node.js / postgres... asynchronous problem? - postgresql

Question

I have a list of types: ["type1", "type2, "type3"], on which I loop. For each type:
- create / execute a query to get the items of a the current type
- run another function when the query if done ( on('end') ).
for ( var i=0; i<types.length; i++ ){
type = types[i];
value = "test";
...
// ADD ITEM: QUERY
var query = client.query(...); // QUERY ITEMS OF A THE CURRENT TYPE
// ADD ITEM: ERROR CHECKING
query.on("error", function (err) {
...
});
with ({ t: type, v: value }) { // I HAD TO DO THAT SO THAT ALL THE TYPES ARE TAKEN INTO ACCOUNT
query.on('end', function() {
my_function(t, v);
});
}
}
my_function is like:
function my_function(type, value){
console.log(type + ',' + value); // CORRECT (I CAN SEE ALL THE TYPES BEEING LISTED)
// QUERY OTHER STUFF BASED ON THE VALUE OF "type"
var query = client.query(...);
// MAIN STUFF
query.on('row', function(row){
console.log(type + ',' + value); // THIS DOES NOT WORK ANYMORE... ONLY THE LAST TYPE IS TAKEN INTO ACCOUNT WHERE I EXPECT TO GET THIS MESSAGE FOR EACH TYPES.
...
}
// FINALIZE
query.on('end', function(){
...
}
}
I guess this is linked to asynchronous process... but cannot figure out where the error is.
UPDATE
I have updated my loop so it looks like:
for ( var i=0; i<types.length; i++ ){
type = types[i];
value = "test";
...
// ADD ITEM: QUERY
var query = client.query(...); // QUERY ITEMS OF A THE CURRENT TYPE
// ADD ITEM: ERROR CHECKING
query.on("error", function (err) {
...
});
// MAIN STUFF GOES HERE
(function(t, v) { query.on("end", function() {
console.log(t + ',' + v); // OK, I CAN SEE THIS DISPLAYED FOR EACH TYPE
my_function(t, v);
}); })(type, value);
}
I modified my_function so it looks like:
function my_function(type, value){
console.log(type + ',' + value); // OK, I CAN SEE THIS DISPLAYED FOR EACH TYPE
// QUERY OTHER STUFF BASED ON THE VALUE OF "type"
var query = client.query(...);
// MAIN STUFF
(function(t, v) {
query.on("row", function(row) {
console.log('TEST:' + t + ',' + v); // KO, I CAN ONLY SEE THIS DISPLAYED FOR ONE TYPE
}); })(type, value);
// FINALIZE
query.on('end', function(){
...
}
}

Answer 1

with ({ t: type, v: value }) { // I HAD TO DO THAT SO THAT ALL THE TYPES ARE TAKEN INTO ACCOUNT
query.on('end', function() {
my_function(t, v);
});
}
Is broken. What you want is this
query.on("end", my_function.bind(null, type, value));
Function.prototype.bind allows you to bind parameters to a function.
Never use with. An alternative that also works would be :
(function(t, v) {
query.on("end", function() { my_function(t, v); });
})(type, value);