increaseCount : function () { if (!this.food.count) { this.food.count = 1 this.food.$set('count', 1) // 这里应该这么设置才有效 console.log(this.food) // Object {count: 1, __ob__: Observer} } else { this.food.count ++ }

props should be immutable.
The data state is variable.
And Vue.set dynamically sets the properties of the object, and this object should also exist in data.

｛ data() { return { food: { } } }， methods: { increase() { Vue.set(this.food, 'count', 1); }, }, ｝