I have a requirements that some functions should be called after some method completes execution.
Below is my code of processing the queue.
processQueue() {
while (this.queue.length) {
var item = this.queue.shift();
item.resolve(item.func(item.types));
}
}
This is one of the sample function to push method in queue
getAllValues() {
let promise1 = new Promise((resolve, reject) => {
if (this.isReady) {
resolve(this._getAllValues());
} else {
this.queue.push({
resolve: resolve,
func: this._getAllValues
});
}
});
return promise1;
}
And this is one of the function which will be called on processing the queue
_getAllValues() {
var results = {}, values = this.enumInstance.enumsCache.values;
for (var type in values) {
if (values.hasOwnProperty(type)) {
results[type] = values[type][this.enumInstance.lang];
}
}
return results;
}
The issue i am facing is when i call _getAllValues() directly then i am able to access this.enumInstance.
But when same method is being accessed through processQueue() i am unable to access this.enumInstance. It gives me undefined. I think this is not referred to main class in this case.
So can anyone help me here. How can i resolve this?
Related
I am trying to create a design for tags of entities in PouchDB with ReactJS. I managed to save my design using the put function, but when I query my design, the response is just an empty array and I am getting following error in console:
TypeError: Cannot read property 'emit' of undefined
I think the problem is in my function that I later use as a map parameter to my design variable:
function emitTagsMap(doc)
{
if (doc !== undefined)
{
if (Array.isArray(doc.tags))
{
doc.tags.forEach(x =>
{
/* Here is probably the problem - this.db is undefined */
this.db.emit(x, null);
});
}
}
};
this.db is declared in constructor:
constructor(service, name)
{
if (!service || !name) throw new Error("PouchDatabase initialized incorrectly");
this.name = name;
this.db = new PouchDB(name);
this.service = service;
this.tagsView();
}
Please bare in mind that I am completely new to PouchDB.
Any ideas how can I initialize the emit function?
Thank you in advance.
I assume, that your function is a part of a JavaScript class (otherwise you have to explain the idea with this). In ES6, you have to bind this to your regular functions. You have two options:
First - bind it via constructor:
constructor() {
this.emitTagsMap = this.emitTagsMap.bind(this);
}
Second - declare the function as an arrow one. This way, react will bind it for you:
emitTagsMap = (doc) =>
{
if (doc !== undefined)
{
if (Array.isArray(doc.tags))
{
doc.tags.forEach(x =>
{
/* Here is probably the problem - this.db is undefined */
this.db.emit(x, null);
});
}
}
};
You don't need to call emit over the database object.
Try this:
function emitTagsMap(doc)
{
if (doc !== undefined)
{
if (Array.isArray(doc.tags))
{
doc.tags.forEach(x =>
{
emit(x, null);
});
}
}
};
According to the PouchDB docs a design document is formed like this:
// first create a new design doc and pass your map function as string into it
var ddoc = {
_id: "_design/my_index",
views: {
by_name: {
map: "function (doc) { if (doc !== undefined) { if (Array.isArray(doc.tags)) { doc.tags.forEach(x => { emit(x, null); }); } } }"
}
}
};
// save it
db.put(ddoc).then(function () {
// success!
}).catch(function (err) {
// some error (maybe a 409, because it already exists?)
});
//Then you actually query it, by using the name you gave the design document when you saved it:
db.query('my_index/by_name').then(function (res) {
// got the query results
}).catch(function (err) {
// some error
});
https://pouchdb.com/guides/queries.html
I am unable to do the promise looping.
I make a service call to get list of providers, then for each provider, I make another service call to get a customer.
A provider has 1 or more customers. So eventual list of customer is to be decorated and displayed.
