How to define own map keys like :bluetooth, :wifi

Thanks. So sadly I can use them only rarely because most keys I use are also used for persistance already. But at least some keys can be optimised

Accessing by symbol may not be as efficient as using an index, and memory wise, would be a simple object, like a Number.

In the line of code you posted, that would also crash on a device without wifi, as :wifi doesn't exist on those.

Documentation says, that if the device does not support e.g. wifi, connectionInfo[:wifi] will return null. Yes, my example would crash but what you see sounds like following would crash also:

var connectionInfo = settings.connectionInfo;
var supportsBluetooth = connectionInfo[:bluetooth] != null;
var supportsWifi = connectionInfo[:wifi] != null;
var supportsLTE = connectionInfo[:lte] != null;

var stateBluetoothIsConnected = supportsBluetooth && connectionInfo[:bluetooth].state == System.CONNECTION_STATE_CONNECTED;
var stateNetworkIsConnected = (supportsWifi && connectionInfo[:wifi].state == System.CONNECTION_STATE_CONNECTED) ||
							(supportsLTE && connectionInfo[:lte].state == System.CONNECTION_STATE_CONNECTED);

It works in the emulator although the fenix 6x does not support LTE...

Michael said:

Thanks. So sadly I can use them only rarely because most keys I use are also used for persistance already. But at least some keys can be optimised

Well...

I asked a question here that I think is relevant to read through: https://forums.garmin.com/developer/connect-iq/f/q-a/218088/is-there-a-better-way-to-select-resources

The outcome was a way better understanding by me of how symbols work and a revolutionary understanding of how to get memory down AND improve the readability of my code.

For example:

If, in Strings, I define a string for state label (Rez.Strings.Stopped,Rez.Strings.Paused,Rez.Strings.Running) and those have settings that go with them, I can do something like this:

//////////////
// In initialize
fgColours = {};
fgColours[:Stopped] = Graphics.COLOR_RED;
fgColours[:Paused] = Graphics.COLOR_ORANGE;
fgColours[:Running] = Graphics.COLOR_GREEN;

bgColours = {};
bgColours[:Stopped] = Graphics.COLOR_BLACK;
bgColours[:Paused] = Graphics.COLOR_GREY;
bgColours[:Running] = Graphics.COLOR_WHITE;

///////////////////
// In compute...
if(aTestYouWrote) { currentState = :Running; }
else if(someOtherTestYouWrote) { currentState = :Paused;    }
else {  currentState = :Stopped; }

// In onUpdate, use state to set foreground, background and label
var stateLabel = WatchUI.loadResource(Rez.Strings[currentState]);
dc.setColor(fgColours[currentState],bgColours[currentState]);
dc.clear();
dc.drawText(tx.ty,stateLabel,font,5);
// Additional display code to customise for each state... 
if(currentState == :Running) {
    // Running display
    
} else if(currentState == :Paused) {
    // Paused display
} else {
    // Stopped display
}

Now, obviously, that's pseudo code and there are ways to make it more efficient / smaller / better, but the concept is that a readable Symbol used in code means I can load exactly what I want with minimal code and it is easy to both read and to manage linked strings, JSON resources, image resources etc.

For built-in objects, I think you're meant to use "has" to check that it allows that property before checking it is null.

On devices that don't allow it, even reading the property can cause a crash.

One thing to note about "has" (since we're talking about symbols), is that I advice using it sparingly, as it's not a simple operation.  IT's got to look around for the symbol.

Do it once when an app starts and set a boolean, as it won't be changing at runtime and no need to use it on every call to onUpdate() for example.

var supportsLTE = connectionInfo[:lte] != null;

This would be false on a f6x

and there is a much simpler way to set stateNetworkIsConnected 

var sSettings=Sys.getDeviceSettings();

hasConnectionAvail=(sSettings has :connectionAvailable); //this only needs to be done when the app starts

var stateNetworkIsConnected==(hasConnectionAvail) ? sSettings.connectionAvailable : sSettings.phoneConnected;

This works on any device to see if the device is connected to something

for 

bgColours = {};
bgColours[:Stopped] = Graphics.COLOR_BLACK;
bgColours[:Paused] = Graphics.COLOR_GREY;
bgColours[:Running] = Graphics.COLOR_WHITE;

you can replace that with 1 line:

bgColours={:Stopped=>Graphics.COLOR_BLACK,:Paused=>Graphics.COLOR_GRAY,:Running=>Graphic.COLOR_WHITE};

or to be more efficient,

enum {

  STOPPED,PAUSED,RUNNING

}

and then 

bgColours=[Graphics.COLOR_BLACK,Graphics.COLOR_GRAY,Graphic.COLOR_WHITE];

and to reference something,

bgColours[RUNNING]

for example  A simple array of numbers vs a dictionary.

thanks for all the tipps, I'll use them to optimise my watchfaces memory usage