承诺从我的服务中返回未定义

Posted 2023-03-16

【中文标题】承诺从我的服务中返回未定义

【英文标题】：Promise return undefined from my service

【发布时间】：2016-08-17 23:03:13

【问题描述】：

我使用websql 从 web sql 获取我的数据

我创建了我的控制器、我的模型和我的服务：

服务

app.project.service('ProjectService', ['$webSql', 'config', function ($webSql, config) 

    var db = $webSql.openDatabase('MyApp', '1.0', 'MyApp', 2 * 1024 * 1024);

    this.getAll = function (params) 
        var projects = [];
        db.selectAll("projects").then(function(results) 
            for(var i=0; i < results.rows.length; i++)
                projects.push(results.rows.item(i));
            
            return projects;
        )
    ;

    this.create = function (project) 
        return db.insert('projects', project).then(function(results) 
            console.log(results.insertId);
        );
    ;

    this.createTable = function () 
        return db.createTable('projects', 
            "id":
                "type": "INTEGER",
                "null": "NOT NULL", // default is "NULL" (if not defined)
                "primary": true, // primary
                "auto_increment": true // auto increment
            ,
            "created":
                "type": "TIMESTAMP",
                "null": "NOT NULL",
                "default": "CURRENT_TIMESTAMP" // default value
            ,
            "name":
                "type": "TEXT",
                "null": "NOT NULL"
            ,
            "path": 
                "type": "TEXT",
                "null": "NOT NULL"
            ,
            "file": 
                "type": "TEXT",
                "null": "NOT NULL"
            
        );
    ;

]);

型号

app.project.factory('Project', function (ProjectService) 

    var Project = function (properties) 
        // Model
        this.file    = null;
        this.name      = null;
        this.path  = null;
        this.is_active = null;

        angular.extend(this, properties);
    ;

    Project.prototype.setModel = function (obj) 
        angular.extend(this, obj);
    ;

    // With service
    // ------------------------------------------------------------------------------------------------------
    // ------------------------------------------------------------------------------------------------------

    Project.prototype.getAll = function () 
        return ProjectService.getAll();
    ;

    Project.prototype.create = function (project) 
        return ProjectService.create(project);
    ;

    Project.prototype.createTable = function () 
        return ProjectService.createTable();
    ;

    return Project;

);

控制器

app.home.controller('HomeController', ['$scope', '$http', '$webSql', 'Project', function ($scope, $http, $webSql, Project) 

    var project = new Project();

    $scope.refresh = function()

        new_project = "name": 'Project1 WEB PREPROD', "path": 'project1.preprod.site.com', 'file': '/release.txt';

        // project.createTable();

        project.create(new_project);

        $scope.projects = project.getAll();

        console.log(project.getAll());
    ;

    $scope.refresh();
]);

我可以 createTable 并创建一个新对象（项目），但是当我执行$scope.projects = project.getAll(); 我的控制台日志返回undefined

我在我的服务中尝试过这个

this.getAll = function (params) 
            var projects = [];
            db.selectAll("projects").then(function(results) 
                for(var i=0; i < results.rows.length; i++)
                    projects.push(results.rows.item(i));
                
            ).then(function() 
                return projects;
            )
        ;

但我有同样的问题

【参考方案1】：

您错过了从服务getAll 方法返回承诺。基本上db.selectAll 函数会返回一个承诺，而您不会返回。

this.getAll = function (params) 
    //return promise from here.
    return db.selectAll("projects").then(function(results) 
        for(var i=0; i < results.rows.length; i++)
            projects.push(results.rows.item(i));
        
        return projects;
    )
;

并替换它：

$scope.projects = project.getAll();

通过

project.getAll().then(function(results) 
    $scope.projects = results;
);

【讨论】：

但我添加了这个 .then(function() return projects; );在我的函数 db.selectAll 之后？我该怎么做？

@JérémieChazelle 内部返回只是链接promise，第一个地方你还没有返回承诺对象..