我的目标是包装MySQL查询,将参数传递给函数,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
。我无法让这个功能正常工作。
我试过console.log(results)
。查询就像一个魅力。我唯一无法工作的是从外部函数中捕获结果。
有什么想法吗?提前致谢!
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。这样做
var cod_customer = 1;
var isexpired;
isExpired(cod_customer).then(function (results) {
isexpired = results;
console.log(isexpired);
}, function (error) {
console.log("Error: " + error);
});
你没有在selectOneField函数中返回promise,它必须返回promise并且你也不能这样做
rtf = db_.selectOneField('view_expiredusers','cod','cod',cod);
你将不得不使用async-await
必须以这种方式处理
//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_).then(function (results) {
return results;
}).catch(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).then(rtf => {
console.log(rtf);
return rtf;
});
};