NSDate NSString NSArray NSDictionary 数据类型相互转换

NSString *string = @"hello word";
NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
NSArray *array = [NSArray arrayWithObjects:@"1",@"2",@"3",nil];
NSString *dateString = @"19891123";
NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:
                         @"hello", @"word",
                         @"chen", @"lu",
                         @"jin", @"mei",
                         @"cerastes", @"hehe",nil];

//NSString to NSData
    NSData *string2data = [string dataUsingEncoding:NSUTF8StringEncoding];
    NSLog(@"%@",string2data);

//NSData to NSString
    NSString *data2String = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"dataString = %@",data2String);    

//NSArray to NSData
    NSData *arry2data = [NSKeyedArchiver archivedDataWithRootObject:array];

//NSData to NSArray
    NSArray *data2arry = [NSKeyedUnarchiver unarchiveObjectWithData:arry2data];
    NSLog(@"%@  /n %@",arry2data,data2arry);

//NSString to NSDate
    NSDate *string2date = [self convertDateFromString:dateString withFormattre:@"yyyyMMdd"];
    NSLog(@"date = %@",string2date);

//NSDate to NSString
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSString *date2string = [dateFormatter stringFromDate:[NSDate date]];
    NSLog(@"%@", date2string);

//NSArray to NSString
    NSString *arry2String = [array componentsJoinedByString:@" "];
    NSLog(@"string = %@",arry2String);

//NSString to NSArray
    NSArray *string2Arry = [arry2String componentsSeparatedByString:@" "];
    NSLog(@" %@",string2Arry);

//NSDictionary to NSData:
    NSMutableData *dic2data = [[NSMutableData alloc] init];
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:dic2data];
    [archiver encodeObject:dic forKey:@"Some Key Value"];
    [archiver finishEncoding];
    NSLog(@"%@",dic2data);

//NSData to NSDictionary
    NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:dic2data];
    NSDictionary *data2dic = [unarchiver decodeObjectForKey:@"Some Key Value"];
    [unarchiver finishDecoding];
    NSLog(@"%@",data2dic);

//NSDictionary to NSString
    NSString *dic2string=[dic JSONRepresentation]; //这个方法是SBJson类库里的，需要导入SBJson.h
    NSLog(@"%@",dic2string);

//NSString to NSDictionary
    NSError *error = nil;
    NSDictionary *string2dic = [NSJSONSerialization JSONObjectWithData: [dic2string dataUsingEncoding:NSUTF8StringEncoding]
                                    options: NSJSONReadingMutableContainers
                                      error: &error];
    NSLog(@"%@",string2dic);