NSString学习

1. UTF8String   这个方法将NSString转为C语言中以'\0'结尾的字符串.

　　　　Returns a null-terminated UTF8 representation of the receiver.

　　　　- (const char *)UTF8String

　　　　Return Value

　　　　A null-terminated UTF8 representation of the receiver.

　　　　Discussion

　　　　The returned C string is automatically freed just as a returned object would be released; you should copy the C string if it needs to store it outside of the autorelease context in which the C string is created.