I'm new to Firebase and am reading the docs to learn.
I am currently using Firestore instead of the Database and to be honest, I am not super sure about the pro / cons of each.
In their tutorials for reading and writing data to a Database they have the following code regarding transactions:
function toggleStar(postRef, uid) {
postRef.transaction(function(post) {
if (post) {
if (post.stars && post.stars[uid]) {
post.starCount--;
post.stars[uid] = null;
} else {
post.starCount++;
if (!post.stars) {
post.stars = {};
}
post.stars[uid] = true;
}
}
return post;
});
}
which is meant to mitigate race conditions / corruption to the variable stars in this case.
My question is what is the Firestore equivalent of transaction e.g.
import firebase from 'firebase'
const postId = 1
const firestorePostRef = firebase.firestore().collection('posts').doc(postId)
// throws an error that firestorePostRef.transaction is not defined
firestorePostRef.transaction( (post) => {
if (post) {
// ...
}
})
Firebase Firestore has the same functionality. Read data and at the same operation write over something like :
// Create a reference to the SF doc.
var sfDocRef = db.collection("cities").doc("SF");
db.runTransaction(function(transaction) {
return transaction.get(sfDocRef).then(function(sfDoc) {
if (!sfDoc.exists) {
throw "Document does not exist!";
}
var newPopulation = sfDoc.data().population + 1;
if (newPopulation <= 1000000) {
transaction.update(sfDocRef, { population: newPopulation });
return newPopulation;
} else {
return Promise.reject("Sorry! Population is too big.");
}
});
}).then(function(newPopulation) {
console.log("Population increased to ", newPopulation);
}).catch(function(err) {
// This will be an "population is too big" error.
console.error(err);
});
Here the related documents link
Related
I am trying to get data from an api using axios.
I am first getting the token, and then using the token to make the request. Since there is a limit on how much information can be responded, I have to use a while loop to get all the data and store it all to an empty array.
However, I am getting a bunch of 'undefined', I read other similar articles online with regard to this return, and most of them is because of "no return", but since I am using a while loop, where can I return the data?
const getDailySales = async (req, res) => {
try {
const res_token = await axios.post(
`https://cysms.wuuxiang.com/api/auth/accesstoken?appid=${process.env.TCSL_APPID}&accessid=${process.env.TCSL_ACCESSID}&response_type=token`
);
const token = res_token.data.access_token;
var list = [];
var pageTotal = true;
var pageNo = 1;
while (pageTotal) {
var salesData = await axios.post(
`https://cysms.wuuxiang.com/api/datatransfer/getserialdata?centerId=${process.env.TCSL_CENTERID}&settleDate=2022-09-30&pageNo=${pageNo}&pageSize=20&shopId=12345`
{},
{
headers: {
access_token: `${token}`,
accessid: `${process.env.TCSL_ACCESSID}`,
granttype: "client",
},
}
);
list.push(salesData);
console.log(salesData.data.data.billList.shop_name);
if (salesData.data.data.pageInfo.pageTotal !== pageNo) {
pageNo += 1;
} else {
pageTotal = false;
}
}
} catch (error) {
console.log(error);
}
};
Above implementation would work.
Return list just before catch and after ending of the while loop
} else {
pageTotal = false;
}
}
return list;
} catch (error) {
console.log(error);
}
};
Few suggestions
Use let/const instead of var.
Can elaborate more error handling
return list like this:
return res.status(200).json({list});
I have been getting this error for a couple of days. I am trying to calculate the necessary Slippage in PancakeSweap automatically.
For this I am trying different percentages and I call estimateGas to see if the transaction fails. But I only get the error
TransferHelper: TRANSFER_FROM_FAILED
I have tried a lot of methods and none of them work for me.
