I am getting an error trying to call an existing smart contract function using call().
The error is "Returned values aren't valid, did it run Out of Gas? You might also see this error if you are not using the correct ABI for the contract you are retrieving data from, requesting data from a block number that does not exist, or querying a node which is not fully synced." My code is below
let url = 'https://api.etherscan.io/api?module=contract&action=getabi&address=0x672C1f1C978b8FD1E9AE18e25D0E55176824989c&apikey=<api-key>';
request(url, (err, res, body) => {
if (err) {
console.log(err);
}
let data = JSON.parse(body);
let contract_abi = JSON.parse(data.result);
let contract_address = '0x672C1f1C978b8FD1E9AE18e25D0E55176824989c';
const contract = new web3.eth.Contract(contract_abi, contract_address);
contract.methods.totalSupply().call()
.then(result => {
console.log('result', result);
}).catch(err => {
console.log('error: ', err);
})
})
When I execute the same function using send() it works, however I need the return value of the function which is why I want to use call(). I am using ganache to set up a local test network which is working fine. Thanks!
Related
I want to get this functionality if(thereIsSomeError) //stop executing further. for example if there some error accurs in middleware or in the callback then i don't want to execute callback(in the app.route) and the middleware further
I tried this code. But i'm still getting req.err as true. how can i fix this issue
// My MiddleWare
export let Middleware=()=> {
return (req,res,next)=>{
next()
console.log(req.err) // Problem is here.. i'm still getting req.err(true)
if(!req.err){
db.query(`query`,(error, responseData)=>{
if(error) console.log(error)
db.query(`second query`,{...// send data to the
database})
})
}
}
}
//End point
app.post('/addStudent',Middleware, (req, res) => {
//setting error to true initially
req.err=true;
let data = req.body
db.query(`query `, data.username, (err, d) => {
if (err) return res.json(err)
else {
// since no Error accured so set the error to false
req.err=false;
let q = 'query';
let values = {//data here}
db.query(q, values, (err, data) => {
if (err) return res.status(200).json(err)
else return res.status(200).json({ data })
})
}
})
})
First, a middleware runs BEFORE a request, NOT AFTER. If you set req.err = true in your POST endpoint, IT WILL STAY TRUE, meaning your database call will certainly return an error.
Second, to successfully abort a middleware call, use return. Returning a function stops it immediately. You can choose either to return next(err) to forward the error to the handler, or to use return res.send('Error') to terminate the response in the middleware.
I have some raw json that I'm trying to send to my back end server in mysql. I'm currently trying to loop through the specific array in the json that I need and sending data from each of the children in the array via a POST request but I am getting "Cannot set headers after they are sent to the client".
app.post('/reddit-import', function (req, res) {
console.log("Route /reddit-import POST");
let data = req.body.data.children
data.forEach(child => {
let sql1 = `CALL insert_user('${child.data.author}',
'${child.data.author_fullname}');`
connection.query(sql1,
data,
function (errQuery, result) {
if (errQuery) {
console.log(errQuery);
res.json({status: "Error", err: errQuery});
res.end();
} else {
console.log("Insert ID: ", result.insertId);
res.json({status: result.insertId, err: ""});
res.end();
}
}
);
When I send the POST request, my backend gets 2 rows of data before it hits me with the error message...any ideas?
You seem to be ending your outer response in the data.forEach with a res.end(), which I’m assuming is used to indicate the end of the outer HTTP request to the client. Did you perhaps mean to use “result” there instead?
