tailieunhanh - HandBooks Professional Java-C-Scrip-SQL part 115

Tham khảo tài liệu 'handbooks professional java-c-scrip-sql part 115', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Sets the isa pointer of the receiver to classObj and returns the previous value of the pointer. This effectively converts the receiver to an instance of the class represented by classObj. This will only work if the receiver s class is a descendant of the class represented by classObj and instances of the two classes have the same size. If the call fails it returns nil. Enforcing intentions Each method in the following list generates a runtime error. In each case when you call the method pass in the _cmd variable which the runtime sets up to be the selector of the method you are in. - id subclassResponsibility SEL sel Call this in a method that you require subclasses to override and implement. - id notImplemented SEL sel Call this in a method that you have deliberately left unfinished. - id shouldNotImplement SEL sel Call this in a method that you inherit and override but that makes no sense for your subclass to support. Error handling The following functions are used for error handling. See Section for more information about their usage. - id doesNotRecognize SEL sel Generates a runtime error by invoking the -error method on self. The runtime sends this message to an object when the object has failed to respond to or forward a message. - id error const char format . Writes an error message to the system log via the syslog call and exits the program. The runtime calls this method on self for a variety of error conditions. Override as described in Section to customize error handling for a class. Archiving The GNU runtime provides the type TypedStream for reading and writing objects to and from archives. Section describes this type and its use in saving and restoring objects. The following methods support archiving - id awake Does nothing and returns self. Called by the runtime when an object has been reconstructed. Override to customize behavior when your objects are restored. - id write TypedStream stream Writes the receiver