watch scope

[mvujica]

Probably not an issue but a caveat or I'm doing something wrong.
Inside watch function type of (this) is Vue so I have to do something like this or it won't compile:

// Watched class property @Watch plus declaration and initiation
    @Watch(function (newValue, oldValue) {
        let self = <AddressComponent>this;
        if (newValue == 0)
            self.isNewAddress = true;
        else
            self.isNewAddress = false;
    })
    selectedBillingAddress: string = undefined;

also data and watched members must be initialized.

[HerringtonDarkholme]

Thanks for filing this.

This is limitation of TypeScript's inference schema. Watch's annotation cannot have the annotated class's information.

Try this:

@Watch<AddressComponent, string>(function(newVal, oldVal){
  this.isNewAdress
})

[HerringtonDarkholme]

I might change the Watch function when microsoft/TypeScript#11929 is merged.

Then the Watch decorator will be like vue-typescript.

@Watch<MyComponent>('key')
myWatchMethod(newVal: string, oldVal: string) {

}
declare function Watch<V extends Vue>(key: keysof V): TypedProperty<(n: V[key], o: V[key]) => void>

User still needs to annotate Component class and value type, but the watch scope is correctly set to the enclosing class. And watch property type is checked.

[HerringtonDarkholme]

New style watch in next branch
/~https://github.com/HerringtonDarkholme/av-ts/tree/next

[mvujica]

Ok, next branch has it stringly typed like other libraries and vue, but I really like your strongly typed style, although it require additional annotation for "this" scope.

[HerringtonDarkholme]

Hi, it has a string API but everything is type checked! It's powered by typescript's new keyof and mapped type. We can achieve type safety without additional annotation

[mvujica]

Really nice, when do you plan to merge?

[HerringtonDarkholme]

Probably after typescript officially released mapped types in stable.

[whitetrefoil]

Watching on this issue...
Using this.$watch in mounted() until new TS release...

[HerringtonDarkholme]

Shipped in 0.6.0!