Objective - C学习（Foundation框架）-- 02类

NSString NSMutableString
NSArray NSMutableArray
NSSet　NSMutableSet
NSDictionary NSMutableDictionary
NSDate
NSObject

C -> OC字符串
NSString *s = [[NSString alloc] initWithUTF8String:"jake"];

OC -> C
const char *cs = [s UTF8String];
NSUTF8StringEncoding 中文转码