I'm sure the contract is approved and that it should work in the blockchain side. In pancakeswap it works for me, same wallet, same tokens and same amounts. I do not understand that it can fail.
const Web3 = require("web3");
const abi = require("./abi.json");
const web3 = new Web3("https://bsc-dataseed.binance.org/");
const contract = new web3.eth.Contract(abi, "0x10ed43c718714eb63d5aa57b78b54704e256024e");
function isValid(res) {
return new Promise((resolve, reject) => {
contract.methods.swapExactTokensForTokens(res[0], res[1], ["TOKEN_A", "TOKEN_B" ], "MI_WALLET", 1639969436 ).estimateGas(function(error, result) {
console.log(error.message)
if(error.message.includes("INSUFFICIENT_OUTPUT_AMOUNT")) {
console.log("Bad slippage")
reject()
}
else if(error) {
reject()
}
else {
resolve()
}
});
})
}
(async () => {
contract.methods.getAmountsOut("20000000000", ["TOKEN_A", "TOKEN_B" ]).call().then(async res => {
const data = res;
let slippage = 0;
while (true) {
try {
await isValid(data);
break;
}
catch(e) {
slippage++;
console.log(slippage / 100 * data[1])
let newS = data[1] - (slippage / 100 * data[1])
console.log(slippage, newS);
if(slippage == 20) {
break;
}
}
}
console.log(slippage)
})
})();
I am trying to build a simple Alexa Skill. Now, I want to access some of my slot values. This is my code. When I uncomment even the line that I define Alexa in, my skill will not work. Also, if I only uncomment the line defining var text, I still get "there was a problem with the skills response". Const gives the same output. I am using custom slots called recipe. How can I access the slots in my lambda function? Thanks.
const breakfast = {
"bacon and eggs":["bacon","egg"],
"buttered toast":["bread", "butter"]
};
const lunch = {
"ham sandwich":["ham","cheese"]
};
const dinner = { "Steak and eggs": ['steak','eggs']};
//const Alexa = require('ask-sdk-core');
exports.handler = (event, context, callback) => {
try {
if (event.request.type === 'LaunchRequest') {
callback(null, buildResponse('Hello from Lambda'));
} else if (event.request.type === 'IntentRequest') {
const intentName = event.request.intent.name;
if (intentName === 'breakfast') {
callback(null, buildResponse(Object.keys(breakfast)+"") );
}
else if (intentName === 'lunch') {
callback(null, buildResponse(Object.keys(lunch)+"") );
}
else if (intentName === 'dinner') {
callback(null, buildResponse(Object.keys(dinner)+"") );
}
else if (intentName ==='requestRecipe'){
//var text = this.event.request.intent.slots.recipe.value;
//const meal = Alexa.getSlotValue(intentName, "meal")
callback(null, buildResponse("Recipe requested") );
}
else {
callback(null, buildResponse("Sorry, i don't understand"));
}
} else if (event.request.type === 'SessionEndedRequest') {
callback(null, buildResponse('Session Ended'));
}
} catch (e) {
context.fail(`Exception: ${e}`);
}
};
function buildResponse(response) {
return {
version: '1.0',
response: {
outputSpeech: {
type: 'PlainText',
text: response,
},
shouldEndSession: false,
},
sessionAttributes: {},
};
}
for a bit of context: my lambda has the endpoint of what my alexa hosted skill was, and the alexa skill has the endpoint of the lambda. when I say const gives the same output, i mean instead of using var, when I use const, it does the same thing. The JSON file that i get as a reply is empty brackets.
I found the issue behind my problem. Instead of using
//var text = this.event.request.intent.slots.recipe.value;
i simply did var text = event.request.intent.slots.recipe.value; I am now able to use text in building a response or something like that.
I`m trying to query my business network using buildQuery but it always returns an empty array.
My code is as follows.
