Question

我的某些对象的实例有一些名为selected和方法select()的值。当触发方法select()时，我希望将对象的selected值设置为true，但此对象的所有其他实例的selected值为false - 怎么做？

换句话说 - 如何更改某个对象的所有实例的值？

    var Puzzel = function() {
        this.selected = false;
    }; 

    Puzzel.prototype = {            
        select: function{
            this.selected = true;
            //how to set selected = false on every other instance of Puzzel
        }
    }

Answer 1

如果您可以依赖getter / setter（请参阅compatibility），则以下内容将有效。

这种方法在选择或检查选择时会有不变的开销，并且会有恒定的内存开销。

var Selectable = function () {
  // Define your constructor normally.
  function Selectable() {
  }
  // Use a hidden variable to keep track of the selected item.
  // (This will prevent the selected item from being garbage collected as long
  // as the ctor is not collectible.)
  var selected = null;
  // Define a getter/setter property that is true only for the
  // item that is selected
  Object.defineProperty(Selectable.prototype, 'selected', {
    'get': function () { return this == selected; },
    // The setter makes sure the current value is selected when assigned
    // a truthy value, and makes sure the current value is not selected
    // when assigned a falsey value, but does minimal work otherwise.
    'set': function (newVal) {
      selected = newVal ? this : this == selected ? null : selected;
    }
  });
  // Define a select function that changes the current value to be selected.
  Selectable.prototype.select = function () { this.selected = true; };
  // Export the constructor.
  return Selectable;
}();

Answer 2

您需要跟踪这些实例。这是一种方法：

(function() {
    var instances = [];
    window.MyClass = function() {
        instances.push(this);
        // rest of constructor function
    };
    window.MyClass.prototype.select = function() {
        for( var i=0, l=instances.length; i<l; i++) instances[i].selected = false;
        this.selected = true;
    };
})();

JS - 更改对象的所有实例的值

2 个答案: