Passing Structs to the Functions

Functions can work with structures just like with regular variables:

main


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#include <stdio.h>

// structure definition
typedef struct {
    char name[50];
} Person;

// function to display information about a person
void printPerson(Person p) {
    printf("Name: %s\n", p.name);
}

int main() {
    // creating a structure and initializing its values
    Person person1 = {"John"};

    // call a function to display information about a person
    printPerson(person1);

    return 0;
}

In order for a function to "interact" with a structure, for example, change the fields of an existing structure, the function must accept a pointer to the structure:

main


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#include <stdio.h>

// structure definition
Typedef struct {
    char symbol;
}Example;

// function for changing the values of structure fields via a pointer
void changePoint(Example* ptr, int newSymbol)
{
    // check for NULL pointer
    if (ptr != NULL)
    {
        ptr->symbol = newSymbol;
    }
}

int main() {
    // create the Example structure and a pointer
    Example ptr1 = {'H'};
    Example* ptr = &ptr1;

    printf("Old symbol: %c | %p\n", ptr1.symbol, &ptr1);

    // use function to change the field of structures
    changePoint(ptr, 'y');

    printf("New symbol: %c | %p\n", ptr1.symbol, &ptr1);

    return 0;
}

Structures can be created inside functions, and such structures can "live" outside the functions (not locally) if the function returns a pointer to such a structure:

main


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#include <stdio.h>
#include <stdlib.h>

// structure definition
typedef struct {
    int value;
}Example;

// function creates a structure with the given field
Example* CreateStruct(int setVal)
{
    Example* ptr = (Example*)malloc(sizeof(Example));

    // check for successful memory allocation
    if (ptr != NULL)
    {
        ptr->value = setVal;
        return ptr;
    }
}

int main() 
{
    // use function to create structure 
    Example* ptrToStruct = CreateStruct(23);

    printf("Value inside struct: %d", ptrToStruct->value);

    free(ptrToStruct); // free memory

    return 0;
}

Opgave

Swipe to start coding

Provide the correct return type and args of the function
Inside function create a pointer variable and allocate memory for your structure;
Сreate a pointer to store the address returned by the function;
Displaying the info about your person;
Free up the allocated memory.

Løsning

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Var alt klart?

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Sektion 2. Kapitel 5

Passing Structs to the Functions

Functions can work with structures just like with regular variables:

main


              123456789101112131415161718192021
            
#include <stdio.h>

// structure definition
typedef struct {
    char name[50];
} Person;

// function to display information about a person
void printPerson(Person p) {
    printf("Name: %s\n", p.name);
}

int main() {
    // creating a structure and initializing its values
    Person person1 = {"John"};

    // call a function to display information about a person
    printPerson(person1);

    return 0;
}

In order for a function to "interact" with a structure, for example, change the fields of an existing structure, the function must accept a pointer to the structure:

main


              12345678910111213141516171819202122232425262728293031
            
#include <stdio.h>

// structure definition
Typedef struct {
    char symbol;
}Example;

// function for changing the values of structure fields via a pointer
void changePoint(Example* ptr, int newSymbol)
{
    // check for NULL pointer
    if (ptr != NULL)
    {
        ptr->symbol = newSymbol;
    }
}

int main() {
    // create the Example structure and a pointer
    Example ptr1 = {'H'};
    Example* ptr = &ptr1;

    printf("Old symbol: %c | %p\n", ptr1.symbol, &ptr1);

    // use function to change the field of structures
    changePoint(ptr, 'y');

    printf("New symbol: %c | %p\n", ptr1.symbol, &ptr1);

    return 0;
}

Structures can be created inside functions, and such structures can "live" outside the functions (not locally) if the function returns a pointer to such a structure:

main


              1234567891011121314151617181920212223242526272829303132
            
#include <stdio.h>
#include <stdlib.h>

// structure definition
typedef struct {
    int value;
}Example;

// function creates a structure with the given field
Example* CreateStruct(int setVal)
{
    Example* ptr = (Example*)malloc(sizeof(Example));

    // check for successful memory allocation
    if (ptr != NULL)
    {
        ptr->value = setVal;
        return ptr;
    }
}

int main() 
{
    // use function to create structure 
    Example* ptrToStruct = CreateStruct(23);

    printf("Value inside struct: %d", ptrToStruct->value);

    free(ptrToStruct); // free memory

    return 0;
}

Opgave

Swipe to start coding

Provide the correct return type and args of the function
Inside function create a pointer variable and allocate memory for your structure;
Сreate a pointer to store the address returned by the function;
Displaying the info about your person;
Free up the allocated memory.

Løsning

Skift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder

Var alt klart?

Tak for dine kommentarer!

Sektion 2. Kapitel 5

Skift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder