️ C Language structure realizes simple address book ( Static version )

Preface ：

On the structure 、 After the learning of user-defined types such as enumeration , Then try to use structure and other related knowledge to realize simple address book . Due to C Linguistic GUI Interface failed to understand , So the address book implemented this time is only a very simple address book , The address book has a static version , Dynamic Edition , Today, the document version mainly realizes the static version

Front row reminders ： Because it involves code implementation and ideas , Article slightly longer , Students who don't look at ideas can also directly move to the code warehouse to check the source code ！

: To view the detailed code, please move to the warehouse -------> Address book code

Code overview + Results display

️ Code overview

// Code display in the main file 
int main()
{
	int input = 0;
	Contact_people con; // Use the address book structure to create a file named con The address book of 
	Init_Contact(&con);  // Perform encapsulation initialization 
	do
	{
		menu();
		printf(" Please select  >");
		scanf("%d", &input);
		switch (input)
		{
		case 0:
			printf(" Exit address book \n");
			break;
		case 1:
			Add(&con);   
			break;
		case 2:
			Del(&con);
			break;
		case 3:
			Search_Contact(&con);
			break;
		case 4:
			Modify_Contact(&con);
			break;
		case 5:
			Show_Contact(&con);
			break;
		case 6:
			Sort_Contact(&con);
			break;
		default:
			printf(" Input error , Please re-enter \n");
			break;
		}
	} while (input);
	return 0;
}

// Code display in header file 
// Create a structure to represent the information of people in the address book 
typedef struct PeInfo 
{
    
	char name[20];  
	int age;
	char tele[12];
	char sex[10];
	char addr[20];
}PeInfo;    //
// Create a structure to encapsulate the information and quantity of people in the address book 
typedef struct Contact_people
{
    
	PeInfo message[100];
	int num;
}Contact_people;

// Initialize function declaration 
void Init_Contact(struct Contact_people* pc);

// Add human information function declaration 
void Add(struct Contact_people* pc);

// Display human information function declaration 
void Show_Contact(struct Contact_people* pc);

// Find people's information function declaration 
void Search_Contact(struct Contact_people* pc);

// Delete the human information function declaration 
void Del(struct Contact_people* pc);

// Modify people's information function declaration 
void Modify_Contact(struct Contact_people* pc);

// Sort people's information 
void Sort_Contact(struct Contact_people* pc);

️ Part of the results show

Realize the idea

In that case , Then how to achieve the final effect step by step ？

1、 Create an address book using a structure

The first consideration is what type we can use to create an address book , In the traditional sense int、float And other data types are definitely not feasible . Can we directly use character array to create address book ？ The answer is also no ！ After all, a person's information is not single , He has a name 、 Age 、 Telephone 、 Home address . We need to integrate the information of the same person , Achieve modularity .

We can use structure nesting to create address book

typedef struct PeInfo 
{
    
	char name[20];  
	int age;
	char tele[12];
	char sex[10];
	char addr[20];
}PeInfo; 
// Create a structure to encapsulate the information and quantity of people in the address book 
typedef struct Contact_people
{
    
	PeInfo message[100];
	int num; // Record the number of people in the current address book 
}Contact_people;

// So let's create one PeInfo The type of structure , This structure stores the basic information of people 
// Create another Contact_people The type of structure ,; Used to indicate address book , At the same time, human information can be summed up 

2、 Print the directory for the user to select and initialize the created address book

After creating the structure type in the header file , You can create an address book through this structure type in the source file , And after creating the type It must be initialized in time

Use do----while Realize the repeated printing of the directory , Use switch ----case The choice of statement implementation function

// Initialization function , Use memset Function to initialize memory 
void Init_Contact(struct Contact_people* pc)
{
    
	assert(pc); // If pc If it is a null pointer, an error is reported 
	pc->num = 0;
	memset(pc->message, 0, sizeof(pc->message)); //  utilize memset Function initializes a known address 
}

3、 Realize each function one by one

When implementing these functions, we should pay attention to

①： The address book is created with structural variables , At the same time, structure nesting is realized , Therefore, when visiting the members of the structure, we should clarify the relationship between them , At the same time, use structure members to access operators （ Arrow operator and point operator ） To change the data

	printf(" Please enter the name of the person you want to add >:");
	scanf("%s", pc->message[pc->num].name);
// If in Add When you need to add a name to the function , You should call first Contact_People Medium message member , because message Is an array , Re pass num Find the corresponding person , And then again 
// Access through the dot operator PeInfo Medium name

②： When realizing the sorting function , Use qsort function To sort names , You should know more about qsort Function is used to realize the sorting method you want

int cmp_by_name(const void* e1, const void* e2)
{
    
	return strcmp(((PeInfo*)e1)->name,((PeInfo*)e2)->name);
}
void Sort_Contact(struct Contact_people* pc)
{
    
	assert(pc);  // If pc If it is a null pointer, an error is reported 
	if (0 == pc->num)
	{
    
		printf(" Address book is empty , Cannot sort ！\n");
		return;
	}
	else
	{
    
		qsort(pc->message, pc->num, sizeof(PeInfo), cmp_by_name);  // there qsort The function needs attention 
		printf(" Sorting succeeded ！\n"); 
	}
}

Learning experience summary

In the process of implementing the address book , I went further to Structure , Nested structure ,memset function ,qsort function ,strcmp function And the modular operation of sub files, etc. have a further understanding .

1、 When designing pointer transfer parameters , Should be used more assert（） To assert formal parameters , Preventive cause NULL And cause misoperation

2、 When there is too much code , File splitting operation should be carried out , Separate the declaration and implementation of functions , Ensure that the corresponding header file and the source file have the same name