检索可观察值的当前值

Question

If I want to get the value of an observable, I typically call it as a function.

Say, I have a model with observables as below

export interface ClientModel {
    name: KnockoutObservable<string>;
    age: KnockoutObservable<number>;
}

And a model without observable as below

export interface ServerModel {
   name: string;
   age: number;
}

Below are two implementations of converting from one model to another.

A

export function getServerModelJson(person: ClientModel) : ServerModel {
   const personJson: ServerModel = {
      name: ko.unwrap(person.name),
      age: ko.unwrap(person.age)       
   }
   return personJson;
}

B

export function getServerModelJson(person: ClientModel) : ServerModel {
   const personJson: ServerModel = {
      name: person.name(),
      age: perosn.age()       
   }
   return personJson;
}

Is there a difference between the two (calling the observable as function versus using ko.unwrap). What is the recommended way? What changes if the fields are complex types. In those cases, how do you do the conversion?

Answer 1

Is there a different between the two (calling the observable as function versus using ko.unwrap ).

Two:

1. If you call the VM property as a function directly, it must be a function (eg, an observable or whatever). If it's a simple non-function data property, you'll get an error. With ko.unwrap , it gives you the simple non-function data property's value in that case (or, of course, the observable's value).

2. ko.unwrap adds a function call and a couple of checks (the call to ko.unwrap and the work it does to determine whether what you've passed it is an obserable).

If you know it's observable, as in your example, there's no real reason to use ko.unwap . (If you know it's not observable, similarly there's no real reason to use ko.unwrap .)

What is the recommended way?

It's up to you, based on what your properties are and whether you know they're observables.

What changes if the fields are complex types. In those cases, how do you do the conversion?

Nothing, you just do it the same way —note that if the properties of the complex type are also observables, you'll have to handle them separately ( ko.unwrap doesn't go deep).