Try this if you need to keep track insert IDs:
app.post('/reddit-import', function(req, res) {
console.log("Route /reddit-import POST");
let data = req.body.data.children
const insertIds = data.map(child => {
return new Promise((resolve, reject) => {
const sql = `CALL insert_user('${child.data.author}', '${child.data.author_fullname}')`;
connection.query(sql, (err, result) => {
if (err) {
console.log(err);
return reject(err);
}
console.log("Insert ID: ", result.insertId);
return resolve(result.insertId);
});
});
});
return Promise.all(insertIds)
.then(ids => {
return res.json({
insertIds: ids
});
})
.catch(err => {
return res.status(500).json({
message: 'got query error'
});
});
});
What this basically does is that on each query, you keep track of the insert IDs. We need to use Promises because the query() function is asynchronous, meaning it runs independently and there's no other way to keep track of the data outside of its function(err, result) callback. Now we have an array of Promises which contains the insert IDs, and what's left is to send a response that this is successful. And in order to do that, we can't simply do res.json(insertIds) because insertIds is an array of Promises and we still need to extract the values. We can easily extract all data at once from an array of Promises by using Promise.all(insertIds).then(ids => ...). If you wish to send a response informing that the request is successful, do so in this then callback. Lastly and most importantly, we handle errors in a Promise chain's .catch() block. This is where you want to send a response informing the client that there are errors.
Some things that we can improve from this solution is to implement rollbacks in case we have errors, and of course validations of parameters. Unfortunately I have to leave this to the OP to implement.
Also, keep in mind you should only send a response once and only once each request.
I'd like to create api call from back-end for DELETE query from mysql DB but when execute it in browser get error
'Cannot GET ...'
I pass into the route id of row which had got from DB
At back-end the code is:
app.delete('/products/delete/:id*?', function(req, res) =>{
let { id } = req.query;
let DELETE_PRODUCT_FROM_DB = `DELETE FROM my_db.products WHERE my_db.id= '${req.query}'`;
console.log("id: ", req.query);
// delete a row with id = req.query
connection.query(DELETE_PRODUCT_FROM_DB, (error, results, fields) => {
if (error) return console.error(error.message);
res.status(200).send(results);
console.log("Deleted Row(s):", results.affectedRows);
});
});
But finally this call not works and row not deleted
let DELETE_PRODUCT_FROM_DB = `DELETE FROM my_db.products WHERE my_db.id= '${req.query.id}'`;
console.log("id: ", req.query.id);
Try using this.
fetch(url, {
method: 'delete'
}).then(response => response.json());
Try running this in your browser console. It should work.
Most likely you're making a GET call to a DELETE resource.
Please read Express 4.x. Can you share the code you're using to make DELETE request from browser?
I did some changes and now running version of the code looks like
app.delete('/products/delete/:id', (req, res) => {
let { id } = req.params ;
let DELETE_PRODUCT_FROM_DB = `DELETE FROM my_DB.products WHERE id= '${id}'`;
console.log('id: ', req.params);
// delete a row with id = req.params
connection.query(DELETE_PRODUCT_FROM_DB, (error, results, fields) => {
if (error) return console.error(error.message);
res.status(200).send(results);
console.log('Deleted Row(s):', results.affectedRows);
});
});
Also, I figured out that changes from req.query on req.params helped to get id from the link as a parameter
I am wondering what the proper way is to make a server response in a NodeJS Express app when an internal server error occurs. Here is some simplified code for registering users. The main issue being, if an internal server error happens, I want to log the error, but also respond to the client with a different message. What I have below is what my current solution is, but I feel like I'm not doing it properly (or not following the conventional way). I currently have an async waterfall setup which is called from the route.
//Controller.js
function verifyInputs(user, resCallback, callback) {
//verify user inputs (ie. passwords match)
if (valid) {
callback(null)
} else {
resCallback('whatever was wrong with inputs', 409)
callback('ok')
}
}
function checkIfUserExists(user, resCallback, callback) {
db.getPool().getConnection((err, connection) => {
if (err) {
resCallback('custom response error message', 500)
callback(err)
return
}
var sql = 'SELECT...'