In other format I am trying to achieve:
*serviceA.getProvider(){
foreach(providers){
foreach(provider.customerID){
serviceB.getCustomer(customerId)
}
}
}
.then(
foreach(Customer){
updateTheCustomer;
addUpdatedCustomerToAList
}
displayUpdatedCustomreList();
)*
I have written following code, that isn't working
doTheJob(model: Object) {
let A = [];
let B = [];
let fetchP = function(obj) {
obj.Service1.fetchAllP().then(function (response) {
let P = cloneDeep(response.data);
_.forEach(P, function(prov) {
_.forEach(prov.CIds, function(Id) {
A.push(Id);
});
});
_.forEach(A, function(CId) {
return obj.Service2.getById(CId);//what works is if this statement was: return obj.Service2.getById(A[0]);
//So, clearly, returning promise inside loop isn't working
});
})
.then(function(response) {
B.push(response.data); //This response is undefined
angular.forEach(B, function (value) {
obj.updateAdr(value)
});
obj.dispay(B);
});
};
fetchP(this);
}
forEach don't stop when you use return inside of it, try to use a plain loop instead, why you don't just loop with for ?
_.forEach(A, function(CId) {
return obj.Service2.getById(CId);
}
as stated by #Ze Rubeus if you return inside a callback within a for loop that value will be lost, since it's not returned to the caller.
probably you wanted something like this
return Promise.all(A.map(function(CId){
//collect each promise inside an array that will then be resolved
return obj.Service2.getById(CId);
})
Trying to cut down code repetition, I've set up a $firebaseArray extension as follows:
var listUsersFactory = $firebaseArray.$extend({
$$added: function (snap) {
return new Customer(snap);
},
$$updated: function (snap) {
var c = this.$getRecord(snap.key);
var updated = c.updated(snap);
return updated;
},
});
and the Customer code:
function Customer(snap) {
this.$id = snap.key;
this.updated(snap);
}
Customer.prototype = {
updated: function(snap) {
var oldData = angular.extend({}, this.data);
this.data = snap.val();
// checks and such
}
}
This works wonders when loading, showing and saving a list of customers, and I'm satisfied with it.
Now, the problem lies in retrieving a single customer and its detail page, because the Customer object isn't an extension of $fireObject and is therefore lacking a $save method
Single customer loading:
customersRef.once("value", function(snapshot) {
if(snapshot.child(uuid).exists())
{
customersFactory.customerDetails = new Customer(snapshot.child(uuid));
return deferred.resolve();
}
}
but when I call customersFactory.customerDetails.$save() I get an error
How can I extend my class so that it works for both array and single object uses?
I couldn't find a way to do this, so I ended up using the $firebaseArray and getting single records off that to pass as details, in case anyone's wondering
Any ideas? Why does node say 'filename is undefined'? Thanks.
Contract, policy ans invoice functions resolve with no data, just resolve().
var dc = function(data) {
return new Promise(function(resolve, reject) {
var filename = 'Test';
var contract = function() { ... }
var policy = function() { ... }
var invoice = function() { ... }
contract().then(invoice().then(policy().then(function() {
console.log(filename); // Test
resolve(filename); // UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): ReferenceError: filename is not defined
})))
})
}
First of all, you cannot write:
contract().then(invoice() ... )
(that would work if the invoice() function returned another function to act as a then handler)
You have to write:
contract().then(function (value) { invoice() ... })
Or:
contract().then(value => invoice() ... )
Or maybe this if one function should handle the result of other function:
contract().then(invoice).then(policy).then(function (result) { ... });
What you have to pass as an argument to then is a function, not a result of calling a function (which is probably a promise in your example).
I don't know if that's the only problem with your approach but it is certainly one of the problems. Of course it may work but probably not how you expect.
2017 Update
If you use ES2017 async/await that's available in Node since v7.0 then instead of:
contract().then(invoice).then(policy).then((result) => { ... });
you can use:
let a = await contract();
let b = await invoice(a);
let c = await policy(b);
// here your `result` is in `c`
or even this:
let result = await policy(await invoice(await contract()));
Note that you can only use it in functions declared with the async keyword. This works on Node since version 7. For older versions of Node you can use a similar thing with a slightly different syntax using generator-based coroutines, or you can use Babel to transpile your code if that's what you prefer of if that what you already do.
