javascript - 我是否正确使用了 Promise？

Question

我现在正在做一个学校项目，我想使用 promise 来实现我的“匹配功能”，但显然我做错了。我有一个约会网站，用户可以在其中结识其他人并与他们“匹配”。这就是想法。我正在做一个建议，所以它会自动建议配置文件。到目前为止，我可以为“异性恋用户”推荐人们，但在这里我试图为“双性恋用户”推荐，但我无法让它发挥作用。

我有一个名为 getPotentialsLocation() 的函数，如果我给它我的“直接用户”表 (straightPotentials)，它会完美地工作，但它可以进入我的其他条件 (else if (biPotentials))

为什么？我周围的每个人都尝试过，但我们找不到任何答案。

因此，如果我尝试获取“直接用户”，它会返回包含位置和所有内容的行。如果我尝试“bi users”，它会阻塞，因为它无法进入其他条件事件，尽管我可以一直 console.log(biPotentials) 。

我希望我的代码有意义，如果没有请告诉我。因为我要在这里链接很多代码

router.post('/matchaSearch', function (req, res) {
 var username = session.uniqueID;
 var searcherInfos = {};
 var straightPotentials = [];
 var biPotentials = [];

 function suggestUsers(){
  return new Promise((resolve, reject) => {
   pool.getConnection((err, connection) => {
    var query = 'SELECT sex, orientation FROM usersinfo WHERE username = ?';
    connection.query(query, [username], (err, rows, fields) => {
      connection.release()
      return err ? reject(err) : resolve(rows)
    })
  })
 })
}

suggestUsers()
.then((rows) => {
  searcherInfos = rows;
  if (searcherInfos[0].sex === 'm' && searcherInfos[0].orientation === 's'){
    console.log("searcher is straight");
    lookForSF()
      .then((rows) => {
        if (rows) {
          for (var i = 0; i < rows.length; i++) {
            straightPotentials.push(rows[i].username)
          }
          if (straightPotentials){
            console.log("straightPotentials" + straightPotentials);
            getPotentialsLocation()
            .then((rows) => {
              console.log(rows);
            }).catch((err) => {
              throw err;
            })
          }
        }
      }).catch((err) => {
      throw err;
      });


  } else if ((searcherInfos[0].sex) && searcherInfos[0].orientation === 'b'){
    console.log("searcher is bi");
    lookForbothCauseImB()
      .then((rows) => {
        if (rows) {
          for (var i = 0; i < rows.length; i++) {
            biPotentials.push(rows[i].username)
          }
          if (biPotentials){
            console.log("biPotentials" + biPotentials);
            getPotentialsLocation()
            .then((rows) => {
              console.log(rows);
            }).catch((err) => {
              throw err;
            })
          }
        }
      }).catch((err) => {
        throw err;
      })
    }

//this is the .catch for my first function (suggestUsers())
}).catch((err) => {
  throw err;
})



function lookForSF(){
  return new Promise((resolve, reject) => {
    pool.getConnection((err, connection) => {
      var query = 'SELECT username FROM usersinfo WHERE sex = "f" AND orientation = "s" AND username != ?';
      connection.query(query, [username], (err, rows, fields) => {
        connection.release()
        return err ? reject(err) : resolve(rows)
      })
    })
  })
}


function lookForbothCauseImB(){
  return new Promise((resolve, reject) => {
    pool.getConnection((err, connection) => {
      var query = 'SELECT username FROM usersinfo WHERE sex = "f" OR sex = "m" AND orientation = "s" OR orientation = "b" AND username != ?';
      connection.query(query, [username], (err, rows, fields) => {
        connection.release()
        return err ? reject(err) : resolve(rows)
      })
    })
  })
}


function getPotentialsLocation(){
  if (straightPotentials) {
    var string = '('
    for (var i =0; i <straightPotentials.length - 1; i++){
      string += '\'' + straightPotentials[i] + '\', ';
    }
    string += '\'' + straightPotentials[straightPotentials.length - 1] + '\')';
    return new Promise((resolve, reject) =>{
      pool.getConnection((err, connection) => {
        var query = 'SELECT * FROM userlocation WHERE username IN ' + string;
        console.log("this is our query " + query);
        connection.query(query, (err, rows, fields) => {
          connection.release();
          return err ? reject(err) : resolve(rows)
        })
      })
    })
  } else if (biPotentials) {
    var string = '('
    for (var i =0; i <biPotentials.length - 1; i++){
      string += '\'' + biPotentials[i] + '\', ';
    }

    string += '\'' + biPotentials[biPotentials.length - 1] + '\')';
    console.log("this is string" + string);
    return new Promise((resolve, reject) =>{
      pool.getConnection((err, connection) => {
        var query = 'SELECT * FROM userlocation WHERE username IN ' + string;
        console.log("this is our query " + query);
        connection.query(query, (err, rows, fields) => {
          connection.release();
          return err ? reject(err) : resolve(rows)
        })
      })
    })
  }
 }
})

Answer 1

如你所想，事实并非如此。

这个错误是嵌套 promise 反模式(谷歌搜索)

您的代码非常庞大，需要进行大规模重构才能以正确的方式进行设置

你在这里

function query (pool, sql, values) {
  return new Promise((resolve, reject) => {
    pool.getConnection((err, connection) => {
      var query = sql
      connection.query(query, values, (err, rows) => {
        connection.release()
        err ? reject(err) : resolve(rows)
      })
    })
  })
}

function suggestUsers (pool, username) {
  return query(pool, 'SELECT sex, orientation FROM usersinfo WHERE username = ?', [username])
}

function lookForSF (pool, username) {
  return query(pool, 'SELECT username FROM usersinfo WHERE sex = "f" AND orientation = "s" AND username != ?', [username])
}

function lookForbothCauseImB (pool, username) {
  return query(pool, 'SELECT username FROM usersinfo WHERE sex = "f" OR sex = "m" AND orientation = "s" OR orientation = "b" AND username != ?', [username])
}

function getPotentialsLocation (pool, potentials) {
  var usernames = potentials.map((potential) => {
    return "'" + potential + "'"
  })
  return query(pool, 'SELECT * FROM userlocation WHERE username IN (' + usernames.join(',') + ')')
}

function matchaSearch (pool, username) {
  return suggestUsers(pool, username)
      .then((searcherInfos) => {
        if (searcherInfos[0].sex === 'm' && searcherInfos[0].orientation === 's') {
          return lookForSF(pool, username)
        } else if ((searcherInfos[0].sex) && searcherInfos[0].orientation === 'b') {
          return lookForbothCauseImB(pool, username)
        }
      })
      .then((rows) => {
        var potentials = rows.map((row) => {
          return row.username
        })
        console.log('potentials' + potentials)
        return getPotentialsLocation(pool, potentials)
      })
}

router.post('/matchaSearch', function (req, res) {
  matchaSearch(pool, session.uniqueID)
    .then((results) => {
      console.log('result', results)
      res.send(JSON.stringify(results))
    })
    .catch((err) => {
      console.error('error', err)
      res.status(500).send('something wrong')
    })
})