Vala DBus interface objects how should i register property changes?

Question

So when writing a vala interface for DBus it inherits from Object. yet, most of the properties are like this: public string name { owned get; } public string name { owned get; } as far as i can tell that means that Notify never fires if its value is changed (which i assume it can be, as it reflects an interface in dbus, which most certainly does change.)

sample:

[DBus (name ="org.bluez.Device1")]
public interface Device : Object{

    [DBus (name = "Connected")]
    public abstract bool connected { owned get; }

    [DBus (name = "Connect")]
    public abstract void connect();

    [DBus (name = "Disconnect")]
    public abstract void disconnect();    
}

public void print_device_status(Device device){
    if(device.connected){
        stdout.printf("Device is connected");
    }else{
        stdout.printf("device is disconnected!");
    }
}

int main(string[] args){

    string mac = "dev_14_A5_1A_7F_61_08";


    Device device = Bus.get_proxy_sync(BusType.SYSTEM, "org.bluez", string.join("/","/org/bluez/hci0", mac));

    string message = "";

    device.notify.connect(() => ( print_device_status(device) ));

    if(device.connected){
        device.disconnect();
    }

    device.connect();

    device.disconnect();

    return 0;
}

Compile command: valac --pkg gio-2.0 <file name> -o test

The connect and disconnect methods work as expected, print_device_status is never called. I can only assume it is because notify never fires, and I assume this is because there are no setters on the properties.

I know i can make DBusProxy objects and keep an eye on property changes in those, but that does not quite feel right either.

What is the 'correct' way to solve this?

Answer 1

You should check if that property emits a notification signal by calling org.freedesktop.DBus.Introspectable.Introspect , then you can connect to the org.freedesktop.DBus.Properties.PropertiesChanged DBus signal. More info in the official specification and the Vala samples