如何在 JavaScript 中通过 Azure 移动服务自定义 API 使用 Promises/Chaining

Question

我正在尝试弄清楚如何将 Promises 与 AMS Javascript API 一起使用。

这是我创建的两个将被“承诺”的函数

function checkUsername(username, table) {
    
    return table.where({username: username}).read({
        success: function (results) {
            
            if (results.length === 0) {
                return true;   
            } else {
                return false;
            }
            
        },
        error: function(error) {
            return false;
        }
    });
    
}

function checkEmail(email, table) {
    
    return table.where({email: email}).read({
        success: function (results) {
            
            if (results.length === 0) {
                return true;   
            } else {
                return false;
            }
            
        },
        error: function(error) {
            return false;
        }
    });
    
}

checkUsername(body.username, accountsTable).then(function (results) {

  if (results) {
  
    return checkEmail(body.email, accountsTable);
  
  } else {
  
    response.send(400, {message: 'This username is already in use.'});
    
  }
  
}).then(function(results) {

  if (results) {
  
    response.send(200, {message: 'Can proceed with sign up.'});
    
  } else {
  
    response.send(400, {message: 'This email address is already in use.'});
    
  }
  
});

我正在尝试像在 Parse 中一样使用 Promise，但它显然不起作用。控制台日志不断吐出内部服务器错误，并且 .then() 不是对象的函数。我假设我缺少一个要求或其他东西才能拥有 Promises 功能？

Error in script '/api/register.js'. TypeError: Cannot call method 'done' of undefined
at exports.post (D:\home\site\wwwroot\App_Data\config\scripts\api\register.js:30:59)
[external code]

Answer 1

我已经意识到我做错了什么。

我现在决定使用 Q 节点模块来实现我的承诺。

var q = require('q');

exports.post = function(request, response) {
    // Use "request.service" to access features of your mobile service, e.g.:
    //   var push = request.service.push;
    
    var tables = request.service.tables;
    
    var accountsTable = tables.getTable('Accounts');
    
    var params = request.body;
    
    checkUsername(params.username, accountsTable).then(function (result) {
       
        if (result.length === 0) {
         
            return checkEmail(params.email, accountsTable);
            
        } else {
         
            response.send(400, {message: 'This username is in use.'});
            
        }
        
    }).then(function (results) {
      
        if (results.length === 0) {
         
            return;
            
        } else {
         
            response.send(400, {message: 'This email address is already registered.'});
            
        }
        
    }).then(function () {
      
        response.send(200, {message: 'Username and email are unique. You can register!'});
        
    });
    
};

function checkUsername(username, table) {
    
    var deferred = q.defer();
    
    table.where({username: username}).read({
        success: function (result) {
            deferred.resolve(result);
        },
        error: function (error) {
            deferred.reject(error);   
        }
    });
    
    return deferred.promise;
    
}

function checkEmail(email, table) {
 
    var deferred = q.defer();
    
    table.where({email: email}).read({
        success: function (result) {
            deferred.resolve(result);
        },
        error: function (error) {
            deferred.reject(error);   
        }
    });
    
    return deferred.promise;
    
}