structs

This is a discussion on structs within the C Programming forums, part of the General Programming Boards category; hey guys just wondering how i could access a member from the structure definitions below but access it from a ...

  1. #1
    Musicman - Canora
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    structs

    hey guys just wondering how i could access a member from the structure definitions below but access it from a function called systemInit like the one below.

    iv tried going menu->PriceType->dollars; but that wont work it says there is no member.

    And 1 other question if i needed to intialize the struct members which ones would i need to initialize this eventually is also going to be used for linked lists?

    Code:
    typedef struct category* CategoryTypePtr;
    typedef struct item* ItemTypePtr;
    
    /* Structure definitions. */
    typedef struct price
    {
       unsigned dollars;
       unsigned cents;
    } PriceType;
    
    typedef struct item
    {
       char itemID[ID_LEN + 1];
       char itemName[MAX_NAME_LEN + 1];
       PriceType prices[NUM_PRICES];
       char itemDescription[MAX_DESC_LEN];
       ItemTypePtr nextItem;
    } ItemType;
    
    typedef struct category
    {
       char categoryID[ID_LEN + 1];
       char categoryName[MAX_NAME_LEN + 1];
       char drinkType;      /* (H)ot or (C)old. */
       char categoryDescription[MAX_DESC_LEN];
       CategoryTypePtr nextCategory;
       ItemTypePtr headItem;
       unsigned numItems;
    } CategoryType;
    
    typedef struct gjc
    {
       CategoryTypePtr headCategory;
       unsigned numCategories;
    } GJCType;
    Code:
    void systemInit(GJCType* menu)
    {
    }

  2. #2
    Registered User vinit's Avatar
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    try this menu->headCategory->headitem->prices[index].dollars

  3. #3
    Registered User 00Sven's Avatar
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    You need to go with the actual name of the variable because PriceType is the type so it would be
    menu->headCategory->headItem->prices[somenumberhere]->dollars
    ~Sven
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    On an output stream, fflush causes any buffered but unwritten data to be written; On an input stream, the effect is undefined. It returns EOF for a write error, and zero otherwise. fflush(NULL) flushes all output streams.
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  4. #4
    Musicman - Canora
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    i get headitem that there is no member

  5. #5
    Musicman - Canora
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    it works but how come when i go ->dollars it dosnt like the -> instead i have to put the

    full stop .dollars im using ansi c on unix

  6. #6
    Registered User ssharish2005's Avatar
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    remember the use 0f -> is when u access the structure members using a pointer of type that structure

    and . is used when access the structure members using a normal variable of type that structure

    for example
    Code:
    struct somename
    {
         int somedata1;
         int somedara2;
    };
    
    //using normal varibale
    struct somename name;
    
    //uisng structure pointer
    struct somename *nameptr;
    
    //access that data
    name.somedata1;
    name.somedata2;
    
    nameptr->somedata1;
    nameptr->somedata2;
    ssharish2005

  7. #7
    Musicman - Canora
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    also mate if i declare the member like this
    menu->headCategory->headItem->prices[somenumberhere]->dollars = 0

    how come i get a segmentation error?

  8. #8
    Registered User ssharish2005's Avatar
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    what is your array size
    Code:
    PriceType prices[NUM_PRICES];
    i mean NUM_PRICES value ->????

    it seems that u crossing the array boundary

    ssharish2005

  9. #9
    Musicman - Canora
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    the array size of NUM_PRICES is 3

  10. #10
    Registered User ssharish2005's Avatar
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    so what is the value of somenumberhere -> ???

    if this is more than 3 u might well get some error like SEG FAULT

    ssharish2005

  11. #11
    Musicman - Canora
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    menu->headCategory->headItem->prices[3]->dollars = 0

    thats how it is but i get a seg fault

  12. #12
    ZuK
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    given the declarations from the first post
    Code:
    menu->headCategory->headItem->prices[somenumberhere]->dollars = 0
    shouldn't compile
    Kurt

  13. #13
    Musicman - Canora
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    menu->headCategory->headItem->prices[somenumberhere].dollars = 0

    i changed it to this and now it does compile

  14. #14
    ZuK
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    I know.

  15. #15
    Musicman - Canora
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    but why when i runnit do i get a seg fault

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