I have been trying to print to multiple printers with QZ tray using the examples provided here https://qz.io/wiki/2.0-Raw-Printing#promise-loop
but I am getting an error saying TypeError: Cannot read property 'sendData' of null
I have rsvp-3.1.0.min.js
, sha-256.min.js
and qz-tray.js
included.
I use the exact same code provided by the example but obviously changed the printers names to the ones I have installed.
Everything works fine if I try to print to each printer separately (the default way of doing it)
Any idea of what could be wrong or if I am missing a library or something?
Thank you
This is the full error message on Safari:
TypeError: Cannot read property 'sendData' of null
at qz-tray.js:323
at lib$rsvp$$internal$$initializePromise (rsvp-3.1.0.min.js:10)
at new lib$rsvp$promise$$Promise (rsvp-3.1.0.min.js:10)
at Object.promise (qz-tray.js:456)
at Object.dataPromise (qz-tray.js:314)
at Object.find (qz-tray.js:788)
at link (test.html:388)
at lib$rsvp$$internal$$tryCatch (rsvp-3.1.0.min.js:10)
at lib$rsvp$$internal$$invokeCallback (rsvp-3.1.0.min.js:10)
at rsvp-3.1.0.min.js:10
So I found the problem and it was my own mistake, I forgot to initiate QZ tray, the script works perfectly, tested sending a Pixel job to a laser printer and a Raw job to a thermal printer.
EDIT: Solution
function promiseLoop() {
var data = [
"^XA\n^FO50,50^ADN,36,20^FDPRINT 1 ^FS\n^XZ\n",
"^XA\n^FO50,50^ADN,36,20^FDPRINT 2 ^FS\n^XZ\n",
"^XA\n^FO50,50^ADN,36,20^FDPRINT 3 ^FS\n^XZ\n",
"^XA\n^FO50,50^ADN,36,20^FDPRINT 4 ^FS\n^XZ\n"
];
var configs = [
{ "printer": "ZDesigner LP2844-Z" },
{ "printer": "ZDesigner LP2844-Z" },
{ "printer": "ZDesigner LP2844-Z" },
{ "printer": "ZDesigner LP2844-Z" }
];
var chain = [];
for(var i = 0; i < data.length; i++) {
(function(i_) {
//setup this chain link
var link = function() {
return qz.printers.find(configs[i_].printer).then(function(found) {
return qz.print(qz.configs.create(found), [data[i_]]);
});
};
chain.push(link);
})(i);
//closure ensures this promise's concept of `i` doesn't change
}
//can be .connect or `Promise.resolve()`, etc
var firstLink = new RSVP.Promise(function(r, e) { r(); });
var lastLink = null;
chain.reduce(function(sequence, link) {
lastLink = sequence.then(link);
return lastLink;
}, firstLink);
//this will be the very last link in the chain
lastLink.catch(function(err) {
console.error(err);
});
}
//Always make sure you are establishing a connection before printing
qz.websocket.connect().then(promiseLoop).catch(errorHandler);