JSON value in View Model displayed as [object Object] only - nativescript

Question

This will be a noob question. I am working on my first NativeScript app, a simple GPS tracker. It's only one view. I got the Location plugin to work and it outputs location data to the console nicely. It also seems to update the View Model. But when I try to bind it to a Label element's text, it only displays [object Object], regardless what I do.
The view model:
var observableModule = require("data/observable");
function viewModel() {
return new observableModule.fromObject({
"locations": [],
"lastLocation": {
"latitude": "0",
"longitude": "0",
"altitude": 0,
"horizontalAccuracy": 0,
"verticalAccuracy": 0,
"speed": "0",
"direction": "0",
"timestamp": new Date().toISOString()
},
"lastUpload": "Unknown"
});
}
module.exports = viewModel;
The view XML: (just the important part)
<Label text="Current location:"/>
<Label text="{{ lastLocation?.latitude }} ; {{ lastLocation?.longitude }}" />
<Label text="Last location update:"/>
<Label text="{{ lastLocation?.timestamp }}" />
<Label text="Last successful upload:"/>
<Label text="{{ lastUpload }}" />
The code:
var frameModule = require("ui/frame");
var viewModel = require("./home-view-model");
var geolocation = require("nativescript-geolocation");
var dialog = require("ui/dialogs");
var viewModel = new viewModel();
function onLoaded(args) {
page = args.object;
page.bindingContext = viewModel;
var enableLocation = new Promise((resolve, reject) => {
geolocation.enableLocationRequest(true)
.then(
success => resolve(),
error => reject(error)
)
})
.then(
() => {
watchId = geolocation.watchLocation(
function (loc) {
if (loc) {
viewModel.lastLocation = loc;
console.log(viewModel.lastLocation.latitude + ' ; ' + viewModel.lastLocation.longitude);
}
},
function (e) {
dialogsModule.alert('Location error: ' + e.message);
},
{
desiredAccuracy: 3,
updateDistance: 0,
minimumUpdateTime: 10000
})
},
error => {
dialogsModule.alert('Location error: ' + e.message);
}
)
}
exports.onLoaded = onLoaded;
The console.log row properly displays the latitude and longitude values. The view displays [object Object], but it displays the lastUpload value right. What am I doing wrong in the view?

Answer 1

Oh yes, it was a noob question. The solution is that I shouldn't use question marks in the template.
<Label text="Current location:"/>
<Label text="{{ lastLocation.latitude }} ; {{ lastLocation.longitude }}" />
<Label text="Last location update:"/>
<Label text="{{ lastLocation.timestamp }}" />
Now it works.