我的目标是包装 MySQL 查询，将参数传递给一个函数，然后另一个函数执行 MySQL 作业，返回结果。
到目前为止，这是我的代码:
//mysql lib
var mysql = require('mysql');
//database credentials
exports.pool = mysql.createPool({
connectionLimit: 50,
host: 'localhost',
user: 'root',
password: 'password',
database: '_app',
debug: false
});
//my wrapper =(
var returnResultset = exports.returnResultset = function (qry) {
return new Promise(function (resolve, reject) {
try {
mysql_.pool.getConnection(function (err, connection) {
if (err) {
console.log("Error on function returnResultset - MYSQL ERROR: " + err);
return reject(err);
}
connection.query(qry, [], function (error, results, fields) {
connection.release();
if (error) {
console.log("Error on function returnResultset - MYSQL ERROR: " + error);
return reject(error);
}
return resolve(results);
});
});
}
catch (e) {
console.log('error:' + e);
}
});
};
//wrapper function for testing purposes
var selectOneField = exports.selectOneField = function (tbl, field, pk, pkval) {
var qry_ = "SELECT " + field + " FROM " + tbl + " WHERE " + pk + " = '" + pkval + "'";
returnResultset(qry_).then(function (results) {
return results;
}, function (error) {
console.log("Error: " + error);
})
};
//...and on another page I want to be able to receive the results from the function above:
var isExpired = exports.isExpired = function (cod) {
var rtf = db_.selectOneField('view_expiredusers', 'cod', 'cod', cod);
console.log(rtf);
return rtf;
};
上面的代码返回undefined。我无法使此功能正常工作。
我试过 console.log(results)。查询就像一个魅力。我唯一无法开始工作的是从外部函数中获取结果。
有什么想法吗？提前致谢!
最佳答案
您应该返回 promise 并将其链接到 isExpired 函数中。
//wrapper function for testing purposes
var selectOneField = exports.selectOneField = function (tbl, field, pk, pkval) {
var qry_ = "SELECT " + field + " FROM " + tbl + " WHERE " + pk + " = '" + pkval + "'";
return returnResultset(qry_);
};
//...and on another page I want to be able to receive the results from the function above:
var isExpired = exports.isExpired = function (cod) {
return db_.selectOneField('view_expiredusers', 'cod', 'cod', cod)
};
当您在其他文件中调用 isExpired 时，您应该使用 promise 的 then 方法并返回结果。做如下
var cod_customer = 1;
var isexpired;
isExpired(cod_customer).then(function (results) {
isexpired = results;
console.log(isexpired);
}, function (error) {
console.log("Error: " + error);
});
关于javascript - promise 问题 : Trying to wrap mysql queries to use it on NodeJS/Express，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/54996629/