Userdata allows arbitrary C data to be stored in variables.
用户数据允许在变量中任意存储C数据。
Of course, because the userdata originates in c, there are no pre-defined operations for userdata in Lua.
当然，由于用户数据源自于c，因此在Lua中也没有对用户数据预定义操作。
There are eight fundamental types (of values) in Lua: nil, Boolean, number, string, function, thread, table, and userdata.
Lua中的基本类型(值)有8种：nil，布尔型，数字，字符串，函数，线程，表以及用户数据。
You can even validate that document, and also refer to a given field using XPath (//user/userdata/field[@name='runningpace').
您甚至能够验证这个文档，也能够使用XPath (//user/userdata/field[@name='runningpace') 引用某一个域。
You can think of userdata as an array of bytes — bytes that might represent a pointer, a structure, or a file in the host application.
我们可以认为userdata就是一个字节数组——字节可以表示指针、结构或宿主应用程序中的文件。
Additional support exists for custom userdata objects, which can be defined by developers to handle types beyond those of the basic system.
另外，Lua还支持定制的userdata对象，开发人员可以通过定义userdata对象来处理基本类型以外的其他类型。
The value of "type" identifies the state change, but the userData value requires parsing to identify the process undergoing the change of state.
“type”值标识状态更改，但需要分析userdata值来确定进行状态更改的进程。
Because tables and userdata are so flexible, Lua permits you to overload operations for objects of either type. (you cannot overload the six other types.)
由于表和用户数据都非常灵活，因此Lua允许我们重载这两种类型的数据的操作(不能重载其他6种类型)。
Note that for websphere.ras notifications which contain a MessageEvent as the userData, we invoke the getLocalizedMessage simply to display a readable version of the actual notification data.
请注意，对于包含MessageEvent作为 userData的websphere.ras通知，要显示实际通知数据的可读版本，只需调用 getLocalizedMessage 即可。
Note that for websphere.ras notifications which contain a MessageEvent as the userData, we invoke the getLocalizedMessage simply to display a readable version of the actual notification data.
请注意，对于包含MessageEvent作为 userData的websphere.ras通知，要显示实际通知数据的可读版本，只需调用 getLocalizedMessage 即可。
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