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Manipulate DB Objects

Creating objects

A new object can be created using the syntax DB.model.create().
As an example, suppose we have a model "person" with a field "name".
We would define a variable for the object, and initialise it as follows:
View XML:
main.xml
<view ...>
<var name="visitor" type="person" />
</view>
... and View JavaScript:
main.js
function init() {
view.visitor = DB.person.create();
view.visitor.name = "John";
}
All objects that are defined as variables in a view are saved automatically whenever a view is dismissed, but not when the user presses the back button. However, when defining an object only in JavaScript/TypeScript (and not in the view), you need to save the object manually:
JS
TS
main.js
var visitor = DB.person.create();
visitor.name = "John";
visitor.save();
main.ts
let visitor = await DB.person.create();
visitor.name = "John";
await visitor.save();

Setting datetimes

datetime fields are represented as the JavaScript/TypeScript Date type. To set a datetime to the current date and time, use new Date(). To set it to a specific time and date, use new Date(year, month, day, hour, minute, second). For more details, see this article at Mozilla.
Example:
main.js
view.current_time = new Date();

Setting dates

date fields are represented as a Day object. To set a date field to the current date, use new Day(). To set it to a specific date, use new Day(year, month, day).
Examples:
main.js
view.registration_date = new Day();
view.birthdate = new Day(1972, 3, 19);
var day = new Day("2014-01-05") // Parse some day.
var day = new Day(new Date()); // Convert Date to Day, in local timezone.
The Day object has additional functionality:
day.startOfDay(); // Start of day in local timezone, as a Date
day.endOfDay(); // End of day in local timezone, as a Date
day.toString(); // "2014-01-05"
day.toISOString(); // "2014-01-05"
day.toJSON(); // "2014-01-05"
day.valueOf(); // 1388880000000
day.getYear() // 2014
day.getMonth() // 0-11. January is 0, December is 11
day.getDay() // Day of the month (1-31).
day.getDayOfWeek() // Day of week (0-6). Sunday is 0, Saturday is 6.

Deleting objects

An object can be deleted using its destroy() function.
As an example, suppose we have a model "person":
View XML:
main.xml
<view ...>
<var name="visitor" type="person" />
</view>
... and View JavaScript:
main.js
view.person.destroy();

Setting relationships

Unlike fields, a relationship is set using a setter function.
As an example, suppose that in our Data Model every person is part of a household:
schema.xml
<data-model>
<model name="person">
<field name="name" type="text" />
<belongs-to model="household" />
<display>{name}</display>
</model>
<model name="household">
<field name="address" type="text" />
<has-many model="person" name="members" />
<display>{address}</display>
</model>
</data-model>
In our view we define our household and person:
main.xml
<view ...>
<var name="member" type="person" />
<var name="household" type="household" />
</view>
... and initialize them in JavaScript:
main.js
function init() {
view.household = DB.household.create();
view.member = DB.person.create();
view.member.household(view.household);
}
As you can see, we set the "household" relationship on the "member" by calling the household() function and passing the related "household" object as an argument.
As a more typical example, the household will be created in another view and passed as a parameter:
main.xml
<view ...>
<param name="household" type="household" />
<var name="member" type="person" />
</view>
... and the JavaScript:
main.js
function init() {
view.member = DB.person.create();
view.member.household(view.household);
}

Getting relationships

Getting a related object works that a particular object belongs to is done by calling a getter function, as seen below:
main.js
view.member.household();
Further Reading
When processing large datasets it is recommended to use batch operations. Please see the corresponding documentation here.