我正在尝试创建一个专注于唯一用户名的用户帐户创建脚本-池中的前缀和后缀,现有用户名列表以及保留用户名列表。
这只是开始(还没有保存!),已经需要三个连接,所以我只是决定看看我是否可以编写一个可以处理所有功能的函数。
到目前为止,这是我的代码-它位于 AWS Lambda 上,并通过 API网关进行了测试,如果有什么意思,
const dbConnMysql = require('./dbController');
var methods = {
createUser: function() {
let getPrefixSuffixList = new Promise((resolve, reject) => {
let connection = dbConnMysql.createConnection();
dbConnMysql.startConnection(connection)
.then((fulfilled) => {
let table = 'userNamePool';
return dbConnMysql.selectFrom(connection, table, '*', null);
})
.then((fulfilled) => {
console.log(fulfilled);
return dbConnMysql.closeConnection(connection)
.then((fulfilled) => {
resolve(fulfilled);
});
})
.catch((error) => {
console.log(error);
reject(error);
});
});
let getTempUserNameList = new Promise((resolve, reject) => {
// Same as getPrefixSuffixList, different table
});
let getRealUserNameList = new Promise((resolve, reject) => {
// Same as getPrefixSuffixList, different table
});
return new Promise((resolve, reject) => {
Promise.all([getPrefixSuffixList, getTempUserNameList, getRealUserNameList])
.then((fulfilled) => {
console.log(fulfilled[0]);
console.log(fulfilled[1]);
console.log(fulfilled[2]);
let response = {
"statusCode": 200,
"headers": {"my_header": "my_value"},
"body": {"Prefix Suffix":fulfilled[0], "Temp UserName List":fulfilled[1], "Real UserName List":fulfilled[2]},
"isBase64Encoded": false
};
resolve(response);
})
.catch((error) => {
let response = {
"statusCode": 404,
"headers": {"my_header": "my_value"},
"body": JSON.stringify(error),
"isBase64Encoded": false
};
reject(response);
})
});
}
};
module.exports = methods;
此功能在index.js
的其他地方调用:
app.get('/createUserName', function (req, res) {
var prom = Register.createUser();
prom.then((message) => {
res.status(201).json(message);
})
.catch((message) => {
res.status(400).json(message);
});
})
现在我不能完全确定我对Promise.All所做的一切是否正确,但是据我所知,如果一个承诺失败,Promise.All也会失败。
但是,个人承诺确实可以很好地工作,并从数据库中注销相应的结果。但是在Promise.All内部,所有内容都只注销了undefined
。
有什么我想念的吗?
答案 0 :(得分:2)
问题的原因是这样的。您需要运行函数,这些函数然后返回最终将解决的promise:
Promise.all([getPrefixSuffixList(), getTempUserNameList(), getRealUserNameList()])
这里还有一些更简单的代码。通常,不需要new Promise()
。此代码可能会解决其他问题。另外,undefined
可以从代码的任何部分进行打印,请确保将其打印在您认为合适的位置。
// Dummy MySQL connector
const dbConnMysql = {
createConnection: () => 'Connection',
startConnection: conn => new Promise(resolve => setTimeout(resolve, 100)),
selectFrom: (conn, t, q, n) =>
new Promise(resolve =>
setTimeout(() => {
console.log(`${conn}: SELECT ${q} FROM ${t}`);
resolve(`x ${t} RECORDS`);
}, 100)
),
closeConnection: conn => new Promise(resolve => setTimeout(resolve, 100)),
};
const methods = {
createUser() {
const getPrefixSuffixList = () => {
const connection = dbConnMysql.createConnection();
return dbConnMysql
.startConnection(connection)
.then(() => {
const table = 'userNamePool';
return dbConnMysql.selectFrom(connection, table, '*', null);
})
.then(fulfilled => {
console.log(fulfilled);
return dbConnMysql.closeConnection(connection).then(() => fulfilled);
})
.catch(error => {
console.log(error);
// Note: this catch will stop the error from propagating
// higher, it could also be the cause of your problem.
// It's okay to catch, but if you want the error to
// propagate further throw a new error here. Like this:
throw new Error(error);
});
};
const getTempUserNameList = () => {
// Same as getPrefixSuffixList, different table
};
const getRealUserNameList = () => {
// Same as getPrefixSuffixList, different table
};
return Promise.all([getPrefixSuffixList(), getTempUserNameList(), getRealUserNameList()])
.then(fulfilled => {
console.log('fulfilled[0]: ', fulfilled[0]);
console.log('fulfilled[1]: ', fulfilled[1]);
console.log('fulfilled[2]: ', fulfilled[2]);
return {
statusCode: 200,
headers: { my_header: 'my_value' },
body: {
'Prefix Suffix': fulfilled[0],
'Temp UserName List': fulfilled[1],
'Real UserName List': fulfilled[2],
},
isBase64Encoded: false,
};
})
.catch(error => ({
statusCode: 404,
headers: { my_header: 'my_value' },
body: JSON.stringify(error),
isBase64Encoded: false,
}));
},
};
methods.createUser();