connection.query(sql, (err, results) => {
connection.release()
if (err) {
resCallback('another custom response error', 500)
callback(err)
return
}
if (results.length > 0) {
resCallback('user already exists')
callback('ok')
}
})
)
}
module.exports.registerNewUser(user, callback) {
async.waterfall([
async.apply(user, callback, verifyInputs),
async.apply(user, callback, checkIfUserExists)
],
function(err, reults) {
if (err === 'ok') return
//log error or whatever here
})
}
This register function is called from the routes function:
//Router.js
router.post('/register', (req, res, next) => {
var newUser = //get user data from req
controller.registerNewUser(newUser, (msg, statusCode) => {
res.statusCode(statusCode)
res.send(msg)
})
})
The code above shows how I log the error while responding to the client with a different message. Is this the right or an OK way to do this?
Or maybe I shouldn't use a waterfall at all for this, and do something like this which would give me access to the res object at all stages without multiple callbacks:
router.post('/register', verifyInputs(), checkIfUserExists(), (req, res, next) => {
var newUser = //get user data from req
controller.registerNewUser(newUser, (msg, statusCode) => {
res.statusCode(statusCode)
res.send(msg)
})
})
I'm relatively new to server back end programming, and I am new to NodeJS and Express. I just want to make sure what I am doing the proper.
I am working on an Express App with MongoDB and trying to utilize FeathersJS for all my services. Here I'm running a test try to get an error message from the server to the client, but I have an issue with the response from the error handler. My req headers have the correct application/json stuff, so I assumed the Error Handler should send valid json back.
I know I'm not using the next callback in my function, but when I try to do that it gives the same error, so I'm thinking it has to do with the Error Handler. Any direction here would be greatly appreciated!
The first error log is on the server, which is correct.
Bucket Services
error >>>>> Bucket validation failed
Possibly Unhandled Rejection: Bucket validation failed, Promise { <rejected> 'Bucket validation failed' }
>>>>>> Error: Unexpected token < in JSON at position 0
at convert (/Users/jaruesink/Documents/Projects/Buckets/node_modules/feathers-rest/node_modules/feathers-errors/lib/index.js:365:79)
at toError (/Users/jaruesink/Documents/Projects/Buckets/node_modules/feathers-rest/lib/client/base.js:24:37)
at process._tickCallback (internal/process/next_tick.js:103:7)
my create function within the BucketService class:
create({
amount,
isFund = false,
name,
type,
userID: owner
}, params, next) {
const new_bucket = new Bucket({ name, amount, type, isFund, owner });
return new_bucket.save((error) => {
console.log('error >>>>>', error.message);
if (error) { return Promise.reject(error.message); }
return Promise.resolve(new_bucket);
});
}
my router file:
const feathers = require('feathers');
const errorHandler = require('feathers-errors/handler');
const rest = require('feathers-rest');
const router = feathers();
const LoginService = require('../services/login_service');
const UserService = require('../services/user_service');
const BucketService = require('../services/bucket_service');
// Enable REST services
router.configure(rest());
router.use((req, res, next) => {
res.header('Access-Control-Allow-Origin', '*');
res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept');
next();
});
router.use('/login', new LoginService());
router.use('/user', new UserService());
router.use('/bucket', new BucketService());
// Set up error handling
router.use(errorHandler());
module.exports = router;
I figured it out, the key was to correctly pass through a callback (next) function as the third parameter to handle errors. FeathersJS handles the Promise Rejections for you on errors. Then in my test I needed to convert the Feathers-Error to JSON before I could get the message.
I changed my test to:
it('can validate an incorrect bucket', (done) => {
const invalid_bucket = {
name: 'Invalid Bucket',
};
bucket_service.create(invalid_bucket, {}, (error) => {
error = error.toJSON();
assert(error.message.length > 0);
done();
});
});
and my create function to:
create({
amount,
isFund = false,
name,
type,
userID: owner
}, params, next) {
const new_bucket = new Bucket({ name, amount, type, isFund, owner });
return new_bucket.save()
.then(created_bucket => Promise.resolve(created_bucket))
.catch(next);
}