Flex中的对象相等性是什么样的呢？国外有篇文章讨论了这一问题：Architectural Atrocities, part 8: is there no equality?

下面是我从Flex的参考手册中找出来的一些东西。

Equality operators

The equality operators take two operands, compare their values, and return a Boolean value. All the equality operators, as listed in the following table, have equal precedence:

The IUID interface defines the interface for objects that must have Unique Identifiers (UIDs) to uniquely identify the object. UIDs do not need to be universally unique for most uses in Flex. One exception is for messages send by data services.

Data providers and the uid property

Flex data provider controls use a unique identifier (UID) to track data items. Flex can automatically create and manage UIDs. However, there are circumstances when you must supply your own uid property by implementing the IUID interface, and there are circumstances when supplying your own uid property improves processing efficiency.

Because the Object and Array classes are dynamic, you normally do not do anything special for data objects whose items belong to these classes. However, you should consider implementing the IUID if your data object items belong to custom classes that you define.

Note: When Flex creates a UID for an object, such as an item in an ArrayCollection, it adds the UID as an mx_internal_uid property of the item. Flex creates mx_internal_uid properties for any objects that are dynamic and do not have bindable properties. To avoid having Flex create mx_internal_uid properties, the object class should do any of the following things: have at least one property with a [Bindable] metadata tag; implement the IUID interface; or have a uid property with a value.

If Flex must consider two or more different objects to be identical, the objects must implement the IUID interface so that you can assign the same uid value to multiple objects. A typical case where you must implement the IUID interface is an application that uses paged collections. As the cursor moves through the collection, a particular item might be pulled down from the server and released from memory repeatedly. Every time the item is pulled into memory, a new object is created to represent the item. If you need to compare items for equality, Flex should consider all objects that represent the same item to be the same “thing.”

More common than the case where you must implement the IUID interface is the case where you can improve processing efficiency by doing so. As a general rule, you do not implement the IUID interface if the data provider elements are members of dynamic classes. Flex can automatically create a uid property for these classes. There is still some inefficiency, however, so you might consider implementing the IUID interface if processing efficiency is particularly important.

In all other cases, Flex uses the Dictionary mechanism to manage the uid, which might not be as efficient as supplying your own UID.

Related posts:

1. 导出Memcached中的全部数据