Question

当尝试在数字类型上使用@observable时，它不会创建Observable。这会导致每次获取计算值时重新计算的问题。除非输入已经改变，否则我不希望重新计算计算值，这里有什么问题？

https://jsbin.com/mofirujixu/1/edit?html,js,console

class Square {
  @observable width = 2;

  @computed get area() {
    console.log('calc area');
    return this.width * this.width;
  }
}

const square = new Square();
//prints out 'calc area' each time
console.log(square.area);
console.log(square.area);
console.log(square.area);

Answer 1

如果一个或多个观察者正在观察计算的结果值，则MobX仅缓存计算结果的值。它以这种方式实现，以减少内存占用并允许垃圾收集器完成其工作。

您可以在日志之前使用简单的autorun来查看此操作：

class Square {
  @observable width = 2;

  @computed get area() {
    console.log('calc area');
    return this.width * this.width;
  }
}

const square = new Square();

autorun(() => {
  square.area;
  // square.area is now observed by one observer, 
  // and will not be re-calculated for subsequent reads.
});
console.log(square.area);
console.log(square.area);
console.log(square.area);

数字类型的@observable不会创建observable

1 个答案: