how to connect C++ signal to QML handler

[mzimmers]

@LeLev said in how to connect C++ signal to QML handler:

this will not refresh, you will always see the initial value of synthName.

OK, so this is what I needed to know. So...a property will update automatically, where a reference to a function will not, right? Thanks, LeLev.

[ODБOï]

@mzimmers that is true.

[ODБOï]

@mzimmers hi again,

sorry i misread your initial code.. i did not see that you declare getSynthName() in QML also ..

In this case i would simply do this :

text: issViewModel.synthName !== "" ? issViewModel.synthName : "No Synthesis Loaded"

no need the js function.

[mzimmers]

Actually, I cleaned that up a little. I have a couple of utility JS functions now:

  function getNoSynthName() {
    var name =  "No Synthesis Loaded"
    return name;
  }
    function getSynthName() {
      var name = issViewModel.synthName
      if (name === "") {
          name = getNoSynthName()
      }
      return name;
  }

This is the only location that uses the function in issViewModel. This allows me to do this in another area:

 StyledButton {
   visible: Utils.getSynthName() !== Utils.getNoSynthName()
...

[ODБOï]

@mzimmers said in how to connect C++ signal to QML handler:

visible: Utils.getSynthName() !== Utils.getNoSynthName()

This will be evaluated only single time, you can test it and correct me if i'm wrong.

@mzimmers said in how to connect C++ signal to QML handler:

Actually, I cleaned that up a little. I have a couple of utility JS functions now:
function getNoSynthName() {
var name = "No Synthesis Loaded"
return name;
}
function getSynthName() {
var name = issViewModel.synthName
if (name === "") {
name = getNoSynthName()
}
return name;
}

This is the only location that uses the function in issViewModel. This allows me to do this in another area:
StyledButton {
visible: Utils.getSynthName() !== Utils.getNoSynthName()
...

You could replace all that by this single line that will hide the Styled Button button if the synthName == "" . And it will be reevaluated every time synthName changes...

 StyledButton {
    visible:  issViewModel.synthName

[mzimmers]

@LeLev said in how to connect C++ signal to QML handler:

@mzimmers said in how to connect C++ signal to QML handler:

visible: Utils.getSynthName() !== Utils.getNoSynthName()

This will be evaluated only single time, you can test it and correct me if i'm wrong.

It seems to update. At app startup, the button isn't visible. When I load a synthesis and return to this screen, the button is visible. The nature of the app is such that once something is loaded, it never returns to an "unloaded" state, so I can't fully test this, but it does update (at least once).

@mzimmers said in how to connect C++ signal to QML handler:

Actually, I cleaned that up a little. I have a couple of utility JS functions now:
function getNoSynthName() {
var name = "No Synthesis Loaded"
return name;
}
function getSynthName() {
var name = issViewModel.synthName
if (name === "") {
name = getNoSynthName()
}
return name;
}

This is the only location that uses the function in issViewModel. This allows me to do this in another area:
StyledButton {
visible: Utils.getSynthName() !== Utils.getNoSynthName()
...

You could replace all that by this single line that will hide the Styled Button button if the synthName == "" . And it will be reevaluated every time synthName changes...

 StyledButton {
    visible:  issViewModel.synthName

Not quite. When no synthesis is loaded, I need that value "No Synthesis Loaded" because I use it in two screens.

[ODБOï]

@mzimmers said in how to connect C++ signal to QML handler:

Not quite. When no synthesis is loaded, I need that value "No Synthesis Loaded" because I use it in two screens.

if you need the functions in other places then use them, but in this particular case when you write

 StyledButton {
   visible: Utils.getSynthName() !== Utils.getNoSynthName()

you are hiding that button if synthName == ""

This does the same, but is much simpler.

StyledButton {
    visible:  issViewModel.synthName

[mzimmers]

@LeLev I suppose it's a matter of coding taste. I personally don't care to implicitly determine a boolean based on the contents of a string (or any other variable; I prefer the comparison to be made explicitly. More verbose, but (IMO) easier for the new reader to understand. I do appreciate the input, though.

[ODБOï]

@mzimmers said in how to connect C++ signal to QML handler:

I prefer the comparison to be made explicitly

you can write it in more explicit way, to me this is simpler

StyledButton {
    visible:  issViewModel.synthName != ""

than

StyledButton {
    visible:  Utils.getSynthName() !== Utils.getNoSynthName()  

@mzimmers said in how to connect C++ signal to QML handler:

I suppose it's a matter of coding taste.

To me it is not just a mater of taste.
you are calling 2/3 functions where you could just write one simple js expression...

Also because one solution will update/refresh dynamically but the other will not
[edit] i was wrong here, actually both solution will update, as explained by @GrecKo

[GrecKo]

@LeLev said in how to connect C++ signal to QML handler:

Also because one solution will update/refresh dynamically but the other will not
visible: issViewModel.synthName != "" // this will update dinamially
visible: Utils.getSynthName() !== Utils.getNoSynthName() // this will not update dinamially.Only evaluated 1 time on component creation

That's incorrect. Both will updated dynamically since the functions are evaluated in QML. Were the functions implemented in C++, the QML would have no way to figure out the properties dependencies but that that's not the case here.