[英]How to use promises correctly with callback function
我有此服務,它使用回調異步返回學生列表:
studentModule.factory('StudentService', function (DB_URL) {
return {
getAllStudents: function (callback) {
var Datastore = require('nedb'),
path = require('path');
db = {};
db.students = new Datastore({
filename: DB_URL + '/students.db',
autoload: true
});
db.students.find({}, function (err, stds) {
callback(stds);
});
}; //end return
我在控制器中使用它的舊方法:
StudentService.getAllStudents(function(sts) {
$scope.students = sts;
$scope.$apply();//notify angular about the change
});
這對我有用,但是現在我想使用一些最佳實踐。 我需要在到達控制器之前解決路由中的結果,這是我所做的:
.state('payment', {
url: '/payment',
templateUrl: 'frontend/components/payment/views/payment.html',
controller: 'PaymentController',
resolve: {
students: function (StudentService, $q) {
var defer = $q.defer();
defer.promise.then(function () {
StudentService.getAllStudents(function (sts) {
alert(JSON.stringify(sts));
return sts;
});
})
defer.resolve();
}
}
})
警報正在成功從路由返回數據,但未從控制器返回數據-我在控制器中得到未定義 :
paymentModule.controller('PaymentController', function($scope,students) {
alert(JSON.stringify(students));
任何幫助將不勝感激!
您應該始終返回一個承諾以解析功能,當創建自己的承諾時,應使用需要傳遞的數據來解決它。
.state('payment', {
url: '/payment',
templateUrl: 'frontend/components/payment/views/payment.html',
controller: 'PaymentController',
resolve: {
students: function (StudentService, $q) {
var defer = $q.defer();
//defer.promise.then(function () {
StudentService.getAllStudents(function (sts) {
//alert(JSON.stringify(sts));
//return sts;
defer.resolve(sts);
});
//})
//defer.resolve();
return defer.promise
}
}
})
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