What interesting: if I define .then just as:.then(alert("in .then"));then it works fine. But if i use the function() inside or the notation you've provided:.then(output => {alert(output);});then system never reaches the .then. What I'm doing wrong?pt., 11 sty 2019 o 20:44 . <magicznykrag@gmail.com> napisał(a):Martin,Thank you very much for the answer! Unfortunately I'm still stuck :-( Please take a look at the following code and tell me why it's still asynchronous. It display properly messages: "testFunct" and then "end of testFunct", but it never reach the .then or .done.Thank you in advance!function testFunc() {alert("testFunc");lic = cockpit.spawn(["/usr/share/cockpit/testSoftware/connectExternalSystem"], {directory: "/usr/share/cockpit/testSoftware",err: "message"}).then(function() {alert("in .then of testFunc. Error: "+message);}).done(function() {alert("in .done of testFunc. Error: "+message);});alert("end of testFunc");}czw., 10 sty 2019 o 09:02 Martin Pitt <martin@piware.de> napisał(a):Hello Magik,
. [2019-01-09 21:51 +0100]:
> I'm C programmer learning now Cockpit. My problem is as follows: for some
> of the operation I must use external helper and I must wait for it output.
> The cockpit.spawn() function returns the promise, which is non-blocking
> operation (as expected). How can I make it work as blocking one? Which
> mean: the rest of the code in the function should be done after receiving
> full output of the cockpit.spawn (done() or fail())
This is a common pitfal when coming from the world of synchronous programming
languages (such as C or Python) and starting with asynchronous JavaScript.
Daniel's await proposal can certainly help to make async code look like it was
written in a sync style; but honestly, it's really best to let go of this
pattern when writing JS.
So instead of
output = cockpit.spawn(..).make_this_magically_sync();
followup_action(output);
actually use JavaScript promises as they are intended:
cockpit.spawn(..)
.then(output => {
followup_action(output);
})
.catch(err => {
console.error(err);
});
i. e. organize the stuff that depends on the result into promise handlers.
Martin
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