getClass(methods)
getClass()所属R语言包：methods
Get Class Definition
获取类定义
译者：生物统计家园网 机器人LoveR
描述----------Description----------
Get the definition of a class.
获取一个类的定义。
用法----------Usage----------
getClass(Class, .Force = FALSE, where)
getClassDef(Class, where, package, inherits = TRUE)
参数----------Arguments----------
参数：Class
the character-string name of the class, often with a "package" attribute as noted below under package.
类字符的字符串名称，往往与"package"下package属性，如注意到以下。
参数：.Force
if TRUE, return NULL if the class is undefined; otherwise, an undefined class results in an error.
如果TRUE，返回NULL如果类是不确定的;否则，在一个错误的未定义类的结果。
参数：where
environment from which to begin the search for the definition; by default, start at the top-level (global) environment and proceed through the search list.
环境，从开始定义搜索，默认情况下，开始在顶层（全局）环境，并继续通过搜索列表。
参数：package
the name of the package asserted to hold the definition. If it is a non-empty string it is used instead of where, as the first place to look for the class. Note that the package must be loaded but need not be attached. By default, the package attribute of the Class argument is used, if any. There will usually be a package attribute if Class comes from class(x) for some object.
包的名称断言举行的定义。如果它是一个非空的字符串，它是用来代替where，作为第一类的地方去寻找。请注意，必须装入包，但不必重视。包Class参数属性默认情况下，被使用，如果有的话。通常会有一个包属性，如果Classclass(x)一些对象。
参数：inherits
Should the class definition be retrieved from any enclosing environment and also from the cache? If FALSE only a definition in the environment where will be returned.
类的定义应该从任何封闭的环境，并从缓存中检索？如果FALSE只有在定义的环境where将被退回。
Details
详情----------Details----------
Class definitions are stored in metadata objects in a package namespace or other environment where they are defined. When packages are loaded, the class definitions in the package are cached in an internal table. Therefore, most calls to getClassDef will find the class in the cache or fail to find it at all, unless inherits is FALSE, in which case only the environment(s) defined by package or where are searched.
类定义存储在一个包中的命名空间或其他环境中定义它们的元数据对象。加载包时，包中的类定义是在一个内部表缓存。因此，大多数呼叫getClassDef将在缓存中找到类或未能找到它，inherits除非FALSE，在这种情况下，只有环境（S）的定义 package或where搜查。
The class cache allows for multiple definitions of the same class name in separate environments, with of course the limitation that the package attribute or package name must be provided in the call to
类缓存允许多个同一类的名称在不同的环境定义与限制，当然，必须在调用提供包属性或包名
值----------Value----------
The object defining the class. If the class definition is not found, getClassDef returns NULL, while getClass, which calls getClassDef, either generates an error or, if .Force is TRUE, returns a simple definition for the class. The latter case is used internally, but is not typically sensible in user code.
对象的定义类。如果未找到类定义，getClassDef回报NULL，而getClass，调用getClassDef，要么产生一个错误，或者如果.Force是TRUE，返回一个简单的定义为类。后者的情况下，内部使用，但通常不是明智的用户代码。
The non-null returned value is an object of class classRepresentation. For all reasonable purposes, use this object only to extract information, rather than trying to modify it: Use functions such as setClass and setIs to create or modify class definitions.
非空的返回值是一个对象类classRepresentation。对于所有合理的用途，使用此对象只提取信息，而不是试图修改它：如setClass和setIs创建或修改类定义的使用功能。
参考文献----------References----------
Software for Data Analysis: Programming with R Springer. (For the R version.)
Programming with Data Springer (For the original S4 version.)
参见----------See Also----------
Classes, setClass, isClass.
类，setClass，isClass。
举例----------Examples----------
getClass("numeric") ## a built in class[＃内置类]
cld <- getClass("thisIsAnUndefinedClass", .Force = TRUE)
cld ## a NULL prototype[＃一个NULL原型]
## If you are really curious:[＃如果你是真的很好奇：]
utils::str(cld)
## Whereas these generate errors:[＃鉴于这些产生错误：]
try(getClass("thisIsAnUndefinedClass"))
try(getClassDef("thisIsAnUndefinedClass"))
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注：
注1：为了方便大家学习，本文档为生物统计家园网机器人LoveR翻译而成，仅供个人R语言学习参考使用，生物统计家园保留版权。
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发表于 2012-2-16 19:12:21
