iOS (NSData、NSString、NSDictionary、NSArray互转 )

1.NSData转换为NSString、NSDictionary和NSArray

NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];  
NSString *result = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];   

NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];  
NSDictionary *responseObject = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingMutableContainers error:&error];  

NSData *data = [NSKeyedArchiver archivedDataWithRootObject:array];  
NSArray *array = [NSKeyedUnarchiver unarchiveObjectWithData:data];   

2.NSString、NSDictionary和NSArray转换为NSData

NSString *string = @"I am a String";    
NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];  

NSDictionary *dic = @{@"name": @"Jerry", @"age": @"24"};  
NSData *data = [NSJSONSerialization dataWithJSONObject:dic options:NSJSONWritingPrettyPrinted error:nil];  

NSArray *array = [[NSArray alloc]initWithObjects:@"0",@"1",nil];  
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:array];