Re: [algogeeks] How to identify what is stored in union in c language

Tue, 22 Feb 2011 07:45:40 -0800 

Then it should be:
struct UserData
{
     uType m_dataType;
     union {
          int m_intValue;
          float m_floatValue;
          char m_charValue;
     };
} data;



On 2011-2-22 15:29, Rajiv Podar wrote:

Hi Shiva,
There is no as such way to know what type of value is stored in the Union (as per my knowledge) 
But you can try the following code in order to keep track.

enum { INT, FLOAT, CHAR } uType;

union UserData
{
     uType m_dataType;
     int m_intValue;
     float m_floatValue;
     char m_charValue;
}; data
So whoever update the UserData union he should update the uType variable as well and while accessing the value following trick can be used: 

if (m_charValue.m_dataType== INT)
        printf("%d\n",data.m_intValue);
    if (m_charValue.m_dataType== FLOAT)
        printf("%f\n",data.m_floatValue);
    if (m_charValue.m_dataType== CHAR)
        printf("%c\n",data.m_charValue);
    else
        printf("bad type %d in utype\n", utype);


I hope this will solve your case.


Thanks & Regards,
Rajiv Podar
On Tue, Feb 22, 2011 at 12:15 PM, shiva <[email protected] <mailto:[email protected]>> wrote: 

    I have an union with following members

    union data
    {
    int age;
    char grade;
    }var;

    now after some operation which assign value to var(it can assign it
    either age or grade), is there any way i can identify whether var
    contain age or grade now.

    Thanks for the comments..

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