Vuex getter not updating

问题:

I have the below getter:

withEarmarks: state => {
    var count = 0;
    for (let l of state.laptops) {
        if (l.earmarks.length > 0) {
            count++;
        }
    }
  return count;
}

And in a component, this computed property derived from that getter:

    withEarmarks() { return this.$store.getters.withEarmarks; },

The value returned is correct, until I change an element within the laptops array, and then the getter doesn't update.

回答1:

In your case state.laptops.earmarks is an array, and you are manipulating it by its array index state.laptops[index]. Vue is unable to react to mutations on state arrays (by index). The documentation provides 2 workarounds for this:

// 1. use purpose built vue method:
Vue.set(state.laptops, index, laptop)

// 2. splice the value in at an index:
state.laptops.splice(index, 1, laptop)

Although it is documented, I'm thinking a giant neon glowing sign on that page that says "You will waste hours of productivity if you don't know this" would be a nice addition.

You can read more about this "caveat" here: https://vuejs.org/v2/guide/list.html#Caveats