字符串转NSData
NSData* postData = [content dataUsingEncoding:NSUTF8StringEncoding];
NSData转字符串
NSString* encryptString = [[NSString alloc]initWithData:encryptByts encoding:NSUTF8StringEncoding];
字典转NSData
NSData *prettyJson = [NSJSONSerialization dataWithJSONObject:dictionary options:NSJSONWritingPrettyPrinted error:nil];
NSData转字典
NSDictionary *myDictionary = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
数组转换成NSData
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dataArray options:NSJSONWritingPrettyPrinted error:nil];
