CODEWITHSUNDEEP
c
samuelbrody1249
samuelbrody1249

Reputation: 4767

Directly accessing a union within a struct

Let's say I have the following tagged union:

typedef struct Form {
    FormType type;
    union {
        TaxForm tax; 
        BusinessForm bus; 
    } u;
} Form;

To access the main/sub object I have to do:

form->u.bus

Is there a way to either do:

form->u

Or:

form->bus

That is, to be able to access union object directly without going through its declarator (since by definition, the union will only have one item set).

Upvotes: 1

Views: 68

Answers (1)

M.M
M.M

Reputation: 141638

You can only do this by omitting the u from the original definition:

typedef struct Form {
    FormType type;
    union {
        TaxForm tax; 
        BusinessForm bus; 
    };  // <--- no u
} Form;

Then you can use form->bus and so on, where form is a pointer to Form .

This is called "anonymous unions" and was added in the C11 standard revision , so you will need to invoke your compiler in C11 or later mode, or hope that it supported this as an extension in older modes.

Upvotes: 2

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