dependency-observable.md

Dependency observable

Dependency observables make it easy to automatically update observable which is constructed from another observable. Let's take a look at examples with the two types of dependency observables.

Read-only dependency observable

Read only dependency observables are created by providing a function to the blocks.observable() method. The framework will automatically detect which observables are used by immediately calling the function.

var firstName = blocks.observable('John');
var lastName = blocks.observable('Doe');
var fullName = blocks.observable(function () {
  return firstName() + ' ' + lastName();
});

Read-write dependency observable

There are some cases when you need a read\write dependency observable to control more complex scenarios. You could create such an observable by passing an object with get() and set() methods to the blocks.observable() method.

var firstName = blocks.observable('John');
var lastName = blocks.observable('Doe');
var fullName = blocks.observable({
  get: function () {
    return firstName() + ' ' + lastName();
  },

  set: function (value) {
    var splits = value.split(' ');
    firstName(value[0]);
    lastName(value[1]);
  }
});