This is quite a new feature but there are a lot of questions on Stack Overflow about it. See:
try/catch blocks with async/await
Do async in a blocking program language way?
try/catch blocks with async/await
Use await outside async
Using acyns/await in Node 6 with Babel
When do async methods throw and how do you catch them?
using promises in node.js to create and compare two arrays
Keeping Promise Chains Readable
function will return null from javascript post/get
It looks like you don't care about the order, in which case you could use Promise.all. Does this work for you? It will resolve once all of the promises have been resolved, or it will reject as soon as any one of them rejects.
function contract(data) { return new Promise(...) }
function policy(data) { return new Promise(...) }
function invoice(data) { return new Promise(...) }
function dc(data) {
var filename = 'Test';
return new Promise(function(resolve, reject) {
Promise.all([contract(data), policy(data), invoice(data)]).then(
function (values) {
console.log(filename);
resolve(filename)
},
function (err) {
reject(err);
}
);
});
}
If you care about the order, then you do have to chain them, like you've tried to do. You're code is passing promises as an argument to then. You need to pass functions.
function contract(data) { return new Promise(...) }
function policy(data) { return new Promise(...) }
function invoice(data) { return new Promise(...) }
function dc(data) {
var filename = 'Test';
return new Promise(function(resolve, reject) {
contract(data).then(
function (contract_res) {
policy(data).then(
function (policy_res) {
invoice(data).then(
function (invoice_res) {
console.log(filename);
resolve(filename);
},
function (err) { reject(err); } // invoice promise rejected
);
},
function (err) { reject(err); } // policy promise rejected
);
},
function (err) { reject(err); } // contract policy rejected
);
});
}
You may be able to simplify this with catch, but the deep nesting is a pain. Take a look at this post about flattening Promise chains.
I am going through John Papa's SPA course on pluralsight and I am running into error that say The 'structuralTypeName' parameter must be a 'string' while using breeze. Here is the actual error that is being thrown
The code that is generating this error is metadataStore.getEntityType:
function extendMetadata() { names
var metadataStore = manager.metadataStore;
var types = metadataStore.getEntityType();
types.forEach(function(type) {
if (type instanceof breeze.EntityType) {
Set(type.shortName, type)
}
});
function set(resourceName, entityName) {
metadataStore.setEntityTypeForResourceName(resourceName, entityNames);
}
it is called by my prime function.
function prime() {
if (primePromise) return primePromise //if primePromise was loaded before, just return it
primePromise = $q.all([getLookups()])
.then(extendMetadata)
.then(success);
return primePromise;
function success() {
setLookups();
log('Primed the data');
}
I'm unsure what the problem is with the breeze call. Any insight into how to fix this? Thanks for your help community.
Nick
Here is the lookups query info:
function setLookups() {
var entityNames = {
personnel: 'Personnel',
cto: 'Cto',
kkeys: 'Kkey',
promotion: 'Promotion',
loa: 'Loa'
};
service.lookupCachedData = {
ctos: _getAllLocal(entityNames.cto, 'ctodate' )
kkeys: _getAllLocal(entityNames.kkeys, 'keystamp'),
promotions: _getAllLocal(entityNames.promotion, 'pdate'),
loas: _getAllLocal(entityNames.loa, 'lstrdte')
}
}
function _getAllLocal(resource, ordering) {
return EntityQuery.from(resource)
.orderBy(ordering)
.using(manager)
.executeLocally();
}
function getLookups() {
return EntityQuery.from('Lookups')
using(manager).execute()
.then(querySucceeded, _queryFailed)
function querySucceeded(data) {
log('Retrieved [Lookups] from remote data source', data, true);
return true;
}
}
function _queryFailed(error) {
var msg = config.appErrorPrefix + 'Error retrieving data from entityquery' + error.message;
logError(msg, error);
throw error;
}
You have to pass in a string to getEntityType. Sorry I missed that the first time through.
metadataStore.getEntityType('cto');
Also you are going to blow up when you are trying to call Set() function but the functions name is set() and also set is probably a keyword you aren't trying to override.