Thread: struct-property name is in char*

You can't really do that in C. You'd need something more like this:

Code:

struct test
{
    char *name;
    int data;
} t;

...do stuff...

if( strcmp( t.name, "test" ) == 0 )
{
    t.data = 10;
}

You can't really address structures by a string name. Meaning, you can't do:

Code:

printf( "What is the name of your structure? " );
fflush( stdout );
fgets( structurename, BUFSIZ, stdin );

structurename.x = 10;

You can't do that last line. You need to wrap it somehow (ie: store the name of 'structurename' some place in an actual structure, and then go fetch it (as showin in the first segment above)).


Quzah.

There is no such thing in C.

You would have to write your own code to solve that. How you would do that and what the best solution is, depends a little bit on what your structur(es) look like and what your application needs to do.

You can't really use switch either.

Here's a solution that may work:

Code:

struct somestruct
{
    int x;
    int y;
    int z;
};

struct propentry
{
    ptrdiff_t offset;
    const char *name;
};

#define PE(a) { offsetof(somestruct, a), #a }

struct propentry proptable[] = 
{
    PE(x),
    PE(y),
    PE(z)
};

int getProperty(char *name, somestruct *astruct)
{
    int i;
    for(i = 0; i < sizeof(proptable)/sizeof(proptable[0]); i++)
    {
        if (strcmp(proptable[i].name, name) == 0)
        {
             int *ptr = (int *)(((char *)astruct) + proptable[i].offset);
             return *ptr;
        }
    }
    return -1;
}

I haven't tried to compile the code, so it may not work 100% straight out of the box, but it's showing the principle fairly well.

It gets even more complicated if the content is not all integers, of course...

--
Mats

It is missing struct in front of somestruct in a few places.

The cast is casting a pointer to somestruct into char * - so that we can add the offset.

I just copied and pasted the code into an editor and fixed up the errors and added a main to test it out, and it work.

However, if you are a beginner, I'm not sure if you actually SHOULD be doing this. You are probably doing something wrong if you feel that you need to use this.

--
Mats

I agree, please describe the problem, not how to fix your solution.