Javascript,Angularjs,Promise,Angular Promise,当涉及到链接多个承诺时，我在承诺方面遇到了一些困难。混淆之处在于如何正确利用承诺及其与回调的区别。我注意到，无论承诺是否得到解决，回调有时会触发，这使得下面的实现不可靠。（除非我的语法和逻辑错误）我阅读了官方文档并提出了这个方法，但我不确定它是否得到了很好的实现。注册流程如下： function do_all() { var task_1 = function() {
除非我的语法和逻辑错误）
我阅读了官方文档并提出了这个方法，但我不确定它是否得到了很好的实现。
注册流程如下：
function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
- 用户选择别名->详细信息别名+用户ID（设备的通用唯一标识符）发送到服务器端
- 如果别名可用，则生成ApiKey（令牌），用户注册并发送回客户端（存储在DB中）
(function(angular) {
myApp.factory("deviceDB.Service", ['$resource', '$http', '$q',
function ($resource, $http , $q ) {
return {
//Second Promsie : After API token is generated server-side, store res in db
RegDevice: function (alias, apiKey, userID) {
var deferred = $q.defer();
var configuration ;
var db = window.sqlitePlugin.openDatabase({name: "config.db"});
setTimeout(function () {
db.transaction(function (tx) {
tx.executeSql('CREATE TABLE IF NOT EXISTS user_details (userID UNIQUE , alias TEXT, apiKey TEXT)');
tx.executeSql("INSERT INTO user_details (userID, alias, apiKey) VALUES (?,?,?)", [userID, alias, apiKey], function (tx, res) {
deferred.resolve(configuration = true);
}, function (e) {
// console.log("ERROR: " + e.message);
deferred.reject(configuration = false);
});
});
}, 1000);
return deferred.promise;
},
//First Promsie: Register user server side & generate APi token
RegUser: function (alias, userID) {
var deferred = $q.defer();
var pro;
pro = $resource('api/query/register', {'alias': alias, 'userID': userID},
{ query: {
isArray: false,
method: 'GET' } });
setTimeout(function () {
pro.query(function (res) {
if (res.error) {
deferred.reject( { error : res.error, exists: res.exists, msg: res.message } );
}
else {
deferred.resolve( {error : res.error , alias: res.alias , apiKey: res.apiKey, msg: res.message } );
}
}, function (e) {
deferred.reject( { errorStatus: e.status } );
});
}, 1000);
return deferred.promise;
}
};
}]);
}(window.angular));
function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
现在，在我的控制器中，我想链接上面的两个承诺。我引用文档中的以下内容：
function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
then（successCallback、errorCallback、notifyCallback）function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
我尝试的：
Controller.js
myApp.controller('RegisterController', ['$scope', '$http', 'deviceDB.Service',
function ($scope , $http , deviceDB.Service) {
var Promise1 = deviceDB.RegUser($scope.alias, $scope.Device);
// First promise - Validate with server
Promise1.then(function(data)
{
console.log(' Registration Server-Side successfully');
$scope.apiKey = data.apiKey;
term.echo(data.apiKey);
}, function(e)
{
console.log('Registration Failed');
term.echo(e.msg);
})
//Call Promise 2 & Store details Client-Side using .then()
.then(deviceDB.RegDevice($scope.alias, $scope.apiKey, $scope.Device),
function(d){
console.log('Items Stored in DB successfully');
}, function()
{
console.log('Items Stored in DB Failed');
});
}]);
function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
感谢您抽出时间您的第二个then电话似乎不正确
//Call Promise 2 & Store details Client-Side using .then()
function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
thenthen（successCallback、errorCallback、notifyCallback）deviceDB.RegDevice（$scope.alias、$scope.apiKey、$scope.Device）thenfunction do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
Promise1.then(function(data)
{
console.log(' Registration Server-Side successfully');
$scope.apiKey = data.apiKey;
term.echo(data.apiKey);
return deviceDB.RegDevice($scope.alias, $scope.apiKey, $scope.Device)
}, function(e)
{
console.log('Registration Failed');
term.echo(e.msg);
return e;
}).then(function(d) {/*all good*/}, function(e) {/* all bad */}
function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
以下是一种使用async/await可能会有所帮助的方法：
function do_all() {
var task_1 = function() {
return $http.get("some url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_2 = function(some_data) {
vm.bla = some_data;
return $http.get("other url")
.then(on_xhr_completed_fn, on_xhr_failed_fn);
}
var task_3 = function(other_data) {
vm.bli = other_data;
}
var tasks = [task_1, task_2, task_3];
return $q.serial(tasks)
.then(function() {
console.log("Finished tasks 1, 2 and 3!!!");
});
}
async function run_promise_A(args) {
return new Promise((resolve, reject) => {
return resolve(resolve_value)
});
}
async function run_promise_B(args) {
return new Promise((resolve, reject) => {
return resolve(resolve_value)
});
}
async function run_promise_C(args) {
return new Promise((resolve, reject) => {
return resolve(resolve_value)
});
}
async function run_several_async_functions(userid) {
let a = run_promise_A(userid);
let b = run_promise_B(a);
let c = run_promise_C(b);
return c;
}
return Promise.resolve()
.then(() => {
let c = (async () => {
let c = await run_several_async_functions(userid)
return c;
})();
return c;
})
.then((c) => {
return c;
})
.catch((err) => {
console.log(err);
});
因此，如果我理解正确，这里Promise1接受3个参数，返回的promise RegDevice在成功回调中（放置在第一个Arumgin中）。它工作正常，事件同步触发，首先Promise1，然后2。第二个then（）[函数（d）success/函数（e）error是promise2的回调吗？因此，如果我有3个承诺，我会从函数（d）return中调用第三个，以此类推