This is the connection.js file:
module.exports = {
BusinessNetworkConnection : require('composer-client').BusinessNetworkConnection,
cardName : '',
connection: {},
connect : function() {
var cardType = { type: 'composer-wallet-filesystem' }
this.connection = new this.BusinessNetworkConnection(cardType);
return this.connection.connect(this.cardName);
},
disconnect : function(callback) {
this.connection.disconnect();
}
};
This is my query.js file which being invoked to get results:
const connection = require('./connection');
const getContacts = async (cardName,companyID) => {
connection.cardName = cardName;
try {
await connection.connect();
main();
} catch (error) {
main(error);
}
async function main(error) {
if (error) { return new Error("Ops Error: ",error) };
const statement = 'SELECT org.finance.einvoice.participant.Company WHERE (participantId == _$companyID)'
const query = await connection.connection.buildQuery(statement);
const company = await connection.connection.query(query, { companyID }).catch(err => {return new Error(err)});
await connection.connection.disconnect().catch(err => new Error(err));
console.log(company);
return company;
};
};
module.exports = {
getContacts
};
The expected behavior from getContacts() is to return an asset from business network but it actually returns an empty array.
Current versions: composer-cli 0.20 , composer-playground 0.20 , composer-client 0.20 , composer-common 0.20 and fabric-dev-server 1.2 .
i found the solution for this issue.
i was using card which was not allowed to perform queries. However, when i used the admin card it returned with results.
other way is to allow participants to issue queries in permission.acl file.
I have this block of code in a function:
this.apiService.fetchCategories(!this.cacheData).subscribe(
response => {
if(this._jsnValService.valCategories(response)) {
this.customerMap.categories = this.formatCategories(response["categories"]);
} else {
alert("Categories failed the schema validation. Please contact support if this happens again.");
}
},
error => {
this.notification.title = "Oops, there's a problem.";
this.notification.content = "Seems there's an issue getting the provider categories.";
this.notification.show("provider_categories_api");
}
);
It fetches some data and then runs a validation on the data (if(this._jsnValService.valCategories(response)) {).
However, my validation of the data is actually async too, because it validates it against a json schema which is in a seperate json file so it has to read the file first.
I have used a promise to read the file contents and then do the validation:
#Injectable()
export class ValidateJSONSchemaService {
constructor(private http: Http) {}
public valCategories(json) {
this._getSchema("./jsonSchema.categories.json").then((schema) => {
this._valSchema(json, schema);
});
};
private _valSchema(json, schema): any {
var ajv = new Ajv();
var valid = ajv.validate(schema, json);
if (!valid) {
console.log(ajv.errors);
return false;
} else {
console.log(valid);
return true;
};
};
private _getSchema(fileName): any {
return new Promise((resolve, reject) => {
this.http.get(fileName)
.map(this._extractData)
.catch(this._handleError)
.subscribe(schema => resolve(schema));
});
};
private _extractData(res: Response) {
let body = res.json();
return body.data || {};
};
How can I edit the top code block in this question to account for the asynchronous function inside the if statement (if(this._jsnValService.valCategories(response)) {)?
if you are using ES6 you could use async/await like this:
async function _validateCategories() {
this.apiService.fetchCategories(!this.cacheData).subscribe(
response => {
const valid = await this._jsnValService.valCategories(response)
if(valid) {
this.customerMap.categories = this.formatCategories(response["categories"]);
} else {
alert("Categories failed the schema validation. Please contact support if this happens again.");
}
},
error => {
this.notification.title = "Oops, there's a problem.";
this.notification.content = "Seems there's an issue getting the provider categories.";
this.notification.show("provider_categories_api");
}
);
}
if not, your function fetchCategories should return a promise or allow you to pass a callback to do something like this:
async function _validateCategories() {
this.apiService.fetchCategories(!this.cacheData).subscribe(
response => {
this._jsnValService.valCategories(response).then((error, valid)=> {
if(error) {
alert("Categories failed the schema validation. Please contact support if this happens again.");
}
this.customerMap.categories = this.formatCategories(response["categories"]);
})
},
error => {
this.notification.title = "Oops, there's a problem.";
this.notification.content = "Seems there's an issue getting the provider categories.";
this.notification.show("provider_categories_api");
}
);
}