Promise how to implement in this situation?
i have a problem with sync using fs.readfile, they are not inicializing at the first time, if i try request again, then i have results. I know i can use promise and i find something useful with Q from Kriskowal. I tried it but without success. I didn´t understand very well how to implement it. If someone can help with this, i will be eternally grateful.
code:
"use strict"
var Q = require('q');
var fs = require('fs');
var arrayZipBand = [];
var jsonZipCode = [];
var arrayParsedZipcodeBr = [];
exports.parse = function(opts) {
if (opts.zipBand.constructor != Array) {
opts.zipBand = [opts.zipBand];
}
if (opts.location.constructor != Array) {
opts.location = [opts.location];
}
if (opts.config === 0) {
opts.zipBand.forEach(function(file) {
fs.readFile(file, 'utf8', function(err, logData) {
if (err) throw err;
let text = logData.toString();
decodeURIComponent(text);
let lines = text.split('n');
lines.forEach(function(line) {
let parts = line.split('@');
if (parts[1] != undefined) {
let obJson = {
LOC_NU: parts[0],
LOC_CEP_INI: parts[1],
LOC_CEP_FIM: parts[2]
}
arrayZipBand.push(obJson);
}
});
});
});
opts.location.forEach(function(file) {
fs.readFile(file, 'utf8', function(err, logData) {
if (err) throw err;
let text = logData.toString();
decodeURIComponent(text);
let lines = text.split('n');
lines.forEach(function(line) {
let parts = line.split('@');
if (parts[1] != undefined) {
for (let i = 0; i < arrayZipBand.length; i++) {
if (parts[0] == arrayZipBand[i].LOC_NU) {
jsonZipCode.push(arrayZipBand[i]);
}
}
if (jsonZipCode === undefined) {
throw "Was not possible to find Zipcode for the id " + parts[0];
}
for (let i = 0; i < jsonZipCode.length; i++) {
let obJson = {
LOC_NU: parts[0],
UFE_SG: parts[1],
LOC_NO: parts[2],
MUN_NU: parts[8],
LOC_CEP_INI: jsonZipCode[i].LOC_CEP_INI,
LOC_CEP_FIM: jsonZipCode[i].LOC_CEP_FIM
}
arrayParsedZipcodeBr.push(obJson);
}
jsonZipCode = [];
}
});
});
});
};
return arrayParsedZipcodeBr;
}
uhm it seems you are trying to read files in the loop cycle then, but in a async way. First question, is why async reading those files? You can always read them in sync way:
var data=fs.readFileSync(fname, encoding);
By the way, if you wish to read them async and keep the for...loop you need something like a Promise, or a timed wait or a more complex synchronization mechanism.
You can keep it simple, without using any other packages/modules in this way:
/**
* Promise.All
* @param items Array of objects
* @param block Function block(item,index,resolve,reject)
* @param done Function Success block
* @param fail Function Failure block
* @example
promiseAll(["a","b","c"],
function(item,index,resolve,reject) {
MyApp.call(item,function(result) {
resolve(result);
},
function( error ) { reject(error); }):
},
function(result) { // aggregated results
},function(error) { // error
})
* @author Loreto Parisi (loretoparisi at gmail dot com)
*/
promiseAll: function(items, block, done, fail) {
var self = this;
var promises = [],
index = 0;
items.forEach(function(item) {
promises.push(function(item, i) {
return new Promise(function(resolve, reject) {
if (block) {
block.apply(this, [item, index, resolve, reject]);
}
});
}(item, ++index))
});
Promise.all(promises).then(function AcceptHandler(results) {
if (done) done(results);
}, function ErrorHandler(error) {
if (fail) fail(error);
});
}, //promiseAll
so you can call it like
promiseAll(arrayOfItems, function(item, index, resolve, reject) {
// do something on item
if (someSuccessCondOnThisItem) {
resolve(item)
} else {
reject(new Error("operation failed"))
}
}, function(results) { // aggregated results
console.log("All done %d", results.length);
}, function(error) { // error
console.log(error.toString());
});
Keep in mind that this is a very simplified approach, but in most of cases it works when cycling through arrays.
Here is a simple working example in the playground:
var console = {
log : function(s) { document.getElementById("console").innerHTML+=s+"<br/>"}
}
var promiseAll= function(items, block, done, fail) {
var self = this;
var promises = [],
index = 0;
items.forEach(function(item) {
promises.push(function(item, i) {
return new Promise(function(resolve, reject) {
if (block) {
block.apply(this, [item, index, resolve, reject]);
}
});
}(item, ++index))
});
Promise.all(promises).then(function AcceptHandler(results) {
if (done) done(results);
}, function ErrorHandler(error) {
if (fail) fail(error);
});
}; //promiseAll
arr=[1,2,3]
promiseAll(arr
,function(item,index,resolve,reject) {
console.log("Resolving item[" + index+"]")
var okCond=true
if(okCond) {resolve(item)} else { reject(new Error("item[" + index+"]")) }
}
,function(results) { // aggregated results
console.log("All done of "+results.length);
}
,function(error) { // error
console.log(error);
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