NSData和NSString的相互转化

『导言』

iOS 开发中如何使NSData和NSSting相互转化？

str转data：initWithData: encoding:
data转str：dataUsingEncoding:

• NSString ->NSData

• 方法：dataUsingEncoding:

    NSString *str = @"username=zwj&pwd=123&type=JSON";
    NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
    NSLog(@"\nstr = %@\n-------\n data = %@\n",str,data);

• 打印结果str->data

     str = username=zwj&pwd=123&type=JSON
     data = <75736572 6e616d65 3d7a776a 26707764 3d313233 26747970 653d4a53 4f4e>

• NSData -> NSString

• 方法：initWithData: encoding:

    NSString *str2 = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"\n data = %@\n ---------\n  ,str2 = %@ \n ",data,str2 );

• 打印结果 data->str

    data = <75736572 6e616d65 3d7a776a 26707764 3d313233 26747970 653d4a53 4f4e>
    ,str2 = username=zwj&pwd=123&type=JSON