node.js - Using Promise with CouchDB nano & forEach -


i need debugging code/or learn efficient way it- tried using bluebird.each capture executions within foreach, didn't work. same setting new promise pure javascript. need how execute foreach first , move on. 

let arr = [];  let fields = ['environment', 'habitat', 'earth] promise.each(fields, field => {   nano.db.use(field).view('options', 'options')     .spread((body, header) => {       arr.push(body.rows);   }) }).then(() => console.log(arr))

-expected outcome: arr console.log ====> [1,2,3,4,5]

-actual outcome: arr empty array ====> [ ]

i see it's problem asynchronicity, can't seem figure out how make work. input or resources appreciated!

thank you

i haven't ran code sorry if i'm incorrect, looking @ , bluebird docs assume correction need make return nano.db call wrapped in promise inside promise.each

let arr = [];  let fields = ['environment', 'habitat', 'earth'] promise.each(fields, field => {   return new promise ((resolve, reject) => {     nano.db.use(field).view('options', 'options')       .spread((body, header) => {         arr.push(body.rows);         resolve();       })   }); }).then(() => console.log(arr))

i believe assumption right you're having problem asynchronicity when getting empty array instead of expect. i'm assuming .then method firing before nano.db gets data.

i wrapped call of nano.db in promise await nano.db finishing since promise.each supports returning promises inside it.

bluebird's promise docs state promise.each.

if iterator function returns promise or thenable, result of promise awaited before continuing next iteration.

so, if promise not returned in promise.each , asynchronous happens inside then or catch method on promise under same circumstances.

as not know bluebird there may way change promise more bluebird like. promise wrapped around nano.db call normal es6 promise bluebird may or may not have different api creating promises.


Comments

Post a Comment

Popular posts from this blog

c# - Update a combobox from a presenter (MVP) -

i using mvp in project, new in mvp. have 2 comboboxes. when select option in combobox, combobox should filled new data. this action in presenter. view 'view1' in presenter, , introduced combobox1 , combobox2 properties in 'view1', because need 'datasource', 'displaymember', 'valuemember' , 'refresh()' in method below. but, when using pattern, enough send property like public string combobox2 { { return combobox1.selectedvalue.tosstring(); } } into presenter not whole combobox. how can solve problem? public void onselectedindexchangedcombobox1() { if (view1.combobox1.selectedindex == -1) { return; } datatable dt = tools.getdatatable("a path"); var query = (from o in dt.asenumerable() o.field<string>("afield") == farmerview.combobox1.selectedvalue.tostring() orderby o.field<string>("anotherfield") select...
Read more

How to understand 2 main() functions after using uftrace to profile the C++ program? -

i trying uftrace profile following simple c++ program: #include <iostream> class { public: a() {std::cout << "a created" << std::endl;} ~a() {std::cout << "a destroyed" << std::endl;} }; int main() { a; return 0; } the profile result this: # uftrace a.out created destroyed # duration tid function 2.026 [ 4828] | __cxa_atexit(); [ 4828] | main() { [ 4828] | __static_initialization_and_destruction_0() { 89.397 [ 4828] | std::ios_base::init::init(); 0.768 [ 4828] | __cxa_atexit(); 93.029 [ 4828] | } /* __static_initialization_and_destruction_0 */ 94.425 [ 4828] | } /* main */ [ 4828] | main() { [ 4828] | a::a() { 11.104 [ 4828] | std::operator <<(); 10.825 [ 4828] | std::basic_ostream::operator <<(); 24.514 [ 4828] | } /* a::a */ [ 4828] | a::~a() { 0.978 [ 4828] | ...
Read more

How to put a lock and transaction on table using spring 4 or above using jdbcTemplate and annotations like @Transactional? -

i trying put lock on table while writing on table , if happened in between roll-back . trying convert below code lock table test_g1 read; lock table test_g write; -- begin; start transaction; insert test_g1 values(143); insert test_g values(145); select * test_g1; select * test_g; rollback; select * test_g; unlock tables; how convert above code @transactional spring jdbctemplate code? @transactional(rollbackfor={dataaccessexception.class}) public void test(){ jdbctemplate.execute("insert test1 (id, nam) values (4, 'a')"); throw new dataaccessexception("error") { }; } here trying throw error, insert statement should rollback it's not happening . thanks edit-1 attaching code , doing in jdbcdaoimpl.java , mentioned problem comment above test() . app.java package com.cgiri.javabrains.spring4; import org.springframework.beans.factory.annotation.autowired; import org.springframework.context.applic...
Read more